FORM FOUR CHEMISTRY MIDTERM-2 EXAMS

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
  1. 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
  1. 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
  1. 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
  1. 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
  1. 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 SO32-
  4. Mg2+ and HCO3-.
  5. Mg2+ and SO42-.
  1. 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
  1. 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
  1. Which of the following sets represents isotopes of an element?
  1. 167K , 78K and 189K
  2. 167K , 169K and 168K
  3. image and image
  4. 168K , 178K and 189K
  5. 169K , 168K and 178K
  1. 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

LIST A

LIST B

i. Holding , heating and estimating the volume of liquids

ii. Holding substances that are being weighed or observed

iii. Holding chemicals and heating small portions of chemicals of liquid or solid form

iv. Adding small volume of liquids reagents to an exact point during experiment

v. Holding and measuring liquid during experiment

vi. Measuring mass of chemicals in the laboratory
  1. Measuring syringes
  2. Electronic balance
  3. Filter funnel
  4. Test tube
  5. Beaker
  6. Flasks
  7. Watch glass
  8. Thistle funnel

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)

FORM FOUR CHEMISTRY EXAM SERIES 163  

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FORM FOUR CHEMISTRY EXAM SERIES 163  

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
  1. 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
  1. When methane undergoes substitution reaction with excess chlorine. What is the final product?
  1. Chloromethane
  2. Dichloromethane
  3. Trichloromethane
  4. Tetracloromethane
  5. Monochloromethane
  1. 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
  1. 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
  1. 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
  1.                     The reaction between hydrogen and Iodine is represented by H2(g) + I2(g)https://myfiles.space/user_files/30996_4958b541bbe404eb/1659864474_chemistry-dar/1659864474_chemistry-dar-1.png 2HI(g) https://myfiles.space/user_files/30996_4958b541bbe404eb/1659864474_chemistry-dar/1659864474_chemistry-dar-2.pngH=-xKJ/mol The reaction is
  1. Endothermic reaction
  2. Neutralization reaction
  3. Displacement reaction
  4. Exothermic reaction
  5. Decomposition reaction
  1.                   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
  1. A substance which absorb water from the atmosphere and form a solution is called
  1. Efflorescent 
  2. hygroscopic 
  3. deliquescent
  4. amphoteric
  5. salt
  1. AgNO3(aq) + NaCl(aq) → AgCl(s) + NaNo3(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.

LIST A

LIST B

(i) A black solid element which burns with reddish glow giving off colorless gas which is slightly acidic

(ii) Silvery white metal which burns with golden yellow flame giving an oxide which is basic in nature

(iii)A yellow element in color which burns with blue flame giving colorless gas which is strong acidic in nature

(iv) A shinning white strip metal burns with dazzling white flame giving an oxide which is slightly basic in nature

(v) A silvery white metal which burns with brick red giving off oxide which is white solid

 
  1. Calcium 
  2. Iron
  3. Sodium
  4. Zinc
  5. Magnesium
  6. Carbon
  7. Sulphur

 

 

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:

2SO2(g) + O2(g)  image 2SO3(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 + O2image

(ii) CaC2 + 2H2O image

(iii)CH4 +Cl2  image

(iv) C2H5OH +O2  image

 

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?

 

FORM FOUR CHEMISTRY EXAM SERIES 119  

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FORM FOUR CHEMISTRY EXAM SERIES 119  

 

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

COMPETENCY BASED SECONDARY EXAMINATION SERIES

CHEMISTRY -SEPT 2022

FORM FOUR

 CODE 032/1 

CHEMISTRY 1

TIME:3HOURS                                                                                                         SEPT    2022

 

INSTRUCTIONS

  1. This paper consists section A, B and C with a total of fourteen questions.
  2.  
  3. Cellular phones and any unauthorized materials are allowed in the examination room.
  4. Non – programable calculator may be used in the examination room.
  5. Write your examination number on every page of your answer booklet(S).
  6. The following constant may be used.

Atomic masses H = 1, O = 16, S = 32, Zn = 65, Fe = 56, Cu = 64, Ca = 40.

