PRESENT’S OFFICE, REGIONAL ADMINISTRATION

AND LOCAL GOVERNMENT

SECONDARY EXAMINATION SERIES

CHEMISTRY FORM FOUR 

MID-TERM EXAMS – AUG/SEPT – 2024

TIME: 2:30 HRS

INSTRUCTIONS 

1.  Thus paper consists of section A, B and C with total of  eleven (11) questions
2.  Answer all questions
3.  All writing must be in blue or Black in except drawing which must be in pencil
4.  Section A and C carry fifteen (15) marks
5.  Cellular phones and any unauthorized material are not allowed in assessment room

 SECTION A

Answer all questions in this section

1.               For each of the items (i) - (x) choose the correct answer from the given alternatives and its letter in the answer sheet provided.

1. Zinc reacts with dilute acids displacing hydrogen, but copper does not. This indicates that; -

1.              Zinc is higher in the activity series than hydrogen and copper
2.               Zinc is less reactive than copper
3.              Copper is more electropositive than zinc
4.             Copper is inert
5.               Copper is found above zinc and hydrogen in the electrochemical series.

2. The reason that made scientists to stop using hydrogen gas in filling balloons is; -

1.              The gas became denser than air
2.               The gas is less dense than air
3.              Discovery of helium gas
4.             The gas is soluble in water
5.               The gas is highly flammable and burns with pop sound.

3. What fire extinguisher will you use to help your friend whose shirt caught fire during an experiment in the laboratory?

1.              Powder fire extinguisher
2.               Fire blanket
3.              Carbon dioxide
4.             Water
5.               Foam.

4. The nuclide notation of element Z is ₁₅³¹Z which set of sub-atomic particles is collect?

1.              15 protons, electrons 16, and 15 neutrons
2.               15 protons,15 electrons, and 16 neutrons
3.              15 protons, 15 electrons and 15 neutrons
4.             16 protons, 16 electrons and 15 neutrons
5.               16 protons, 15 electrons, and 15 neutrons

5. A form four student was given the following staffs for preparation of ammonia gas.

1.                  Source of heat
2.                 Calcium hydroxide
3.                  Ammonium chloride
4.                 Solid potassium hydroxide

6. A rapid chemical reaction that release energy in form of light and heat is called; -

1.              Neutralization
2.               Decomposition
3.              Combustion
4.             Precipitation
5.               Displacement

7. Which of the following pairs constitute the best methods for treating and purifying water?

1.              Chlorination and distillation
2.               Chlorination and sedimentation
3.              Disinfection and decantation
4.             Disinfection and filtration
5.               Chlorination and aeration

8. The equation below shows the dissociation of sulphuric acid into ions: -

H₂SO_4(aq)       H⁺ _(aq)  + SO4^2- _(aq). From the equation, how many ions are there in 9.8g of   H₂SO₄?

1.              2.9x10²³ ions
2.               1.22x 10²³ions
3.              8.9 x10²³ions
4.             1.81x10²³ions
5.               0.3x10²³ions

9. Why oxygen differs from other gases?

1.              It explodes and support combustion
2.               It neither burns nor support combustion
3.              It burns but does not support combustion
4.             It supports combustion but does not burn
5.               It burns and support combustion

10. In the following equilibrium equation

the forward reaction is exothermic. Which change would increase the production of Sulphur trioxide at equilibrium?

1.              Adding a catalyst
2.               Decreasing pressure
3.              Increasing temperature
4.             Decreasing Sulphur trioxide concentration
5.               Decreasing temperature

2.               Match the items in list A with the correct response in List B by writing the letter of the correct response in the box provided bellow

SECTION B (54 marks)

Answer all questions in this section

3.               (a) Form four students wanted to verify the presences of water in an unknown compound using hydrated copper (II) sulphate. A small amount of hydrated copper (II) sulphate was placed on watch glass followed by addition of few drops of the unknown compound. Then was no change in the colour observed.

1.                  Why was there was no change in the colour of hydrated copper (II) sulphate?
2.               What other substance that could be in the place of the hydrated copper (II) sulphate to observe the required colour change.

(b) What is so called the universal solvent comment on this statement

4. Chemistry teacher guided students of form four to study carefully an experiment carried out in order to distinguish various substances formed during an experiment. The procedures were as follows

1.                                    Measure about 120cm3 of water and pour it in a beaker
2.          Add a spatula full of common salts and stir to allow salts to dissolve
3.                                    Continue to add more salts to the solution, stirring until no more salts can dissolve
4.          Place the solution on tripod stand and heat gently as you continue stirring
5.                                    Stop heating when salts dissolves
6.                                     Place the beaker in a trough of cold water and allow cooling for 3 to minutes note the results observed
   1.                                                   What type of solution was obtained when a spatula full of table salt were dissolved in 120 cm3 of water at room temperature?   Give reasons
   2.          What type of solution was obtained when no more salts dissolved in cold water at room temperature? Give reason
   3.           What is the name of the final solution obtained after cooling through of coldwater? Give reason
   4.              Explain the two (2) application of the concept studied above

5. Mwasiti was supplied with two beakers, one containing 0.1M KOH standard solution, and the other beaker containing sulphuric acid solution whose molarity was not known.  She was asked to find the molarity of the acidic solution. Mwasiti took the basic solution and put it into the burette, then she measured accurately 25cm³ of sulphuric acid using a measuring cylinder and transferred it into a conical flask, she is then added few drops of methyl orange indicator.

Her titration results were showing that 25cm³ of acid required 2cm³ of KOH standard solution.

She used the following formula to calculate the molarity of the sulphuric acid.

Molarity of H₂SO₄ acid = (Volume of acid   x   Volume of base)/Molarity of base

(a) What are the mistakes Mwasiti performed in her titration? (Four mistake).

(b) For each mistake, suggest the correct measure you would take.

6. (a) A person suffering from in digest ion produces1.0Litre of gastric juices per day which contains about 2.0g of hydrochloric acid. How many antacid tablets each containing 400mmg of sodium bicarbonate (NaHco3) is needed to neutralize all the hydrochloric acid produced in a day?

2.                                Name the suitable warning sign that you would find on the following: -

1. A bottle containing concentrated sulphur in a day?
2. A bag contain ingrator insect poison
3. Room door containing x–ray machine
4. Bag containing dynamites

7. Explain how the following factors affect the rate of chemical reaction

1.                                               Pressure (ii) Temperature

2.          Sodium hydroxide was dissolved in water after a while the container. Holding the solution was observed to be hat
   1.                                Basing on the heat change, name there action that took place in the above process
   2.         Suggest any two application of  there action above in our everyday
   3.       Draw energy level diagram for the above process named in b(i)

8. During electrolysis of an aqueous of salt of metal X, a current of 2.0A was passed for 26 minutes and 32 seconds. The mass of metal ‘X’ deposited was 0.24g.

1. On which electrode was the metal X deposited?
2. Calculate the amount of charge needed to deposit 1 mole of metal X.
3. Calculate the charge carried on the ion.
4. Write an ionic equation to show how the ions of the metal X are discharged at the electrode (R.A.M. of metal X= 24)

SECTIONC (30 MARKS)

Answeronlytwo(02) questionsfromthissection.

9. Agriculture is back bone of our economy but the addition of in organic fertilizers in the farm is not as important as addition of organic manure. Discuss the correctness of this statement in four points.

10. The extraction of metals has economic advantageous in Tanzania, but it’s still destructive to the environment. Illustrate three (3) environmental destructions may be caused by the process, and suggest three (3) control measure to problem.

11. (a)Name the process used to obtain an aqueous solution of ethanol from a sugar, for example Glucose (C₆H₁₂O₆)

(b) States without further description, the method you would use to obtain a sample of reasonably pure ethanol from the aqueous solution, and indicate the physical properties to which this separation in based.

