THE UNITED REPUBLIC OF TANZANIA NATIONAL EXAMINATIONS COUNCIL OF TANZANIA CERTIFICATE OF SECONDARY EDUCATION EXAMINATION 

032/1   CHEMISTRY 1

(For Both School and Private Candidates)

 Time: 3 Hours                                              Thursday, 08^th November 2018 a.m.

Instructions

1. This paper consists of sections 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,  0=16,    N = 14,  Cu = 64,   Pb = 108. vogadros 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 (20 Marks) 

Answer all questions in this section.

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

 (i) Which of the following is an agricultural chemical products made by the application of chemistry?

1. Drugs           
2. Pesticides        
3. Clothes 
4. Yeasts 
5. Cement.

 (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) In the following equilibrium equation, 2S0_2(g) +O_2(g)  2S0₃ The forward reaction is exothermic. Which change would increase the production of sulphur trioxide at equilibrium?

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

(viii) When a burning fuel produces blue color it means there is

1. adequate supply of oxygen with production of soot.
2. inadequate supply of oxygen without production of soot. 
3. inadequate supply of oxygen with production of soot.
4.  adequate supply of oxygen with production of less heat.
5.  adequate supply of oxygen with production of more heat.

(ix)  Which of the following equations represents the combustion of methane with the products collected at 120^oC?

1.  CH4(l) +2O2(g) →CO2(g) + 2H2O(l)
2.  CH4(g) +2O2(l) →CO2(s) + 2H2O(l)
3.  CH4(g) +2O2(g) →CO2(g) + 2H2O(g)
4.  CH4(l) +2O2(l) →CO2(l) + 2H2O(g)
5.  CH4(l) +2O2(g) →CO2(g) + 2H2O(g)

   (x) Which of these can be reduced when heated with carbon?

1.  Aluminium  
2. Calcium carbonate
3. Iron (III) oxide 
4. Magnesium oxide 
5.  Sodium oxide.

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

SECTION B (54 Marks) 

Answer all questions in this section.

3.(a) Define the following terms: 

1. Neutralization.
2. Unsaturated solution.
3. Thermal decomposition.

(b) (i) List two advantages of liming.

       (ii) State two roles of climate in the soil formation.

4.   (a) Copper obtained from copper pyrites (CuFeS2) is impure for electrical wiring and has to be purified by electrolysis.

(i) Name the electrolyte and the electrodes used during electrolysis. 

(ii) Write the observations that can be made during the electrolysis.

(b) The following flow diagram shows the stages in the contact process

 (i)     Give the names of element A, catalyst B and an acid C.

 (ii)  Write  a balanced chemical equation for the formation of sulphur trioxide in stage 2

5. (a) Suggest one method of separating each of the following:

(i)             Green solution from leaves. 

(ii)      Alcohol from water.

 (b)   Elements K, L, M and N have atomic numbers 6, 8, 9 and 20 respectively. Classify each element into its respective period and group.

6.  (a) Give one example in each of the following:

 (i) Alkali earth metals.

(ii)  Noblegases .

(iii) Transition elements.

(b) Write the names of the following processes of changing matter from one state to another.

(i) Gas to liquid. 

(ii) Ga s to solid. 

(iii) Solid t o gas .

7 (a) Define the following:

   ( i ) Mole .

 ( i i ) Molarmass .

(b) 112 dm³ of oxygen gas was collected at s.t.p when a sample of lead nitrate was completely decomposed by heat. Calculate the volume of nitrogen dioxide gas produced.

8. (a) Distinguish manures from fertilizers. Give an example in each case.

(b)  The following equation shows the reaction between hydrogen and iodine gas to form hydrogen iodide gas,H_2(g)  + I_2(g)  ↔ 2HI (g) ∆H= -800Kj/mol.                   Giving a reason, explain what would happen to the position of equilibrium if 

(i) temperature is lowered.

(ii) hydrogen iodide gas is pumped into the system.

9.  (a) (i) Name the products formed when hydrogen sulphide react with chlorine gas. (ii) Mention two uses of hydrochloric acid.

(b) (i) Name the compound which causes temporary hardness of water and the compound which causes permanent hardness of water.

(ii) Write one balanced chemical equation in each case to show how to remove temporary and permanent hardness of water.

10. (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).

 11 . ( a ) With the aid of a chemical equation, describe how you would prepare pure solid sodium chloride by the action of an acid and a base.

  (b) (i) Why petroleum and coal are non-renewable sources of energy?

(ii) Give three alternatives to non-renewable sources of energy. 

SECTION C (26 Marks) 

Answer all questions in this section.

 12. Three moles of nitrogen gas combine with five moles of hydrogen gas to form ammonium gas by Haber process.

1.  Which reactant is present in smaller amount?
2.  Calculate the grams of the reactant left in the container.
3.  How many moles of NH₃ are produced?
4.  How many litres of NH3 are produced at STP?