Avogadro’s number = 6.02  1023

GMV at s.t.p = 22.4dm3

1 Faraday = 96500 coulombs

1Litre = 1dm3 = 1000cm3

 

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. The element with a proton number 17, has similar chemical properties to the element with the proton number _______
  1. 7      (b) 9         (c) 16        (d) 19        (e) 17.5

 

  1. Which statement about catalyst is correct?
  1. Are used in industry to reduce energy cost
  2. Are used up during a reaction
  3. Increase the activation energy of chemical reactions
  4. Transition metals are not good as catalyst
  5. Used to form products of reaction

 

 

  1. A man suffering from excess of acid in the stomach has no indigestion tablets. Which substance could he take to lower his acidity?
  1. Asprin, PH 6          (b)Bicarbonate of soda, PH8

( c)Lemon juice, PH 5  (d)Salt water, PH 7

                      ( e)Orange juice PH 4

 

  1. Excess zinc carbonate reacts with dilute hydrochloric acid according to the equation shown below.

ZnCO3(s) + 2HCl(aq)               →        ZnCl2(aq) + CO2(g) + H2O(l)

What volume of carbon dioxide gas is produced at S.T.Pto form 0.1 mole of the acid?

  1. 1.2dm3      (b) 2.4dm3    (c) 12dm3  (d) 24dm3   (e) 4.5fm3

 

  1. A pupil dissolved some ammonium nitrate crystals in water as shown below.

Before                                                           After

 

                       What type of reaction took place above?

  1.             Endothermic reaction     (b)Exothermic reaction

( c)Neutralization                (d)Reduction reaction (e)Resolution reaction

 

  1.                Which of the following is not a commercial use of hydrogen gas?
  1.             Manufacture of ammonia (b)Used to support lives of living things

 (c)Manufacture of margarine (d)Formation of water  (e)As rocket fuel

  1.             A student read the following statements on an article about how carbon dioxide is formed.
  1.                From the fermentation of glucose
  2.                When calcium carbonate reacts with dilute hydrochloric acid
  3.                When methane burns in a limited supply of oxygen

Which of these statements are correct?

  1. 1, 2 and 3   (b) 2 and 3 only   (c) 1 and 3 only

  (d)1 and 2 only  (e) 3 and 2 only

 

  1.           An acid differs from a base in that an acid.
  1.             Turns a red litmus paper (b)Has a PH value above 7

 (c)Has a sour taste               (d)Turns a blue litmus paper red

                        (e)Does not react with base

 

  1.                Methane is a green house gas. Which process releases methane into the air?
  1.             Combustion
  2.             Decay of vegetable matter
  3.             Volcanic activity
  4.             Photosynthesis
  5.             Decantation

 

  1.                  The following role is played by organic matter in the soil.
  1.             Improving water infiltration of the soil
  2.             Accelerating break down of organic matter
  3.             Reserving nutrients thus providing soil fertility
  4.             Converting nitrogen into nitrate
  5.             Providing a room for organic materials such as nylon

 

  1.                                                                                       Match the description in list A with the corresponding response in list B by writing the letter of the correct response besides the item number in the answer booklet/sheet.

LIST A

LIST B
  1.                                                                                      A gas prepared in the laboratory by isolation from the air.
  2.                                                                                   A non – metal this is a good conductor of heat and electricity.
  3.                                                                                 Extracted by frasch process.
  4.                                                                                 It is only alkaline gas
  5.                                                                                    Forms white precipitate with aqueous silver nitrate solution.
  1.                                                                                     Ammonia
  2.                                                                                     Sulphur dioxide
  3.                                                                                     Carbon
  4.                                                                                     Nitrogen
  5.                                                                                      Sulphur
  6.                                                                                      Chlorine
  7.                                                                                     Hydrogen chloride.

 

 

 

 

SECTION B (70 Marks)

Answer all questions from this section

  1.                   (a) As a chemist what factors would you consider in selecting a good fuel? (5points)
  1.                Why it is not advisable to sleep inside a house which is not well ventilated with a burning wooden charcoal? Support your answer with chemical equation. (7 marks)

 

  1.                   (a) (i)What is oxidation number of iron in iron (III) chloride?

(ii) In the following reaction state the substance which is reducing agenda and oxidizing agent.

 

H2 (g) +CuO(S) → Cu (g) +H2O (l)

(b) Classify the following reaction into oxidation and reduction reaction.

  1.                  Fe3+(aq)+ e                 →            Fe2+(aq)

(ii) Fe2+(aq)+ e                →             Fe3+(aq)

(iii) S(s) + O2(g)                    →                      SO2(g)

(iv) N2(g) + 3H2(g)              →                    2NH3(g)    (7 marks)

  1.                   A spillage of 15.5kg of sulphuric acid results from an accident of a road tanker. Slaked lime is used to neutralize the acid according to the equation below.

