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 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

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

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

CHEMISTRY- MOCK- EXAMINATION-MAY

FORM FOUR

Time 3:00 Hours MAY 2020 

INSTRUCTIONS.

1. This paper consist of three sections A, B and C
2. Answer all questions in section A and B and one question in section C.
3. The following constants may be used; H= 1. C=12. O= 16, Ag = 108, Cu =63.5

1 Litre = 1dm³ = 1000cm³

G.M.V at STP = 22.4dm³

Avogadro’s constant = 6.02 x 10 ²³ particles.

 SECTION A: 15 MARKS.

1. MULTIPLE CHOICE QUESTIONS.

 (i) Which among the given list of metals arranged in order of decreasing reactivity with steam from left to right is correct?

1.  Calcium, Magnesium, Silver, Copper.
2.  Calcium, Magnesium, Zinc Copper
3.  Copper, Zinc, Magnesium, Calcium
4.  Calcium, Zinc, Magnesium Copper.
5.  Calcium, Magnesium, Zinc, Copper

(ii) A study current of 4A was passed through an aqueous solution of Copper Sulphate for 1800seconds. Mass of Copper deposited will be: 

1.  63.5
2.  31.75g
3.  1.185g
4.  2.37g
5.  11.8g.

(iii) Which of the following statement is true? Avogadro’s Constant is the number of?

1.  Element in one mole of solid substance
2.  Atoms in one mole of any gas at S.T.P
3.  Atoms in one mole of a metal
4.  Elements needed to liberate one gram of univalent metal
5.  Elements released when one mole of an element is discharged at the anode.

(iv) An organic compound of structural formula …………………………… belongs to homologous series of:

1.  Isomers
2.  Allotropes
3.  Molecules
4.  Radicals
5.  Isotopes.

(v) The atmosphere effect of burning fuel such as wood and petrol oils is to:

1.  Reduce Oxygen
2.  Produce clouds
3.  Add carbon dioxide
4.  Increase water vapour
5.  Produce energy.

(vi) Elements loose or gains electrons to form.

1.  Isotopes
2.  Radicals
3.  Molecules
4.  Ions
5.  Allotropes.

(vii) Which of the following groups of organic compounds is prepared by dehydration of corresponding alcohol?

1.  Alkynes
2.  Alkenes
3.  Alkanes
4.  Esters
5.  Carboxylic acid

(viii) Which of the following is most ductile?

1.  Alluminium
2.  Silver
3.  Copper
4.  Tin
5.  Mercury.

(ix) The same current passing through solution of the same concentration of silver nitrate and Copper Sulphate liberates 0.23g of Silver (equivalent weight = 108). The weight of Copper that will be liberated, (equivalent weight 31.8) is?

1.  318g
2.  0.0677g
3.  0.23g
4.  0.033g
5.  3.18g

(x) In a blast furnace carbon monoxide is prepared by passing carbon dioxide over red – hot coke. Carbon dioxide is: 

1.  An accelerator
2.  An Oxidizing agent
3.  A Reducing agent
4.  A catalyst
5.  Oxidized.

2. Match the items in List A with responses in List B by writing the letter of correct response beside the item number in List A.

SECTION B:

3. (a) Give the reason for use of carbon dioxide

(i) As a fire extinguisher  ( ½ marks)

(ii) As a refrigerant  ( ½ marks)

(iii) In baking.  ( ½ marks)

(b) Explain what will happen when carbon monoxide reacts with:

(i) Oxygen  ( 1 marks)

(ii) Concentrated sodium hydroxide  ( 1 marks)

(iii) Copper II Oxide.  ( 1 marks)

 (c) (i) Outline steps in preparation of charcoal  ( 1¹/₂ marks)

(ii) Mention two chemical properties of charcoal.  (1 marks)

4. (a) Give two example for each or the following

(i) Strong acid  ( 1 marks)

(ii) Strong alkali  ( 1 marks)

 (b) Identify the products formed when strong acid react with 

(i) CuO_(s)  ( 1¹/₂ marks)

(ii) NaOH_(aq)  ( 1¹/₂ marks)

 (c) Explain the meaning of the following and give two examples in each case.