 (c) Briefly explain the following chemical reaction which takes place when: -

1. Ethanol burns in air with a pale blue flame.
2. Sodium is added to a pure ethanol; a colorless gas is evolved.

PRESIDENT’S OFFICE, REGIONAL ADMINISTRATION AND LOCAL GOVERNMENT

SECONDARY EXAMINATION SERIES,

PRE- MOCK CHEMISTRY FORM FOUR

Time: 3Hours

Instructions 

1.         This paper consists of sections A, B, and C with a total eleven (11) questions.
2.         Answer all question in the sections A, B and two (2) questions from section C.
3.         Section A carries sixteen (16) marks, section B fifty four (54) marks and section C carries thirty (30) marks.
4.         All writing should be in blue or black pen, except for diagrams that must be drawn in pencil.
5.         Communication devices and any unauthorized materials are not allowed in the examination room.
6.         Write your Examination Number on every page of your answer booklet (s)

SECTION A.

1.         For each of the following items  (i-x).Choose the correct answer from given alternatives and writer its letter besides the item number in the answer booklet

1.            Which type of bonding is expected in a compound formed between potassium (K) and chlorine (Cl)?

1.        Ionic
2.         Covalent
3.         Metallic
4.        Hydrogen Bonding
5.          Dipole-Dipole Interactions

2.          The mass number of an atom represents the total number of:

1.        Protons only
2.         Neutrons only
3.         Electrons only
4.        Protons and neutrons
5.          Protons and electrons

3.        How many moles of carbon dioxide (CO2) are present in 88 grams of CO2?

1.        0.5 moles
2.         1 mole
3.         2 moles
4.        4 moles
5.          88 moles

4.        When heating a flammable liquid in a laboratory, which of the following is the safest practice?

1.        Direct heating with a Bunsen burner
2.         Heating in a water bath
3.         Heating in an open test tube
4.        Adding flammable liquids to an open flame
5.          Leaving the experiment unattended

5.          Which separation technique would be most appropriate for separating a mixture of water and ethanol?

1.        Filtration
2.         Chromatography
3.         Simple distillation
4.        Fractional distillation
5.          Evaporation

6.        During the electrolysis of molten sodium chloride (NaCl), which of the following substances is formed at the cathode?

1.        Chlorine gas (Cl₂)
2.         Sodium metal (Na)
3.         Hydrogen gas (H₂)
4.        Oxygen gas (O₂)
5.          Hydrochloric acid (HCl)

7.      For a reversible reaction, a large value of the equilibrium constant (Kc) indicates that:

1.        The reaction proceeds very slowly
2.         The forward reaction is favored
3.         The reverse reaction is favored
4.        The reaction is at equilibrium
5.          The reaction does not take place

8.   Which metal is commonly extracted from its oxide ore using electrolysis?

1.        Iron (Fe)
2.         Gold (Au)
3.         Sodium (Na)
4.        Copper (Cu)
5.          Zinc (Zn)

9.        Chlorine reacts with sodium hydroxide (NaOH) to form a common household disinfectant. What is the main active ingredient in this disinfectant?

1.        Hydrochloric acid (HCl)
2.         Sodium chlorate (NaClO₃)
3.         Sodium hypochlorite (NaClO)
4.        Sodium chloride (NaCl)
5.          Sodium chlorite (NaClO₂)

10.          Which type of reaction is most characteristic of saturated hydrocarbons?

1.        Substitution
2.         Addition
3.         Polymerization
4.        Condensation
5.          Combustion

2. Match the compound in LIST A with the correct way to identify it in LIST B and write the letter of the correct answer on sheet provided.

SECTION B: 54 Marks

3(a) State two reasons why we use the non-luminous flame for heating in a laboratory instead of using the luminous flame.                             

(b) Chlorine has two isotopes with atomic mass 35 and X occurring in the ratio 3:1 respectively. The relative atomic (R.M.A) of chlorine is 35.5. Determine the value of X.                            

(c) In an experiment to electroplate iron with silver, current of 1 Ampere was passed through a silver solution of ions for 60 minutes.  

(i) Give a reason why it is necessary to electroplate iron.                                       

(ii) Calculate the mass of silver deposited on iron during the electroplating process. (Ag = 108, IF = 96500c)

4. (a) Calculate the volume of 0.6M sulphuric (VI) acid solution needed to neutralize 30cm³ of 0.2Mpotassium hydroxide.                                                                                                                 

(b) A state of equilibrium between dichromate (vi) and chromate ions is established as shown below

Cr₂O₇²⁻ (aq) + H₂O (l) ⇌ 2 CrO₄²⁻ (aq) + 2 H⁺ (aq)

Orange                                    (Yellow)

i. What is meant by dynamic equilibrium?                      

ii. State and explain observation made, when a few pellets of Potassium Hydroxide are added to equilibrium mixture                                                          

(c ) The following reaction takes place in a closed system:

N₂(g) + 3H₂(g) ⇌ 2NH₃(g) ΔH = -92 kJ/mol

Consider the following scenarios:

Scenario 1: More nitrogen (N₂) gas is added to the system.

Scenario 2: The temperature of the system is decreased.

Scenario 3 A catalysts is added to the system.

For each scenario:

a) Predict the direction in which the equilibrium will shift (left, right, or no change). b) Explain your reasoning using the principles of chemical equilibrium and Le Chatelier's principle.

5. Use the diagram below to answer the questions that follow. 

(a) Identify the substances labelled R, S, K and P                                                      (b) What is the function of the part labelled P?                                                     

(c) Write half equations at the electrodes.                                                           

(d) Why is molten sodium chloride used instead of sodium chloride solution?   

(e) Why is calcium chloride added in the electrolysis of molten sodium chloride?

(f) How is the calcium eventually separated from the sodium?                             

(g) When sodium is left exposed in the air a white solid is formed but when sodium is burnt in oxygen, a yellow solid is formed.  Explain this difference using equations.              

6. Use the information in the table below to answer the questions that follow.  The letters do not represent the actual symbols of the elements.                                        

(a) Give a reason why the melting point of;

(i) S is higher than that of R.                                                                          

(ii) V is lower than that of U.                                                    (b) How does the reactivity of W with chlorine compare with that of R with chlorine?

 (c) When 0.30g or R was reacted with water 1600cm³ of gas was produced.  Determine the relative atomic mass of R.  (Molar gas volume = 24000cm³ r.t.p

(d) Give one use of element V.                                                                  

(e) Draw a structure of the compound formed when S reacts with U.                 

(f) Compare the atomic radius of element S and V.  Give a reason

7. (a) Hard water has both advantages and disadvantages. Give one advantage and one disadvantage of using hard water                                                                      

 (b) Using an equation, explain how addition of sodium carbonate is used to remove water hardness.                                                                                                               

(c) Outline three importance of a chemical equation.

8. I. In an experiment, copper metal was heated in the air to form a black solid T. dilute Sulphuric (VI) acid was then added to solid T resulting to formation of solution W, after which Ammonia was then added to solution W drop wise till excess

(a) Identify solid T         

 (b)Write a chemical equation for the reaction leading to formation of solution W                                                                                                                                                           

 (c) State the observations made when the ammonia solution was added to solution W dropwise till excess.                                                                                    

II. Substance A is a solid that does not conduct electricity at room temperature. However, when molten, it becomes a good electrical conductor.

Substance B is a solid with a high melting point and can conduct electricity in the solid state.

a) Suggest the likely types of bonding present in Substance A and Substance B. 

b) Explain the differences in their electrical conductivity in both solid and molten/liquid states.

(c) An experiment is set up to electrolyze a concentrated solution of sodium bromide (NaBr).

i) Identify the products that would form at the cathode and anode. 

ii) Explain your reasoning, including relevant half-equations. 

iii) Describe any observable changes expected during the electrolysis process.

SECTION B: 30 MARKS

Answer any two questions

9.(a) What name is given to each of the following?

(i) Ability of a metal to be beaten/ hammered to a sheet    

 (ii)Force of attraction that holds two molecules together    

 (b) When 3.1g of Copper {II} Carbonate were heated in a crucible until no further change in mass, solid L and gas M were formed

(i) Identify solid L and gas M       

(ii) Write a chemical equation for the reaction that occurred   

(iii) Given Cu=64, C=12,O=16, calculate the mass of the solid L that was formed                                                                                                                                                                          

10 (a) Give the name of the following processes.

 (i) A hot saturated solution of copper (II) sulphate is cooled to form crystals of copper (II) sulphate.