H2SO4 (aq) + Ca(OH)2(aq)         →   CaSO4(aq) + H2O(l)

  1.                Balance the equation above
  2.                Determine the molar mass of Ca(OH)2
  3.                Use the balanced equation to determine the mass of calcium sulphate formed during the neutrazation of the spilt acid.
  4.                Calcium hydroxide is base, which ion present in the compound is responsible for its basic properties?(7marks).

 

  1.                   (a) Most metals are not found as pure elements in the earth’s crust, and iron is one such metal. Iron is exctracted from its ore in a blast fumace.
  1.                              Name two other raw materals added to the blast fumace other than haematite.
  2.                            Write abalanced chemical equation for the reduction of the iron ore to the metal.

(b) State three conditions necessary for rusting to occur.(7marks)

 

 

  1.                   (a) Use the following list of elements to answer the equations below iron, lethium, mercury, oxygen, potassium, sulphur.
  1.                              Is used as catalyst in the manufacture of ammonia in the habor process.
  2.                            Is lower than sodium in the reactivty series.
  3.                         Is a non – metallic solid, whose atoms contain only six valency electrons.
  4.                          Is in period 4 of the periodic table.
  5.                            Forms an oxide which is amphoteric.

(b) Explain how the knowledge of chemistry is applied in the following field.

(i) Pharmacy       (ii) agriculture (7marks)

 

  1.                   (a) Why it is important to treat and purify water? Five points.

(b) Give out the role of the following chemicals in water treatment and purification.

  1.                              Chlorine
  2.                            Aluminiun sulphate(7 marks)

 

  1.                   (a) The choice of indicator during titration depends on the properties of the reactants. State the suitable indicator in the following titration.
  1.                              Ethanoic acid + ammonium solution
  2.                            Sodium hydroxide + ethanoic acid
  3.                         Potassium hydroxide + hydrochloric acid
  4.                          Hydrochloric acid + ammonia solution

(b) In volumetric analysis not all reactions are suitable for titration. Give out three conditions necessary for titration. (7 marks)

 

 

  1.              (a) The amount of subsatances liberated at electrodes during electrolysis depends on different factors.  State three factors according to the statement above.

(b) 0.4 faradays of electricity were passed through solutions of copper (II) sulpahete and dilute sulphuric acid. Calculate the volume of hydrogen gas produced at S.T.P.(7amrks)

 

  1.              (a) Give an account for the following.
  1.                              Anhydrous copper (II) sulphate becomes coloured when exposed to the air for a long time.
  2.                            Carbon dioxide gas can be collacted by down ward delvery method.
  3.                         Concentrated sulphuric acid is not used for drying hydrogen sulphide gas.
  4.                          Sodium metal is kept in paraffin oil.

(b) Write all possible isomers of (C5H8).(7marks)

 

 

  1.              (a) Study the following equation carefully and answer the questions below.

  1.                              Explain three factors which would maximize the yield of ammonia.
  2.                            How equilibrium state can be attained.

(b) Draw the warning sign that should be put to the container caring the following chemicals.

(i) Concentrated sulphuric acid.

(ii) Zinc sulphate crystals (7marks)

 

SECTION C (15Marks)

Answer only one question from this section

  1.              Many countries this year have experienced shortage of rainfall that has resulted to poor yield of crops and death of animal due to lack of water and pastures. Scientists have advised that the problem is due to air pollution in many countries in the world. Explain what might happen in the future to the world if the present trend of polluting the air is not controlled and checked. (Six points)

 

  1.              With the aid of diagram describe how sulphur is extracted from its deposit.

 

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FORM FOUR CHEMISTRY EXAM SERIES 113  

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FORM FOUR CHEMISTRY EXAM SERIES 113  

THE UNITED REPUBLIC OF TANZANIA

PRESIDENT’S OFFICE

REGIONAL ADMINISTRATION AND LOCAL GOVERNMENT

FORM FOUR MID TERM EXAMINATION-2021

CHEMISTRY 

Time 3:00 HrsAUG, 2021

Instructions 

  1. This paper consists of section A, B & c with a total of fourteen (14) questions.
  2. Answer all questions in section A & B and one (1) question from section C.
  3. 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, O=16, S=32, Ca=40, Zn=65, Cl=35.5, Na=23, C=12, Ag=108

Avogadro’s number = 6.02 x 1023

GMV at s.t.p = 22.4dm3

1 faraday = 96,500 coulombs

1 litre = 1dm3 = 1000cm3

SECTION A (15Marks)