(i) PH scale of an acid  ( 1 marks)

(ii) Organic Acid.  ( 1 marks)

5. (a) Describe the effect of:

(i) Strongly heating a piece of marble in Bunsen burner flame.  ( 1¹/₂ marks)

(ii) Moistening the residue (1) above with water.  ( 1¹/₂ marks)

 (b) 

(i) For what reason is slaked lime added to soil in gardening? ( 2 marks)

(ii) Why is concentrated sulphuric acid used as drying agent? ( 2 marks)

6. The preparation of ammonia M the laboratory is done by heating a mixture of ammonium chloride and sodium hydroxide.

(a)

(i) Write a balanced equation for the reaction  ( 1¹/₂ marks)

(ii) Use equations to show how ammonia reacts with hydrogen chloride gas and healed Copper II Oxide. ( 1¹/₂ marks)

 (b) 

(i) State two uses of ammonia  ( 1marks)

(ii) Name the catalyst used in preparation of ammonia  ( 1marks)

(c) Explain each of the following reactions giving observation and equations.

(i) Aqueous ammonia is added to iron (III) Chloride, little by little until in excess. ( 1marks)

(ii) Sodium nitrate is strongly heated. ( 1 marks)

7. 

a) Draw a well labeled diagram of non – luminous flame of Bunsen burner. 1 marks)

b) Explain the meaning of:

(i) Malleable  ( ¹/₂ marks)

(ii) Ductile  ( ¹/₂ marks)

(iii) Brittle   ( 1 marks)

 (c) Give an account for the following:

(i) Anhydrous Copper II Sulphate becomes coloured when exposed to air for long time.

 ( 1 marks)

(ii) Carbon dioxide can be collected by down ward delivery method. ( 1 marks)

(iii) Concentrated sulphuric acid is not used for drying hydrogen sulphide. ( 1 marks)

(iv) Sodium metal is kept in paraffin oil. ( 1 marks)

8. 

a) Element A, B, C and D have atomic numbers 6, 8, 17 and 20 respectively. Write electronic structure of those elements ( 2 marks)

b) Write down the formulae of simplest compounds you would expect when;

(i) A and B combine chemically  ( ¹/₂ marks)

(ii) C and D combine chemically  ( ¹/₂ marks)

 c) 

(i) What types of bonding you would expect between compounds above? ( 1 marks)

(ii) List three differences between bonds you have identified above ( 3 marks)

9. (a)

(i) Name the product formed when nitrate of potassium and Zinc decompose by heating.

( 1¹/₂ marks)

(ii) Suggest why the nitrate of Zinc and potassium behave differently when heating.

 ( 1¹/₂ marks)

 (b) Mention four uses of sodium nitrate. ( 4 marks)

10. 

a) Giving four reasons, explain why people who use hard water can expect higher costs than people who use soft water. ( 3marks)

b) Suggest one method for separation of each of the following

(i) Iodine and sand   ( 1marks)

(ii) Green solution form leaves   ( 1marks)

(iii) Alcohol and water   ( 1marks)

(iv) Iron fallings and powdered calcium carbonate.   ( 1marks)

11. (a) A current of 0.5A were made to flow through silver voltmeter for 30 minutes. Calculate mass of silver deposited and equivalent weight of silver. ( 2marks)

 (b) Explain the following reactions giving one example in each.

(i) Addition reaction   ( 2marks)

(ii) Elimination reaction.   ( 2marks)

12. (a) With an aid of chemical equations, explain the following terms,

(i) Esterification reaction   ( 1marks)

(ii) Substitution reaction   ( 1marks)

(iiii) Double decomposition reaction   ( 1marks)

(b) Give a reason why alluminium is used in;

(i) Cooking Utensils   ( 1marks)

(ii) Overhead Electricals   ( 1marks)

(iii) Window Frames   ( 1marks)

SECTION C:

Answer Only one Question.

12. Describe the two causes, two effects and measures to be undertaken in order to prevent/reduce the amount of acidic rain. (15 marks)

13. Consider the following.

 Use Le Chaletires Principle to describe how the rate of production of D can be altered. (15 marks)