 (ii)A white powder is formed when concentrated sulphuric (V) acid is added to blue hydrated copper

(II) sulphate.                                                                                                       

(b)Study the flow chart below and answer the questions that follow.

(i) Name substances: B, C, D, and Solid E                                                                

(ii) Write equations for the reactions in steps; III and V

(iii) Write the ionic equation for the reaction in step II.                                             

 (iv) State any two observations made in step I.                                             

11. (a) Addition of inorganic fertilizers in the farm is not as important as addition of organic manure. Discuss the correctness of this statement in four (4) points

(b) Soil fertility and soil productivity are mistakenly used to mean the same concept. How do they differ from each other? Give five points

PRESIDENT’S OFFICE, REGIONAL ADMINISTRATION AND LOCAL GOVERNMENT

SECONDARY EXAMINATION SERIES,

MID TERM ONE – MARCH-2024

CHEMISTRY FORM FOUR

Time: 3Hours

Instructions 

1.         This paper consists of sections A, B, and C with a total eleven (11) questions.
2.         Answer all question in the sections A, B and two (2) questions from section C.
3.         Section A carries sixteen (16) marks, section B fifty four (54) marks and section C carries thirty (30) marks.
4.         All writing should be in blue or black pen, except for diagrams that must be drawn in pencil.
5.         Communication devices and any unauthorized materials are not allowed in the examination room.
6.         Write your Examination Number on every page of your answer booklet (s

SECTION A.

Answer all questions in this section. 

1.         For each of the following items  (i-x).Choose the correct answer from given alternatives and writer its letter besides the item number in the answer booklet provided

1.     An increase in temperature of a gas in enclosed system container caused an increase pressure of the gas. This is because it increases the ;

1. Number of gas molecule
2. Combination of gas  molecule
3. Number of collision between gas molecules
4. Average velocity of gas molecules
5. Kinetic energy of gas particles

2.  1.4g of potassium hydroxide is dissolved in water to form 250cm³ of solution. What is the molarity of the solution

1. 0.001M
2. 0.1M
3. 1.4M
4. 5.6M
5. 6.0M

3.                         When methane undergoes substitution reaction with excess chlorine, What is the final product?

1. Chloromethane
2. Dichloromethane
3. Tetrachloroethane
4. Tetrachloromethane
5. Monochloromethane

4.                         Ethanol reaction with ethanoic  acid  to form a group of organic compound called

1. Alkynes
2. Halo-alkanes
3. Esters
4. Alkenes
5. Alkanes

5.   Insoluble salts like Barium Sulphate generally can be obtained in laboratory by;

1. Evaporation of its concentrated solution
2. Crystallization
3. Precipitation
4. Decomposition
5. Displacement

6.                         In a blast fumace carbon monoxide is prepared by passing carbon dioxide over red hot coke. What is the chemical role of carbon dioxide

1. An acceleration
2. An oxidizing agent
3. Reducing agent
4. A catalyst
5. Oxidized

7.    What is the oxidation number of Phosphorus in the following compound? H₃PO₄

1. -5
2. 0
3. ⁺2
4. ⁺5
5. ^-3

8.  Which of the following is not an organic compound?

1. CO
2. C₆H₁₂O₆
3. CH₄
4. CH₃COOH
5. C₂H₅B₁

9.                         A metal Nitrate which will not give a metal oxide on heating is

1. Calcium Nitrate
2. Silver Nitrate
3. Lead Nitrate
4. Copper Nitrate
5. Zink Nitrate

10.   What action should be taken immediately after concentrated Sulphuric acid is spilled on the skin

1. It should be rinsed off with large amount of water
2. It should be neutralized using concentrated NaOH
3. The affected area should be wrapped tightly and shown to a medical health provider
4. It should be neutralized using solid CaCO₃
5. It should be neutralized with concentrated KOH

2.         Match sources of energy in the list A with corresponding description in list B. Write letter of the correct answer beside item number

SECTION B 

54 MARKS

Answer all questions 

3.         (a) Study the following reaction equation N_2(g)+3H_2(g)   H = -46.2KJlmo1^-1

Use le chateliers Principle, suggest how you would use temperature and pressure to obtain the highest production of ammonium in equilibrium 

(b) The formation of methane from hydrogen and carbon monoxide can be represented by:

CO_{(g) +}2H_2g           CH₃OH        DH= 91KJ.........

What mass of hydrogen would cause heat change of 91KJ?

4.         What is the importance of having fume chamber in Chemistry Laboratory

(ii) Why do laboratory doors open outwards?

(b) State the use of following item in first aid 

1.     Cotton wool
2.  Petroleum jelly
3.      Pain killers
4.       Bandage
5.   Razor blade

5.         Define the following terms;

1.     Molecular formula
2.  Empirical formula

(b) You are provided with compound 22.2%Zuric, 11.6% Sulphur, and 22.3%. Oxygen and the rest water of Crystallization. Calculate the molecular formula of the compound if its molecular mass is 283.

6.         16.8g of impure potassium hydroxide was dissolved in distilled water to make 1000mls. 20mls of this solution required 28mls of 0.07M saulphuric acid to react. Calculate :

(a) molarity of KOH

(b) Mass concentration of pure KOH 

7.         (a) The modern periodic law is based modification of Mendeleev periodic law. Explain how the two theories differ from each other.

(b) Comment on the following statement

(i) Lithium has large size than beryllium 

(ii) Sodium is smaller than Potassium 

(c) gives any four ions whose electronic configuration resemble that of Neon.

8.         (a) state faradays maw of electrolysis

Using the law state above, derive mathematical expression of Faradays first law of electrolysis. 

(b) How many moles of electrons will be transferred is Zinc metal is produced by a current of 14.23A. Supplied for 8.0hrs.

SECTION C

30 MARKS

Answer 2 questions from this section.

9.         With aid of balanced chemical equation; explain the process that occurs in blast fumace during extraction of irons.
10.    (a) define the following terms

1.     Functional group
2.  Homologous series
3.      Isomerism

(b) Write down the molecular structure and IUPAC names of the Isomer whose molecular structure is C₄H₁₀

(c) By naming reagent, stating conditions whenever possible using a balanced equation describe how Ethane could be converted into

1.     Ethane
2.  Chloromethane
3.      1,2,- dibromoethane

11.    Dilute Nitric acid is added to a green solid P.A blue solution R is formed and gas I Precipitate Lime with lime water is formed, the blue solution R is evaporated to dryness in a pyres test tube to give black solid M, brown fumes of gas W and colorless gas which relights a glowing splint was formed.

(a) Identify Substance P, R, I, M, W, and S 

(i) Dilute nitric acid and solid P

(ii) Formation of white precipitate with gas I and Lime water.

PRESENT’S OFFICE, REGIONAL ADMINISTRATION AND LOCAL GOVERNMENT

SECONDARY EXAMINATION SERIES

CHEMISTRY FORM FOUR

MID-TERM EXAMS – AUGUST – 2023

032/1 CHEMISTRY 1

TIME: 3:00 Hours YEAR. 2023

Instructions

1. This paper consists of sections A, B and C with a total of eleven (11) questions.
2. Answer all questions in section A and B and any two (2) question from section C
3. Section A carries sixteen (16) marks, section B carries fifty four (54) marks and section C carries thirty (30) marks.
4. All writing must be in blue or black ink except drawings which must be in pencil
5. All communication devices and any unauthorized materials are not allowed in the examination room
6. Write your Examination Number on every page of your answer sheet(s) provided.
7. The following constants may be used;

• Atomic masses H=1, C=12, K=39, O=16,S=32, Cl=35.5
• Avogadro’s constant = 6.02x10²³
• GMV at S.T.P = 22.4dm³
• 1Faraday =96500C
• 1Litre=1dm³=1000cm³

SECTION A: (16 Marks)

Answer all questions

1. For each of the following items (i) – (x) choose the correct answer among the given alternatives and write its letter besides the item number on the answer sheets provided.

1. A form one student saw the "flammable" sign on a box and made the following possible interpretations. Which one is the most correct?