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. What number of faradays of electricity is required to deposit 4g of calcium from molten calcium chloride?
  1. 0.1      B.  0.2        C. 0.4       D. 0.3        E. 0.7
  1. When methane undergoes substitution reaction with excess chlorine. What is the final product?
  1. Chloromethane
  2. Dichloromethane
  3. Trichloromethane
  4. Tetracloromethane
  5. Monochloromethane
  1. Which name is given to the uniform mixture of metals?
  1. Compounds     B. Alloys     C. Ores     D. Salts     E. Mixtures
  1. The reaction between iodine and hydrogen is represented by the following equations

I 2(g) + H 2(g)                            2HI (g)

The reaction is:-

  1. An endothermic reaction
  2. A displacement reaction
  3. A neutralization reaction
  4. A thermal decomposition reaction
  5. An exothermic reaction
  1.                                  The electronic configuration of this element  Cl- is
  1. 2:8:7    B. 2:8:8    C. 2:8:8:1      D. 2:8:8:2      E. 2:8:6
  1. Glucose dissolves in water to form a uniform mixture.
  1. water is solution, glucose is solvent and the product is solute
  2. water is solute, glucose is solvent and the product is solution      
  3. water is solvent, glucose is solute and the product is solution
  4. water and glucose forms immiscible mixture
  5. water and glucose form emulsion
  1. 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
  1. In order to produce the greatest amount of hydrogen in a short time, one gram of magnesiumribbon should react with
  1. 10cm3 of 0.5M Sulphuric acid
  2. 40cm3 of 0.5M acetic acid solution
  3. 40cm3 of 0.5 Sulphuric acid solution
  4. 20cm3 of 1M Sulphuric acid solution
  5. 20cm3 of 1M acetic acid solution
  1. Which of the following substances represent a group of acid oxides?
  1. Carbon dioxide, carbon monoxide and Sulphur dioxide.
  2. Sulphur trioxide, Nitrogen dioxide and Nitrogen monoxide
  3. Carbon dioxide, Sulphur dioxide and dinitrogen oxide
  4. Sulphur trioxide, carbon dioxide and Nitrogen dioxide
  5. Carbon monoxide, nitrogen oxide and sulphur dioxide.
  1. Which action should be taken immediately after concentrated sulphuric acid is spilled onthe 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
  1. Match the items in List A with the response in List B by writing the letter of the corresponding responses beside the item number.

LIST A

LIST B
  1. Biogas
  2. Biomass
  3. Natural gas
  4. Producer gas
  5. Water gas
  1. Industrial gas which is a mixture of hydrogen and carbon monoxide
  2. Non- renewable gaseous fuel
  3. Industrial gases fuel which is a mixture of nitrogen gas, hydrogen and carbon monoxide
  4. Gases fuel derived from decomposition of biological waste
  5. Renewable source of energy
  6. Water gas and ammonia
  7.  Ammonia and butane

SECTION B (70Marks)

Answer all questions in this section

  1.                                                                                                                                                                                                                                                                                                                        (a)
  1.                                                                                                                                                                                                                                                                                                      What is laboratory?
  2.                                                                                                                                                                                                                                                                                                      Name two main compound used in preparation oxygen gas in laboratory
  3.                                                                                                                                                                                                                                                                                                      Why hydrogen gas is collected by downward displacement method?

(b) Complete and balance the following chemical reaction 

  1.                                                                                                                                                                                                                                                                                                      NaOH(ag) + HCl(ag)→
  2.                                                                                                                                                                                                                                                                                                      NH4Cl(ag) +NaOH(ag)→
  3.                                                                                                                                                                                                                                                                                                      Ca(OH)2(ag) +H2SO4(ag)→
  4.                                                                                                                                                                                                                                                                                                      Mg(s)  +HNO3(ag)→
  1.                                                                                                                                                                                                                                                                                                                        Element R having atomic number 20 combines with element S having atomic number 17 to form a certain compound
  1. Write the formula of the compound and state the type of bond formed in the compound
  2. Give any three properties of the compound formed in 7(a) above
  1.                                                                                                                                                                                                                                                                                                                         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

  1.                                                                                                                                                                                                                                                                                                                        a) State LeChatellier’s principle.

b) In the industrial preparation of Sulphur trioxide equilibrium is established between Sulphurdioxide and oxygen gas as follows:

2SO2(g) + O2(g)⇋2SO3(g)∆H= - 94.9KJ/mol.

  1. How would you adjust temperature and pressure to maximize the proportion of the productat equilibrium?
  2. Why is it unfavorable to work with very high pressure and very low temperature in thecontact process?
  3. What catalyst is used to speed up the rate of formation of Sulphur trioxide beforeattaining the equilibrium?
  1.                                                                                                                                                                                                                                                                                                                        a) What is molecular formula?
  1. You are provided with a compound composed of 22.2% Zinc, 11.6% Sulphur, 22.3% oxygen and the rest percentage is water of crystallization. Calculate the molecular formula of the compound if its molecular mass is 283.
  1.                                                                                                                                                                                                                                                                                                                        In one titration experiment 25cm3 of hydrated sodium carbonate Na2CO3.XH2O were titrated against 20cm3 of 0.25M hydrochloric acid. The solution of sodium carbonate was made by dissolving 7.15g of the compound in 250cm3 of distilled water.

Use the above data to answer the following questions

  1. Write down a balanced equation to represent the acid base reaction
  2. i. Find the morality of the anhydrated sodium carbonate

ii. Calculate the value of X in the hydrated sodium carbonate.

  1.                                                                                                                                                                                                                                                                                                                        a)Describe the use of each of the following during extraction of Sodium
  1. Calcium Chloride
  2. Graphite anode    
  3. Steel gauze

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

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

  1.                                                                                                                                                                                                                                                                                                                   a) State Faraday’s Laws of Electrolysis
  1. Dilute silver nitrate solution was decomposed by the passage of electric current through it. What mass of silver and what volume of oxygen (Measured at s.t.p) would be liberated in electrolysis by 9650 coulombs of Electricity?
  1.                                                                                                                                                                                                                                                                                                                   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 

  1. Measuring volume of liquids 
  2. Measuring mass of substance  
  1.                                                                                                                                                                                                                                                                                                                   a) State three main physical properties of water and show the usefulness of each property 

  b) State four industrial application of electrolysis   

SECTION C (15 MARKS)

Answer one (1) question in this section

  1.                                                                                                                                                                                                                                                                                                                   a) How can you tell water is polluted? Give two ways
  1. We have coal at Kiwira in Mbeya region. Authorities in the government have allowed use of coal for domestic and industrial purpose. What warming can you raise concerning likely effects? Give five points
  1.                                                                                                                                                                                                                                                                                                                    a) Define the following terms
  1. functional group
  2. homologous series
  3. isomerism

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

      c)By naming the reagents, stating the conditions whenever possible using a balances equation describe how ethane could be converted into

  1. Ethane  
  2. Chloroethane
  3. 1,2-dibromoethane  
  4. Ethanol

1

FORM FOUR CHEMISTRY EXAM SERIES 68  

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FORM FOUR CHEMISTRY EXAM SERIES 68  

THE PRESIDENT’S OFFICE

MINISTRY OF EDUCATION, REGIONAL ADMINISTRATION AND LOCAL GOVERNMENT

COMPETENCE BASED SECONDARY EXAMINATION SERIES

CHEMISTRY MID TERM EXAMINATION

FORM FOUR-AUG/SEPT 2021

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

(i) 1.4 g of potassium hydroxide is dissolved in water to form 250 cm3 of solution. What is the molarity of this solution?

  1.  0.01 M
  2.  0.1 M
  3.  1.4 M
  4.  5.6 M
  5.  6.0 M

(ii) In the blast furnace carbon monoxide is prepared by passing carbon dioxide over a red­hot coke. Carbon dioxide is

  1.  an accelerator
  2.  an oxidizing agent
  3.  a reducing agent
  4.  a catalyst
  5.  oxidized.


(iii) Copper can be separated from a mixture of zinc and copper by adding to the mixture

  1.  concentrated H2SO4
  2.  dilute H2SO 4
  3.  aqueous solution of ZnSO4
  4.  concentrated HNO3
  5.  a catalyst.

(iv)  65.25 g sample of CuSO4.5H2O (M = 249.7) was dissolved in water to make 0.800 L of solution. What volume of this solution must be diluted with water to make 1.00 L of 0.100 M CuSO4?

  1.   3.27 ml
  2. 383 ml
  3. 209 ml
  4. 65.25 ml
  5. 306 ml.

 (v)  Which action should be taken immediately after concentrated sulphuric acid spilled on the skin?

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

(vi)  The only metal which does not react with dilute hydrochloric acid is

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

(vii)  10 cm3 of 0.4 M sodium hydroxide are added to 40 cm3 of 0.2 M hydrochloric acid. The resulting mixture will be

  1. Neutral
  2. Alkaline
  3. Dilute
  4. Acidic
  5. Amphoteric

(viii)  The ionic equation when aqueous ammonium chloride reacts with sodium hydroxide solution is represented as:

  1. 2NH+4(aq) + 2Cl-(aq)à 2NH3(g) + Cl2(g) + H2(g)
  2. NH+4(aq) + OH-(aq) à NH3(g) + H2O(l)
  3. Na+(aq) + Cl-(aq) à NaCl(g)
  4. H+(aq) + OH-(aq) à H2O(l)
  5. 2NH+4(aq) + 2Cl-(aq) à 2NH3(g) + 2HCl(g).