1. The box contained firewood
2. The box contained papers
3. The box had radioactive materials
4. The box contained spirit used in lamps
5. The box contained health hazards

2. What should be done if the results obtained from an experiment do not support the hypothesis?

1. Experiment should be changed
2. Results should be left out
3. Ideas for further testing to find a solution should be given
4. Problem should be identified
5. Hypothesis should be accepted

3. The reaction between potassium metal and water is

Which of the following statement is true about this reaction?

1. Hydrogen is oxidized
2. potassium is reduced
3. Potassium is the reducing agent
4. Hydrogen is the reducing agent
5. Water is both oxidizing and reducing agent

4. How many molecules are there in 16.8litres of chlorine gas at STP?

1. 4.517 X10²³
2. 7.5 X10²³
3. 8.029 X10²³
4. 9.033X10²³
5. 6.75 X10²³

5. Ammonia is the basic gas that can obtained by reacting ammonium salt and calcium hydroxide. Which of the following can be used to dry ammonia during its preparation.

1. Concentrated sulphuric acid.
2. Calcium Chloride
3. Lime water
4. Calcium oxide.
5. Calcium Carbonate

6. Mr John treated water for domestic purpose, unfortunately the water remained hard on boiling and formed no leather with soap. Suggest the ions present in the water.

1. Ca²⁺ and HCO₃^-.
2. Ca²⁺ and CO₃ ^2-
3. Mg²⁺ and SO₃^2-
4. Mg²⁺ and HCO₃^-.
5. Mg²⁺ and SO₄^2-.

7. A mixture of 100cm3 of ethanol and 100cm3 of pure water can be separated by....

1. Solvent extraction
2. Simple distillation
3. Evaporation
4. Fractional distillation
5. Filtration

8. If Mr. Kashamba wants to electroplate his spoon with copper sulfate solution, he should arrange the electrode in the following way...

1. Spoon as Anode and copper cathode.
2. Spoon cathode and copper Anode
3. Spoon Anode and carbon cathode.
4. Spoon cathode and copper(II) sulphate anode
5. Carbon cathode and copper Anode

9. Which of the following sets represents isotopes of an element?

1. ¹⁶₇K , ⁷₈K and ¹⁸₉K
2. ¹⁶₇K , ¹⁶₉K and ¹⁶₈K
3.  and
4. ¹⁶₈K , ¹⁷₈K and ¹⁸₉K
5. ¹⁶₉K , ¹⁶₈K and ¹⁷₈K

10. Asha harvest unripe mangoes from her fruit garden, she then keep them till ripe and sell the mangoes. What changes occur for mangoes to turn ripe from unripe?

1. Physical change.
2. Chemical change.
3. Physical and chemical change
4. Neither physical nor chemical change.
5. Physical change and taste change

2. Match the uses of apparatus in list A with the respective element in list B by writing the letter of the correct response besides the item number in the answer sheet provided

SECTION B (54 Marks)

Answer all questions in this section

4, Juma was given two gas jars, one containing gas “X” and another one containing gas “Z” Gas “X” is used to prepare water gas in the laboratory and gas “Z” is used treating sewage plants

1. Identify the two gases
2. With reasons give the method used to collect gas “Z” in the laboratory
3. Give three uses of gas “X” in our daily life

4. 16.8 g of impure potassium hydroxide was dissolved in distilled water to make 100 ml. 20mls of this solution required 28mls of 0.07M sulphuric acid to react. Calculate;

1. Molarity of KOH
2. Mass concentration of pure KOH

5. (a) A form three student performed two different experiments

Experiment I; Students dissolved one tea spoon of sugar in cold water

Experiment II: Students dissolved one tea spoon of sugar in hot water

By using the concept of collision theory explain in which experiment the sugar dissolved more quickly?

(b)You are provided with the following equilibrium reaction

What happens to the production of ammonia if

1. Pressure increased
2. The equilibrium system is cooled
3. Hydrogen is removed
4. Nitrogen increased

6. Samwel bought all necessary building materials as he wanted to build modern and expensive house for his mother, four months later he found that almost all nails and iron sheets have been rusted, unfortunately he has no any extra money to buy the new nails and iron sheets. As a chemist student what will you advise Samwel (Give two points)

(b) Suppose you are in a bus travelling for annual holiday, a bus driver went to the petrol station to fill fuel but he forget to switch off the bus engine, this caused explosion hence the fire started.

As a form four student

1. How will you be able to use fire extinguisher to fight against fire?
2. Which type of fire extinguisher will be suitable for you to use? Give reason of your choice

7. (a)What are the four stages for extraction of moderate reactive metals

(b) In certain areas iron can be extracted through blast furnace which involve different temperatures such as1000⁰C, 750⁰C and 250⁰C in different stages

1. What is the chief ore in the extraction of iron
2. At what temperature reduction taking place?
3. What are the importance of coke, hot air and waste gases

(c).What are the two environmental effects caused by extraction of metals

8. During manufacturing of Sulphuric acid, Sulphur trioxide gas is dissolved in concentrated sulphuric acid instead of dissolving it directly in water

1. Explain why? And Write a balanced equation of dissolution of the gas in the acid
2. Write a balanced chemical equation for each of the following

1. Sulphuric acid act as an acid
2. Sulphuric acid act as an oxidizing agent.

SECTION C (30 Marks)

Answer only two questions from this section

9. Explain the term substitution reaction as applied in organic chemistry

(b)With the use of chemical tests differentiate between saturated hydrocarbons and unsaturated hydrocarbons.

(c). Write and name all isomers of pentane

10. The head master of Mtakuja secondary school advised an environmental master to use manure and fertilizers in order to improve the growth of trees and plant around the school .What are the significance of manure and fertilizers as per head masters advise.(Five points)

11. There are various environmental plans to be used in controlling the solid waste and soil pollution in Mbozi municipality. Advise accordingly to the effective plans to be taken in order to achieve such activities.( Five points)

PRESIDENT OFFICE REGIONAL ADMNISTRATION

AND LOCAL GOVERNMENT

SECONDARY EXAMINATION SERIES 

COMPETENCE BASED ASSEMENT

CHEMISTRY FORM FOUR 

TERMINAL EXAMS MAY – 2023 

032/1

CHEMISTRY

TIME: 3HOURS

INSTRUCTIONS

1. This paper consists of sections A, B and C with a total of eleven (11) questions.
2. Answer all questions in sections A and B and two (2) questions from section C.
3. Non-programmable calculators may be allowed.
4. Cellular phones and any unauthorized materials are not allowed in the examination room.
5. Write your Examination Number on every page of your answer sheet(s)
6. The following constants may be used: Atomic masses:

Atomic masses; H=1, O=16, Na=23, C=12, Cl=35.5, N=14, Zn=65, S=32,

  Ca=40, Fe=56, Cu=64, Al=27

GMV at s.t.p = 22.4dm³,   Avogadro’s number = 6.02 x 10²³

1Faraday = 96500 coulomb  1 litre = 1dm³=1000cm³

SECTION (16 MARKS)

1. For each of the items (i – x) choose the correct from the given alternatives and write it’s letter in the answer sheet provided

1. A substance which absorb water from the atmosphere and form a solution is called ....

1. Efflorescent
2. Hygroscopic
3. Deliquescent
4. Amphoteric

2. Technicians prefer to use blue flame in welding because

1. It is bright and non soot
2. It is light and non soot
3. It is very hot and non soot
4. It is not expensive

3. Chlorine ion Cl^- differ from chlorine atom because it has

1. More proton
2. Less proton
3. More electron
4. Less electrons

4.  This is a good example of

1. Neutralization reaction
2. Double decomposition reaction
3. Redox reaction
4. Synthesis reaction

5. The volume of 0.2M of H2SO4 acid required to neutralize completely 25.00cm³ of 0.05MKOH is...........

1. 0.626cm³
2. 3.125cm³
3. 12.500cm³
4. 6.315cm³

6. An electric current was passed through concentrated hydrochloric acid using carbon electrodes. The substance liberated at the anode was

1. Copper
2. Chlorine
3. Oxygen
4. Hydrogen

7. A good charcoal burns with................

1. Luminous flame
2. Non-luminous flame
3. Very low energy value
4. High production of gases

8. A covalent bond is formed when

1. Ammonia is formed
2. Potassium and Oxygen combine
3. A metal combines with nonmetal
4. An atom loses an electron.

9. The empirical formula of a certain compound is CH₃. Its molar mass is 30g/mol. What will be its molecular formula?

1. C₂H₆
2. CH₄
3. C₂H₈
4. C₂H₄

10. ........ is the general terms used to explain a mixture of different metals

1. Amphoteric
2. Allotrope
3. Isotope
4. Alloy

2. Match the item in LIST A with the correct response in LIST B

SECTION B (54 MARKS)

Answer all questions from this section

3. (a)Write balanced equation of

1. Sodium hydroxide react with Sulphuric acid
2. Calcium carbonate decomposed by heat

(b)(i)Wit aid of a balanced chemical equation name the products formed when nitrates of potassium and zinc decompose by heat

(ii)Suggest why nitrates of zinc and potassium behave differently on heating 

4. (a)(i)People suffering from heart burn usually use wood ashes for relief.