(ix) The apparatus suitable for measuring specific volumes of liquids is called?

  1. Burette
  2. Volmetric flask
  3. Pipette
  4. Measuring cylinder
  5. Graduated beaker

(x) The property of metal to be drawn into wires is called?

  1. Conductivity
  2. Malleability
  3. Ductility
  4. Decorating
  5. Expansion.

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.

LIST A

LIST B
  1. Saturated hydrocarbon
  2. Sweet smelling compound
  3. Decolorizes bromine in sunlight
  4. Making of soap
  5. Same molecular formula but different structural formular
  1. Monomer
  2. Isomer
  3. Ethene
  4. Ester
  5. Methane
  6. Saponification
  7. Esterification
  8. All carbon bonds are used in bonding


SECTION B (70 Marks)

Answer all questions in this section.

3. (a) How many chlorine molecules are in 20 cm of chlorine gas at s.t.p? 


   (b)Calculate the number of ions present in 5 g of copper II nitrate. (7 marks)


4. A solution contains 40.3g of substance XOH per litre .250.0cm3of this solution required 30.0cm3 of 0.3M sulphuric(VI)acid for complete neutralisation.

(a) Calculate the number of moles of XOH that reacted. 

(b) Determine the relative atomic mass of X. 

5. Sulphur(IV) oxide is prepared in the laboratory using the set-up in Figure 3.

Study it and answer the questions that follow.

https://www.advance-africa.com/images/sulphuric.png

(a) Identify substance F. (1 mark)

(b) Write an equation for the reaction that takes place in the flask. (1 mark)


(c) State the purpose of liquid G. (1 mark)

6. (a) A mass of 1.24g of a divalent metal was deposited when a current of 6A was passed through a solution of a metal sulphate for 12 minutes.Determine the relative atomic mass of the metal( Faraday = 96,500 C mol-1(3 mark)

(b)  State two application s of electrolysis.



7. In the Haber process, nitrogen reacts with hydrogen according to the following equation.

3H2(g) + N2(g)→ 2NH3(g) ; AH = -92 kJ/ mol

(a) What would be the effect of adding a catalyst on the position of the equilibrium? (1 mark)


(b) Explain why it is not advisable to use temperatures higher than 773 K in the Haber process. (2 marks)

8. You are provided with solid potassium hydrogen carbonate. Describe how a solid sample of potassium nitrate can be prepared.

9. Study the set-up in Figure 6 and answer the questions that follow.

(a) Name the substance that was collected in tube P. (1 mark)

(b) Write an equation for the reaction which occurs in tube Q in the first few minutes of the experiment. (1 mark)


(c) Give a suitable conclusion for the experiment in the set-up. (1 mark)


10.W is a colourless aqueous solution with the following properties:

I It turns blue litmus paper red.

II On addition of cleaned magnesium ribbon, it gives off a gas that burns with a pop sound.

III On addition of powered sodium carbonate, it gives off a gas which forms a precipitate with calcium hydroxide solution.

IV When warmed with copper(II) oxide powder, a blue solution is obtained but no gas is given of

V On addition of aqueous barium chloride, a white precipitate is obtained.

(a) (i) State what properties (I) and (III) indicate about the nature of W. ( I mark)

(ii) Give the identity of W. (l mark)

(iii) Name the colourless solution formed in (II) and (III). (2 marks)

(iv) Write an ionic equation for the reaction indicated in (V). ( I mark)

11.   (a) 20 cm3 of a solution containing 7 g dm-3 of sodium hydroxide were exactly neutralized by 25 cm3 of 0.10 M hydrochloric acid. Calculate the concentration of sodium hydroxide in moles per dm3.

(b)  (i) Write the reaction equations involved in the industrial manufacturing of sulphuric acid starting with sulphur dioxide in the contact process.

 (ii) Explain why sulphur trioxide is not dissolved directly in water to obtain sulphuric acid in contact process.

12.  (a) In the blast furnace, iron ore can be reduced using coke at a temperature of about 1300°C.

(i) Write an equation for the exothermic reaction that causes this high temperature.

(ii) State how carbon monoxide is formed.