Mention characteristics which make the ashes to be used for heart burn relief

(ii)Give four compounds founds in the laboratory which show the same characteristic as ashes.

(b)How many ions are there in 6.82g of Al₂(SO₄)₃

5. A student tested four sample of water each 10cm³ from different areas at Malawi village by shaking by shaking with tree drops of soap solution. The experiment was repeated a second time by boiling each sample of water (10cm³) with three drops of soap solution. The observations were recorded as shown in the table below.

1. Which sample contains only temporary hard water? Give reason
2. Which sample contains permanent hard water? Give reason
3. Name the chemical substances that would be the causes of hardness in sample A
4. Write the chemical equation for removing hardness in

1. Sample A
2. Sample D

6. 5.3g of X₂CO₃ was dissolved in water to make 0.5 litres of a solution. 25cm³ of this solution required 50.0cm³ of 0.1MHCL for complete neutralization.

1. Write the balanced chemical equation for the reaction
2. Calculate the concentration of X₂CO₃ in mol/dm³
3. Calculate the relative molecular mass of X₂CO₃
4. Calculate the relative atomic mass of X
5. What is the name and symbol of element X

7. (a)Give two example in each of the following

1. Solid fuel
2. Gaseous fuel

(b)The reaction which produces methanol from carbon monoxide and hydrogen is represented by the equation 

The reaction is carried out at high pressure to give a better yield of methanol.

1. Explain why increase in pressure gives a better yield of methanol
2. The value of  is negative. What does this tell about the reaction
3. With reason state whether a high temperature or low temperature will give a better yield of methanol

8. Draw the well labeled diagram of laboratory preparation of Oxygen using the mixture of Potassium Chlorate and Manganese (iv) Oxide.

SECTION C (30 MARKS) 

Answer only two (2) questions from this section,

9. With the aid of the balanced chemical equations explain the processes that occur in the blast furnace during extraction of iron.
10. (a)Briefly explain the following observations with the help of equations

1. White anhydrous copper(II) sulphate changes its colour to blue when water is added
2. Vigorous reaction takes place when a small piece of sodium is placed in water.
3. Addition of zinc metal into a solution of copper (II) sulphate result into decolonization of the solution and deposition of a brown solid substance

(b)Define the following terms and give one example in each case

1. Weak acid
2. Acidic-salt

11. Potassium permanganate reacted with an acid A to produce gas B.

Then gas B is passed through water and finaly to concentrated

Sulphuric acid.

1. State;

1. The name of compound A and gas B
2. Two chemical tests of gas B
3. The method which is used to collect gas B. Give reason

2. Briefly explain as to why;

1. Gas B is passed through water and concentrated sulphuric acid
2. The preparation of gas B is always done in a fume chamber

3. Write the balanced chemical equation for the reaction between Potassium permanganate and acid A

PRESIDENT OFFICE REGIONAL  ADMINISTRATION AND LOCAL GOVERNMENT

SECONDARY EXAMINATION SERIES 

COMPETENCE BASED  ASSESSMENT

NEW EXAM FORMAT-2023

032/1 CHEMISTRY FORM FOUR 

MID-TERM EXAMS MARCH – 2023 

Time: 3:00 Hours

Instructions

1. This paper consists of section A, B and C with a total of thirteen (13) questions.
2. Answer all questions in this paper
3. Calculators, cellular phones and any unauthorized materials are not allowed in the examination room
4. Write your Examination Number on every page of your answer booklet(s)
5. The following constants may be used

• Atomic masses: H=1, C=12, O=16, N=14, Pb=108
• Avogadro’s number = 6.02 x 10²³
• GMV at s.t.p = 22.4 dm³
• 1 Faraday = 96,500 coulombs
• Standard pressure = 760 mm Hg
• Standard temperature = 273 K
• 1 litre = 1dm³ = 1000cm³

SECTION A (16 marks)

Answer All Questions

1. For each of items (i) – (x), Choose the correct answer from the alternatives and write its letter beside the item number in answer sheet provided

1. Mango Juice from Bakhresa was written, “Shake well before use” What does this mean?

1. Suspension
2. Solution
3. Solute
4. Emulsion
5. Solvent

2. Ammonia gas is collected by which method among the following

1. Downward Displacement of water
2. Upward delivery
3. Downward delivery
4. Upward Displacement of air
5. The elements are required by adult plant

3. What volume of hydrogen gas will be produced. When 1.3g of Zinc granules react completely with excess Dilute Sulphuric acid at S.T.P?

1. 223cm³
2. 130cm³
3. 440cm³
4. 220cm³
5. 448cm³

4. Which of the following substances should not be kept closely to the open bottle containing Carbon-dioxide

1. Dilute Nitric acid
2. Dilute Hydrochloric acid
3. Sodium hydroxide solution
4. Sodium Nitrate
5. Dilute Suphuric acid

5. When Nitrogen gas is formed covalently how many electrons are shared between nitrogen atom

1. 2
2. 3
3. 6
4. 5
5. 4

6. The reasons why white am hydrogen copper II sulphate tums blue when exposed in Atmosphere is that it

1. Absorbs water vapour
2. Reacts with Oxygen
3. Reacts with carbon dioxide
4. Becomes Dry
5. Release water to the atmosphere

7. Which action should be taken immediately after concentrated sulphuric acid is spilled on the skin

1. It should be rinsed off with large quantities of running water
2. It should be neutralized with concentrated NaOH
3. The affected area should be wrapped tightly and shown to a medical health provider
4. It should be neutralized with solid CaCO₃
5. It should be neutralized with concentrated KOH

8. The following particles forms the nucleus of an atom

1. Proton only
2. Neutron and Electron and neutron
3. Proton and Electron
4. Proton and neutron
5. Neutron and Electrons

9. What should be done if results Obtained from an experiment do not support the hypothesis

1. The results should be left out
2. A new problem should be identified
3. The experiment should be changed
4. Ideas for further testing to find a solution should be given
5. The hypothesis should be accepted

10. Water exists in three forms, solid, liquid and vapour which among the following are examples of liquid form of water?

1. Rain, Snow, hail
2. Dew, Rain, Ice
3. Mist, Steam, Cloud
4. Rain, Hail, Ice
5. Rain, Mist, Dew

2. Match the properties of element in List A with respective elements in List B by writing the letter of correct response besides item number in answer sheet provided

SECTION B (54 Marks)

Answer all questions in this section

3. (a) The modern Periodic table law is based on modification of Mendeleev Periodic law. Explain the two theories differ from each other.

(b) Comment on the following statement

1. Lithium has large size than Beryllium
2. Sodium is smaller than potassium

(c) Give four ions whose electron configuration resembles that of Neon

4. (a) Mr. Mwabashi asked student to prepare all requirements for extraction of sodium metal. Help them describe the use of each of the following

(i) Calcium Chloride (ii)Graphite rod (iii) Steel gauze

(b) Why is sodium collected upward in down cell?

(c) Write electrodes reaction is down cell during extraction of sodium

5. A solution contains 40.3g of substance XOH per liter 250.0cm³ of this solution required 30.0cm³ of 0.3M sulphuric acid for complete neutralization

1. Calculate the number of moles of XOH that reacted
2. Determine the relative atomic mass of X

6. (a) Differentiate alkanes from alkenes

(b) Study the flow chart below and answer questions that follow;

1. Identify A
2. State one Physical Property of B
3. Give a reason why D pollutes the environment
4. Write equation for formation of F
5. Describe an experiment which can be used to distinguish buteno from butanol.

7.  (a)A mass of 1.24g of a divalent metal was deposited when a current of 6A was passed through a solution of metal sulphate for 12minutes. Determine the relative atomic mass of the metal (1F = 96,500C)

(b)State two application of Electrolysis

8.(a) What is an alkali?

(b) Aqueous solution of 2M electronic acid and 2m nitric (v) acid were tested for electronic conductivity. Which solution is a better conductor of electricity? Explain

(c) Explain why it is not advisable to prepare a sample of carbon dioxide using barium carbonate and dilute Sulphuric (VI) acid

SECTION C (30 Marks)

Answer any two questions in this section

9. (a) What is Isomerism?

(b) Using illustration differentiate chain Isomerism from position Isomerism

(c) Alkenes are saturated, why alkenes are unsaturated explain

10. (a)Explain the following terms

1. Reversible reaction
2. Dynamic equilibrium

(b)The industrial Oxidation of sulphur dioxide is summarized as follows

2So_2(g) + O_2(g)  →  2SO_3(g) DH= -94.9 KJ/Mol

What will be the effect of each of the following on production of sulphur Trioxide?

1. Increase in moles of sulphur dioxide
2. Increase in pressure
3. Decrease of temperature
4. Decrease of moles of sulphur dioxide

(c)Briefly explain how each of the following factors affects the rate of a chemical reaction

1. Temperature
2. Pressure
3. Concentration
4. Catalyst
5. Surface area

(d) Give one good reason for the following

1. Fruits ripe faster during summer than during winter
2. Steel wire get rust faster than iron nails

11. (a)Using Iron filling, describe an experiment that can be conducted to show that Oxygen is present in air

(b)Element U has atomic number 12 while element V gas atomic number 16. How do the melting points of elements compare

(c) In haber process, nitrogen reacts with hydrogen according to the following equation;

3H_2(g) + N_2(g) → 2NH_3(g) DH= -92KJ/Mol

9. What would be the effect of adding catalyst to the position of equilibrium

2. Explain why it is not advisable to use a temperature higher than 773K in haber process

THE PRESIDENT’S OFFICE MINISTRY OF EDUCATION, REGIONAL ADMINISTRATION AND LOCAL GOVERNMENT

COMPETENCY BASED SECONDARY EXAMINATION SERIES

                                                                  CHEMISTRY   FORM FOUR

TIME: 2 HOURS                                                                                                          NOVEMBER 2022

INSTRUCTIONS:

1.     This paper consists of sections A, B and C

2.     Answer all questions in section A and B and only one (01) question from section C

3.     Cellular phones and all programmable calculators are not allowed in the examination room

4.     Write your examination Number on every page of your answer booklet(s)

5.     The following constants may be used

1 Faraday = 96500 coulombs

G.M.V at stp = 22.4dm ³

Avogadro's number = 6.02 x 10 ²³ particles per mole Atomic masses

H = 1, C = 12, O = 16, Na = 23, S = 32, cU = 64, Ag = 108, Zn = 65

SECTION A: (15 MARKS)

Answer all questions in this section

1. For each of the items (i) — (x), choose the most correct answer from among the given alternatives and write its letter in the space provided

(i)  The lead in a pencil is made of a mixture of graphite and clay. When the percentage of graphite is increased, the pencil moves across the paper move easily. Which  statement explain this observation?

A.    Graphite has high melting point

B.     Graphite is a lubricant

C.     Graphite is the form of carbon

D.    Graphite is a non — metal

E.     Graphite is a good conductor of electricity

(ii)  Which process is used to convert calcium carbonate into calcium oxide

A.    Electrolysis            

B.     Fractional distillation 

C.     Cracking

D.     Thermal decomposition

E.       Evaporation 

(iii)  One of the following substance is commonly used to determine the arrangement of metals in order or reactivity

A. Water  

B.     Salt  

C.    Acid

D. Base

E.  Non -metal

(iv)The hottest part of a non - luminous flame is the region of

A.     Green or blue zone          

B.     Purple or blue zone

C.    Colourless inner zone

D.   Thin outer zone

E.    Blue zone

(v)   The following are the properties of a good fuel except

A.     Average value of velocity or combustion

B.     High ignition point

C.     Highest energy value

D.     Environmental friends

E.      Less or no waste products

(vi)  A sodium atom (Na) and a sodium iron (Na+) have the same

A.     Atomic site 

B.    Electronic configuration

C. Physical properties

D. Physical properties 

E. Number of protons

 (vii)Factors in an experiment that remain unchanged throughout the experiment is known as

A.    Controlled variable           

B.     Dependent variable         

C.     Independent variable

D.    Uncontrolled variable

E.     Fixed factor

 (viii) Coal, methane and hydrogen are burned as fuel, which description of this process is correct?

(ix)Petroleum is a mixture of different hydrocarbons, which process is used to separate petroleum into groups of similar hydrocarbons?

A.     Combustion

B.      Cracking             

C.      Fractional distillation

D.      Reduction

E.      Isomerism

(x)   A car releases 5g of carbondioxide gas into air for each mile driven. The number of carbondioxide molecules released are

A.     1.0 x 10²³        

B.     6.8 x 10²³   

C.    6.3 x 10²³

D.   5.8 x 10²²

E. 6.8 x 10²²

2. Match the item in LIST A with a correct response in LIST B by writing the letter of tie correct response below the corresponding item in the table Given

SECTION B: (70 MARKS)

Answer all questions in this section

3.  (a) Element Q has 17 electron and 18 neutrons (i) What is the atomic number of element Q

 (ii) What is the mass number of element Q

(iii)  Write down the electronic configuration of element Q

(iv)  In which group and period in the periodic table does element Q occupy?

(b)Given the following ²⁰⁴J ²⁰⁸ K ²⁰⁷L and ^AM are isotopes of element H, whose abundances are 2%, 24%, 22% and X% respectively. Calculate the abundance X% and the mass number A of isotope M, given that the atomic mass of element H is 207.

4.  (a) State any three main physical properties of water and show the usefulness of each property.

(b)The following methods were used to soften 25cm ³ of the original sample of water. At the end of each experiment, the resultant product was treated with soap solution until lather was obtained

(i)     Which methods were most suitable for softening hard water?

(ii)    Which type of hardness was present in the sample provided? Explain 

(iii) Which substances caused the hardness in the sample water?

(iv) Why did distillation and filtration produce such different results?

5.  (a) Outline three reasons to explain why carbondioxide is used to extinguish fire

(b)A sample of mass 28.6g of hydrated sodium carbonate (Na2 C03. 101420) was heated such that water was entirely absorbed by 32g of anhydrous copper (Il) sulphate to form a blue compound of hydrated copper (Il) sulphate (CUS0₄ . XH₂0). Find the value of x in the copper (Il) sulphate

6.   (a) Complete and balance the following chemical equation.

 (b) Write down the condensed structural isomers of alcohol of molecular formula C₄H₁₀0

7.  (a) By using two examples in each case, categorize fuel according to their physical state

(b)  What is the simplest chemical formula of a compound formed when 36g of magnesium combine with 14g of nitrogen?

8.      (a) Complete the following table

 (b)   Using calcium oxide and carbon dioxide explain the meaning of

(i)     Acidic oxide (ii) Basic oxide

9.      A piece of marble chips (calcium carbonate) was placed in a beaker containing an excess of hydrochloric acid standing on a reading balance. The mass of the beaker and its contents were recorded after eve 2 minutes as shown in the diagram below

(a)    Why was there a loss of mass?     

(b)    Write the equation for the reaction above

(c)   State three (3) different ways in which reaction could have been more rapid 

(d)  Why did the mass remain constant after 10 minutes?

10.   (a) Nowadays the use of spatula which are made of iron is discouraged in the laboratory. Explain one reason for the scenario.

(b)  Write a chemical composition for the following fire extinguisher

(i)     Dry powder         (ii) Wet chemical

(c)   How can you prevent the following iron materials from rusting?