(iii) Write a word equation for the formation of slag.

12. (b) Consider elements with atomic number 1, 11, 12 and 17.

(i) What are the types of oxides formed by elements with atomic number 11 and 12?

(ii)  Write an equation which represents a reaction between the element with atomic number 1 and 17.

(iii) Write a balanced chemical equation between the oxide of the element with atomic number 11 and aqueous solution of the compound formed in 4 (a) (ii).


SECTION C (15 Marks)

Answer one (1) question in this section.

13. Explain five methods to prevent terrestrial pollution.

14.  (a) A current of 0.5 A were made to flow through silver voltameter for 30 minutes. Calculate the mass of silver deposited and the equivalent weight of silver.

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

(i)  Addition reaction.

(ii)Elimination reaction.

FORM FOUR CHEMISTRY EXAM SERIES 58  

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FORM FOUR CHEMISTRY EXAM SERIES 58  


THE PRESIDENT'S OFFICE

MINISTRY OF REGIONAL GOVERNMENT AND LOCAL GOVERNMENT

PRE-NATIONAL  EXAMINATION SERIES-1

CHEMISTRY  FORM-4

2020

TIME: 3:00 HRS

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. Cellular phones and any unauthorised 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, O- 16, N- 14, S = 32, Zn - 65, Cl -35.5, cu - 64.

Avogadros number= 6.02 x 1023 image

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 cm 3.

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.

(i) "Water is referred to as the universal solvent". What does this mean? 

  1. Water is neither acidic nor basic as compared to other liquids.
  2. Water exists in three states of matter than any other liquids.
  3. Water dissolves both organic and inorganic solutes. 
  4. Water is used more domestically than any other liquids.
  5. Water dissolves more substances than any other known liquids.

 (ii) A current of 0.2 A was passed through an electrolyte for 16 minutes and 40 seconds. What is the quantity of electricity produced in coulombs?

  1.  2000 C  
  2. 1000 C 
  3.  200 C 
  4.  0.20 C 
  5.  7686 C.


(iii) Substance X liberates chlorine gas from acidified potassium chloride. The behaviour of X is described as:

  1.  an oxidising agent    
  2.  an oxidising and reducing agent
  3.  catalyst   
  4.  a reducing agent
  5.  bleaching agent.

(iv) Which carbonate is the most stable to heat?

  1.  Calcium carbonate   
  2.  Copper (II) carbonate
  3.  Lead (II) carbonate 
  4.  Zinc carbonate 
  5. .Iron (II) carbonate.

(v)  Aluminium does not react with water and does not corrode much in air because

  1.  it is below hydrogen in the reactivity series
  2.  it forms a stable carbonate which prevents reactions
  3.  the metal is covered with a protective coating of an oxide 
  4.  aluminium ions have positive charges
  5.  it is very stable.

 

(vi) Which of the following compounds does NOT belong to the alkenes homologous series?

  1.  C2H4 
  2.  C3H6  
  3.  C4H 8 
  4.  C5H10 
  5.  C6H 14.

(vii) Which of the following is NOT among the composition of air?

  1. Noble gases 
  2. Carbon dioxide 
  3. Nitrogen 
  4. Hydrogen 
  5. Water vapour. 

(viii)   Chlorine ion, Cl- differs from chlorine atom because it has       

  1.   more protons. 
  2.  less protons. 
  3.  more electrons. 
  4.  less electrons. 
  5.  more neutrons.

(ix) Which of the following pairs of compounds can be used in the preparation of calcium sulphate?

  1. Calcium carbonate and sodium sulphate
  2. Calcium chloride and ammonium sulphate
  3. Calcium hydroxide and barium sulphate 
  4. Calcium nitrate and lead (II) sulphate 
  5. Calcium chloride and barium sulphate. 

(x)  Which of the following solutions is the most concentrated?

  1. 50 g of calcium carbonate in 100 cm3 of water
  2. 60 g of sodium chloride in 200 cm3 of water
  3. 65 g of potassium nitrate in 100 cm3 of water
  4. 120 g of potassium sulphate in 200 cm3 of water
  5. 50 g of sodium hydroxide in 200 cm3 of water.

 

2.  Match the items in List A which the responses in List B by writing the letter of the correct response beside the item number in the answer booklet provided.