(i)            Gates

(ii)          Bicycle chain

(iii)          Iron sheets

11.   (a) How can a mixture of two or more miscible liquids be separated from one another?

(b)  Make a flow chart to show the separation of a mixture of common salt and sand

12.  Four  experiment were conducted using chemicals P, Q, L and M on different materials.

The results were given as indicated below. You are required to write the correct terminology which suits each of the results below and give precautions of handling the warning signs which goes with it.

(i)      When chemical P was poured on the wood it completely damage the surface of the wood

(ii)    When chemical Q was poured on the small fire, it found burst and turning a bigger fire

(iii)When chemical L was swallowed by a rat, the rat died immediately

(iv)When chemical M was exposed on air sudden blast accompanied with light occurred (b) Give one main importance of chemical warning signs

SECTION C: (15 MARKS)

13.  (a) State Faraday's first law of electrolysis

(b)The apparatus shown below was used in the experiment of electroplating a key with silver. The electrolyte used is silver nitrate and an electric current of 15A was passed in the electrolyte for two and half hours. Study it carefully and answer the questions that follows;

(i) Name the process taking place on key as either oxidation or reduction

(ii) With the current of 15A, what mass of silver was deposited on the key? 

(iii) Name the gas formed at the anode

(iv)  Name the acid formed as a result of electrolyzing silver nitrate

 (v)  What volume of the named gas in (iii) above was collected in this experiment?

14.  (a)  Eutrophication is excessive growth of aquatic plant and algae in water bodies (i) Give two causes of eutrophication

(ii) Explain the effect of eutrophication. (Give two points)

(b)Explain how industrial workers can be protected against harmful effect of the chemicals. (Give three points)

THE PRESIDENT’S OFFICE MINISTRY OF EDUCATION, REGIONAL ADMINISTRATION AND LOCAL GOVERNMENT

COMPETENCY BASED SECONDARY EXAMINATION SERIES

CHEMISTRY

FORM FOUR- SEPT 2022

CODE 032/1

INSTRUCTIONS

1. This paper consists of sections A, B and C with a total of fourteen (14) questions
2. Answer all questions in sections A and B and one (1) question from section C
3. Sections A and C carry fifteen (15 ) marks each and section B carries seventy (70) marks
4. Cellular phones and any unauthorized materials are not allowed in the examination room
5. Write your Examination Number on every page of your answer booklet(s)
6. The following constants may be used

Atomic masses H=1, C=12 , N=14, O=16 , Cl=35.5 , CU=64 , P=15, Fe=56

Avogadro’s number =6.02 x 1023.

GMV at s.t.p= 22.4 dm3.

1 Faraday = 96,500 coulombs.

Standard pressure =760 mm Hg.

Standard temperature =273 K.

1 litre = 1 dm3 =1000 cm3.

SECTION A (15 Marks)

Answer all questions in this section

1. For each of the items (i) - (x), choose the correct answer from among the given alternatives and write its letter beside the item number in the answer booklet provided.

1. A metal nitrate which will not give a metal oxide on heating is:

1. Calcium nitrate 
2. Silver nitrate 
3. Lead nitrate
4. Copper nitrate
5. Zinc nitrate

2. What number of faradays of electricity is required to deposit 4g of calcium from molten calcium chloride?

1. 0.1 
2. 0.2 
3. 0.4 
4. 0.3 
5. 0.7

3. When methane undergoes substitution reaction with excess chlorine. What is the final product?

1. Chloromethane
2. Dichloromethane
3. Trichloromethane
4. Tetracloromethane
5. Monochloromethane

4. The reason why white anhydrous copper (II) Sulphate turns blue when exposed in Atmosphere is that it

1. Absorbs water vapour
2. Reacts with oxygen
3. Reacts with carbon dioxide
4. Become dry
5. Release water to the Atmosphere

5. Which action should be taken immediately after concentrated sulphuric acid is spilled on the skin?

1. It should be rinsed off with large quantities of running water.
2. It should be neutralized with concentrated NaOH
3. The affected area should be wrapped tightly and shown to a medical health provider
4. It should be Neutralize with solid CaCO₃
5. It should be neutralized with concentrated KOH

6. The molarity of 5.3g in 100ml of Na₂CO₃ solution is

1. 0.2M
2. 0.5M
3. 0.05M
4. 0.005M
5. 0.01M

7.                     The reaction between hydrogen and Iodine is represented by H_2(g) + I_2(g) 2HI_(g) H=-xKJ/mol The reaction is

1. Endothermic reaction
2. Neutralization reaction
3. Displacement reaction
4. Exothermic reaction
5. Decomposition reaction

8.                   One of the following apparatus is used to measure fixed volume of liquid

1. Burette
2. Pipette
3. Conical flask
4. Measuring cylinder
5. Volumetric flask

9. A substance which absorb water from the atmosphere and form a solution is called

1. Efflorescent 
2. hygroscopic 
3. deliquescent
4. amphoteric
5. salt

10. AgNO_3(aq) + NaCl_(aq) → AgCl_(s) + NaNo_3(aq). This a good example of

1. Neutralization reaction 
2. double decomposion reaction 
3. Redox reaction 
4. synthesis reaction
5. decomposition.

2. Match the properties of element in list A with the respective element in List B by writing the letter of the correct response besides the item number in answer sheet provided.

3. (a) The Modem periodic law is based on modification of Mendeleev periodic law. Explain how the two theories differ from each other.

(b) Comment on the following statement

(i) Lithium has large size than Beryllium

(ii) Sodium is smaller than potassium

(c) Give any four ions whose electronic configuration resemble to that of Neon. (07 Marks)

4. a) How many chlorine molecules are in 20cm³ of chlorine gas at s.t.p.

b) Calculate number of ions present in 5g of copper (II) Nitrate

5. (a) (i) People suffering from heart burn usually use wood ashes for relief. Mention chacteritics which makes the ashes to be used for heart burn relief.

(ii) Give four compounds found in the laboratory which show the same characteristic as ashes. 

(b) How many ions are there in 6.82g of Al₂(SO₄)₃

6. 5.3g of X₂CO₃ was dissolved in water to make 0.5 litre of a solution. 25cm³ 0f this solution required 50.0cm³ of 0.1M HCl for complete neutralization.

a) Write the balanced chemical equation for the reaction

b) Calculate the concentration of X₂CO₃ in mol/dm³

c) Calculate the relative molecular mass of X₂CO₃

d) Calculate the relative atomic mass of X

e) What is the name and symbol of element X

7. (a) A gaseous compound consists of 86% Carbon and 14% Hydrogen by mass. At S.T.P, 3.2dm³ of the compound had mass of 6g.

(i) Calculate its molecular formula

(ii)Give the IUPAC name of the compound

(b) Most of the apparatus in the laboratory are made up of glass materials. Support this statement by giving ant two (2) reasons. (07 Marks)

8. Element R having atomic number 20 combines with element S having atomic number 17 to form a certain compound

a) Write the formula of the compound and state the type of bond formed in the compound

b) Give any three properties of the compound formed in 7(a) above

9. a) Muumini is a student from Katosani secondary school, she is not able to State Le Chatellier’s principle, Help her.

b) In the industrial preparation of Sulphur trioxide mr Atieno yo established equilibrium between Sulphur dioxide and oxygen gas as follows:

2SO_2(g) + O_2(g)   2SO_3(g)∆H= - 94.9KJ/mol.

i. How would you adjust temperature and pressure to maximize the proportion of the product at equilibrium? 

ii. Why is it unfavorable to work with very high pressure and very low temperature in the contact process? 

iii. What catalyst is used to speed up the rate of formation of Sulphur trioxide before attaining the equilibrium?

10. a) Mr Mapulishi tasked to prepare all requirements for extraction of sodium.Describe the use of each of the following during extraction of Sodium

i. Calcium Chloride ii. Graphite anode

iii. Steel gauze

b) .Why sodium is collected by upwards in the downs cell

c) Write electrodes reaction in downs cell during extraction of Sodium

11. Mr Kalubandika wanted to know some chemistry pertaining concepts. Help Mr Kalubandika to answer the following conceptual questions.

a) In which other areas do we find the warning signs out of laboratory (give four point)

b) Explain how measurements of volume differ when using measuring cylinder and burette

c) It is recommend that laboratory apparatus should be properly washed or wiped after use, explain the significance for this when

i. Measuring volume of liquids

ii. Measuring mass of substance

12. (a) Give the meaning of the following terms

(i) Soil pH (ii) Liming

(b) (i) Explain why sulphur and its compounds are removed from the fuel before they are burned

(ii) By using a reaction equation explain how propane differs from propene

13. (a) Outline any three uses of carbon dioxide gas in animals and plants

(b) Complete the following reactions

(i) CH₂=CH₂ + O₂

(ii) CaC₂ + 2H₂O 

(iii)CH₄ +Cl₂  

(iv) C₂H₅OH +O₂  

14. In q certain chemical plant that deals with the production of hydrogen gas, a certain chemist passes an electric current in series through copper (II) Sulphate and sulphuric acid solutions. In both electrolytes, inert electrodes were used. If 8400cm3 of hydrogen at S.T.P were produced for several hours, what volume of oxygen gas would also be produced? What mass of copper was produced?

 14. Using a well labelled diagram, explain how sulphur is extracted using the Frasch process

THE PRESIDENT’S OFFICE

MINISTRY OF EDUCATION, REGIONAL ADMINISTRATION AND LOCAL GOVERNMENT

COMPETENCE BASED SECONDARY EXAMINATION SERIES

CHEMISTRY MID TERM EXAMINATION

FORM FOUR-MARCH/APRIL-2022

Time: 3Hours

Instructions.

1. This paper consists of section A, B and C with a total of 14 questions
2. Answer all questions in section A and B and ONE (1) question from section C.
3. Section A and C carries 15 marks, while section B 70 marks
4. Cellular phones and any unauthorized materials are not allowed in the examination room.
5. Non programmable calculators may be used.
6. Write your number on every page of your answer booklet.
7. Where necessary the following constants may be used;

Atomic masses; H=1, C=12, N=14,O=16, Na=23, S,=32, Ca =40, Cl =35.5, Cu=64, Zn=65.

Avogadro’s number = 6.02 x 10²³

GMV at s.t.p = 22.4dm³

1 faraday = 96,500 coulombs.

Standard temperature = 273K

Standard pressure = 760mmHg.

1 Litre = 1 dm³ = 1000cm³

 SECTION A (15 Marks)

 Answer All questions in this section.

1. The method of collecting hydrogen chloride gas in a class experiment is known as:

1.              Downward displacement of water
2.               Downward displacement of air
3.               Upward displacement of air
4.              Fountain
5.               Condensation

2. The only metal which does not react with dilute hydrochloric acid is:-

1.              Magnesium
2.               Copper
3.               Zinc
4.              Sodium
5.               calcium

3. Which among the following equations correctly shows the reaction between chlorine gas and water?

1.              C l_2(g) + H₂0₍₁₎→CI_2(g)

B          2C1_2(g) + 2H₂0₍₁₎→ 4C1^-1_(aq) + 0_2(g) + 2H_2(s)

3.               Cl_2(g) + H₂0₍₁₎→HCl + HOCI(aq)
4.              2Cl_2(g) + 2H₂0(_I) →2H0C1 +H_2(g)
5.               2C12(g)+ 3H₂0₀₎ → C1_{2 (.0} + 2H₃0⁺

4. A gas which when exposed to air forms white fumes is likely to be:

1.              Nitrogen
2.               Chlorine
3.               Ammonia
4.              Hydrogen chloride
5.               Sulphur.

v. Which is not true about hydrogen chloride?

1.              It supports combustion
2.               It is a very soluble gas
3.               It forms white fumes with ammonia
4.              It is acidic in nature
5.               When exposed to air forms white fumes

6. Sea water contains various salts. Which salt is present in the largest proportion?

A.      Magnesium sulphate 

B.      Sodium chloride

C.       Calcium sulphate 

D.      Magnesium chloride

7. Study the chemical equations below: which can remove temporary and permanent hardness?

a.       Ca(HCO3)2(aq) → CaCO3(g) + H2O(l) + CO2(g)

b.      Ca(HO)2(aq)  + Ca(HCO3)2(aq) → CaCO3(g) + 2H2O(l) 

c.       Ca2+(aq) + CO2-(aq)  → CaCO3(g) 

d.      Ca2+(aq)  + Na2Z(aq) → 2Na+(aq) + CaZ(g)

8. Hard water which is softened just by boiling contains dissolved; 

A.       Calcium carbonate 

B.       Calcium chloride 

C.       Sodium carbonate 

D.      Magnesium sulphate 

E.       Calcium hydrogen carbonate 

9. Which of the above equations (vii) removes temporary hardness of water only? 

A.      a and b

B.      b and c 

C.      c and d

D.      d and a.

10. Which set of compounds when in water cause hardness easily removed by boiling addition of Na₂CO₃ or use of ion exchange?

A.      Ca(HCO₃)₂,  Mg(HCO₃)₂

B.      CaCl₂,  MgSO₄

C.       Fe(NO₃), Ca(NO₃)₂

D.      mgCl₂, FeCl₂

2. Match the physical processes represented by arrows (i) - (v) in List A with the corresponding terms in List B by writing the letter of the correct response beside the item number in the answer booklet provided.

3. Figure 1 below represents the laboratory preparation of hydrogen chloride gas.

(a) Name the parts labelled A, B, C and D.

(b) (i) Do you think the gas can be collected over water? Give reasons for your answer.

2.                      Explain the test for the gas.
3.                      What is the function of C?
4.                      Name the method used to collect the gas.
5.                      Write a balanced chemical equation for the reaction taking place during the preparation of hydrogen chloride gas.

(c) Write chemical equations for the reaction between:

(i) Ammonia gas and hydrogen chloride.

(ii) Hydrogen chloride gas and water.

4. Write equation for reaction between

5.                      Chlorine and Magnesium
6.                      Chlorine and phosphorous
7.                      Chlorine and copper
8.                      Chlorine and hydrogen sulphate

5. Explain what happens when a stream of Hydrogen chloride gas is passed over

1.                      Ammonia  gas
2.                      Iron II solution.

6. Study the diagram below and answer the questions that follow

The apparatus above are used to prepare chlorine

1.          State substance

Y

X

P

2.                      What is the use of conc. Sulphuric acid?
3.                      State the use of p.
4.                      Write equation for reaction occurring at the flask.
5.                      How can you show that  test tube used for collection of chlorine is full?
6.                      Name the method of collection
7.                      Give two uses of chlorine
8.                      State  2 compounds of chlorine that pollute the environment.

7.      Write down the chemical equations used when softening water of the 

(a)  Temporary hardness through (i) boiling water (one question)   (ii) use of chemicals (two equations)

(b)  Permanent hardness through (i) use of chemicals (one equation) (ii) iron exchange (one equation)

8.      Define the following terms;

(e)  Soft water 

(f)    Hard water 

(g)  Permanent hardness of water  (h) Temporary hardness of water 

9.      a) What is the hardness of water?

b)  Briefly explain types of hard of water.

c)   State the causes of hardness of water for each type mention in (b) above.

d)  Explain how you would remove the hardness of water according to its type.

e)  Give three (3) advantages and three (3) disadvantages of the hard water.

10.   Balance the following equations: 

  (i)Ca + H₃PO₄→ Ca₃(PO₄)₂ + H₂

2.                      Cu + HNO3 → Cu (NO3 )₂ + NO2 +H20
3.                      SnCi₂+FeC1₃→SnC1₄+FeCI

11.     Give the name of the types of reaction represented by each of the following chemical equations.

1.                      C₃H_8(g) +50,₍₀₎→ 3CO2 + 4H₂0₍₁₎
2.                      2Pb (N 0₃),₍,₎→2Pb0₍,₎ + 4NO2 +0_2(g)

(iii)Zn(s)+CuS0_4(aq) —>ZnSO_4(aq) +CU(S)

12.     Complete the following equations and determine the type of chemical reaction involved in each case.

(i) Zn(s)+ H₂SO_4(aq)→

(i) AgN 03_(aq) + NaCl_(aq)→

(iii) N_2(g) + H_2(g) →