LIST A

LIST B
  1. Its nitrate decomposes to the metal, nitrogen dioxide and oxygen. 
  2. Its chloride is used as a drying agent for most gases.
  3. Its carbonate is used to remove hardness of water.
  4. Has maximum valency of five.
  5. Burn with a lilac color flame.
  1.  Potassium
  2.  Copper
  3.  Argon
  4.  Calcium
  5.  Sulphur
  6.  Chlorine
  7.  Carbon
  8.  Boron
  9.  Silicon
  10.  Zinc
  11.  Beryllium
  12.  Neon
  13.  Hydrogen
  14.  Helium
  15.  Sodium
  16.  Lead
  17.  Iodine
  18.  Manganese 
  19.  Phosphorus
  20.  Silver 

SECTION B (70 Marks)

Answer all questions in this section.

3. (a) (i) State Avogadro’s law of gaseous volume.

(ii) Find the volume of oxygen gas required to burn completely 1 dm3 of methane. CH4 + 2O  2(g) ? CO  2 + 2H  2O. 

(iii) What is the volume of carbon dioxide formed in the reaction at (ii) (4 marks)

(b) Define the following terms:

(i) Mole

(ii) Molecular weight (2 marks)

 

4. (a) Ammonia gas can be prepared by heating an ammonium salt with an alkali

(i) Name the most common pair of reagents suitable for this reaction.

(ii) Write the equation for the reaction. (4 marks)

(b) Ammonia is very soluble in water and less dense than air. How does each of the properties determine the way in which ammonia is collected in a gas jar? 

5. (a) Differentiate empirical formula from molecular formula

(b) Calculate the empirical formula for a compound with the following composition: lead 8.32 g, sulphur 1.28 g, oxygen 2.56 g (relative atomic wt of lead = 207, sulphur = 32, oxygen = 16)

6. (a) Classify the following reactions into oxidation and reduction reactions.

(i)  S( s) + O 2( g) ? SO 2( g)

(ii) N2( g) + 3H 2( g) ? 2NH 3( g)

(iii) Fe2+ (aq) ­ e ­  ? Fe3+ (aq)

(iv) Fe3+ (aq) ­ e  ­  ? Fe2+ (aq)  (4 marks)

(b) What is the oxidation number of iron in iron (III) chloride? (3 marks)

7.(a) Explain the meaning of the following:

(i) Malleable

(ii) Ductile

(iii) Brittle 

(b) Give an account of the following

(i) Anhydrous copper (II) sulphate becomes coloured when exposed to the air for a long time.

(ii) Carbon dioxide can be collected by the downward delivery method.

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

(iv) Sodium metal is kept in paraffin oil. 

8. (a) (i) What is the first step to take when you want to identify the contents of a given salt containing one anion and one cation?

(ii) In a solution of water, identify a solute and a solvent. Justify your answer. 

(b) Sodium is a solid while chlorine is a gas at room temperature although they are in the same period in the periodic table. What is the cause of this difference?

9. (a) (i) Name three gases which should not be produced in order to prevent the destruction of ozone layer. 

 (ii) List and explain three effects of ozone layer depletion.

(b) Lack of safe water for domestic and industrial uses is a serious problem in most of Tanzanian towns. The major cause of this problem is pollution in the water sources. Slate three methods that could make water from a pond or a well be safe for drinking.

10. (a) (i) Name the products formed when nitrates of potassium and zinc decompose by heat. 

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

(b) Mention two uses of sodium nitrate.

11. (a) Which ways are the fossil fuels detrimental to the environment? Give four points. 

(b)  Briefly explain how biogas is produced by using domestic waste.

12. (a) (i)  Define isomerism.

(ii) Draw and name two structural formulae of the isomers of C4H8.

(b) Carbon dioxide can be prepared by adding an acid to calcium carbonate.

(i) Using a named acid, write a balanced chemical equation for the reaction. (ii) Name all the products formed in (b) (i)

SECTION C (15 Marks)

Answer one (1) question from this section.

13. Describe the cause, two effects and measures to be undertaken in order to prevent/reduce the amounts of acid rain.

14. 0.48g of a metal, M was placed in a test tube and hot copper (II) sulphate solution was added to it and stirred until the reaction stopped. The metal (M) displaced copper from copper (II) sulphate solution. Copper was filtered, washed with water, dried at 1000 C  and the mass found to be 1.27g. Given that, the balanced chemical reaction that occurred is M (s)  + CuSO  4(aq)  imageMSO  4(aq)  + Cu  (s) 

(a) Calculate;

  1. The number of moles of copper that were formed and the number of moles of M that were used in the reaction.
  2. The relative atomic mass of M and hence identify metal M.

(b) State the appearance of the metal formed (Cu).

(c) With ionic equations, explain why the reaction can be considered to involve both oxidation and reduction.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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