13. In Tanzania, soil conservation is very important for Industrial Materials production. Explain six methods that are used to manage loss of plant nutrients from the soil.

THE UNITED REPUBLIC OF TANZANIA NATIONAL EXAMINATIONS COUNCIL CERTIFICATE OF SECONDARY EDUCATION EXAMINATION

032/1              CHEMISTRY 1

(For Both School and Private Candidates)

Time: 3 Hours     Thursday, 02^ndNovember 2017 a.m.

 Instructions

1.  This paper consists of sections A, B and C with a total of thirteen (13) questions.
2. Answer all questions in this paper.
3. Calculators, 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,   C = 12,    O = 16,    S = 32,    Ca = 40,    Fe = 56,    Cu = 64,    Zn = 65.

   Avogadro’s number = 6.02 x 103 ²³.

GMV at s.t.p. = 22.4 dm .

1 Faraday = 96,500 coulombs.

Standard pressure = 760 mm Hg.

Standard temperature = 273 K. 1 litre = 1 dm³ = 1000 cm³. 

           SECTION A (20 Marks) 

Answer all questions in this section.

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

 (i)  Which of the following sets of elements is arranged in order of increasing electronegativity?

1.  Chlorine, fluorine, nitrogen, oxygen, carbon
2.  Fluorine, chlorine, oxygen, nitrogen, carbon
3.  Carbon, nitrogen, oxygen, chlorine, fluorine 
4. Nitrogen, oxygen, carbon, fluorine, chlorine
5.  Fluorine, nitrogen, oxygen, chlorine, carbon.

(ii) Which type of a fire is associated with electrical equipment.

1.  Class E 
2.  Class C 
3.  Class F 
4. Class B 
5.  Class A.

(iii)   Which of the following is the electronic configuration of an element Y found in period 3 and group II of the periodic table?

1.  2:8 
2.  2:8:2    
3.  2:6
4. 2:8:8:2   
5. 2:8:4 

(iv) Technicians prefer to use blue flame in welding because 

1. it is bright and non-sooty 
2. it is light and non-sooty.
3.  it is very hot and large.
4. it is very hot and non-sooty.
5.  it is not expensive.

(v) Which method could be used to separate the products in the following equation?

1.  Chromatography
2. Crystallisation 
3. Distillation 
4. Filtration 
5. Condensation.

(vi) The 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.

(vii)  Which of the following compounds does NOT belong to the alkane homologous series?

1.    C2H 4    
2.  CH4    
3. C4H 10     
4.  C3H 8              
5. C5H 12.

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

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

(ix)   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.

(x) 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. 

2. Match the items in LIST A with the responses in LISTB by writing the letter of the correct response beside the item number in the answer booklet provided.

     SECTION B (54 Marks)

Answer all questions in this section.

3. (a) Define the following terms:

1. Soil.
2. Leaching.
3. Denitrification.

(b)   With the aid of a chemical equation, briefly explain how

1. temporary hardness of water can be removed by boiling.
2. permanent hardness of water can be removed by chemical means.

4. (a) State four steps employed in the extraction of moderate reactive metals.

(b) Write balanced chemical equations to show how chlorine reacts with the following:

1. water.
2. aqueous iron (II) chloride solution.
3. hydrogen sulphide.

5. (a) Copper can be obtained from the ore, copper pyrites (CuFeS2). The ore is heated in a limited amount of air giving the following reaction:

 4CuFeS2 + 11O 2 → 4Cu + 2Fe 2 O 3 + 8SO2 .

(i) Calculate the maximum mass of copper that can be obtained from 367 kg of copper pyrites.

(ii) State why the gaseous product from this reaction must not be allowed to escape into the atmosphere.

 (b)Find the oxidation state of sulphur in the sulphate ion, SO ²₄⁻ .

6. (a) List two classes of oxides. Give one example in each case.

(b)Write the chemical formula of tetrachloromethane and state the type of bond that exists.

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

(b)   State three industrial application of electrolysis.

8.(a) You are provided with CH3CH2OH, CH3CH2CH3, CH3COOH, and CH2 =CH2.

1. Which compounds are gases at room temperature?
2. How can you distinguish compound CH3CH2CH3 and CH2= CH2?
3. Which compound would react with sodium carbonate? Write the balanced chemical equation for the reaction.

(b) Hydrogen peroxide breaks down slowly to form water and oxygen; the reaction can be speed up by using a catalyst.

1. How does the catalyst speed up the rate of reaction?
2. Name a possible catalyst that can be used to speed up the reaction.
3. Show that the catalyst always remains unchanged at the end of the reaction.

9. (a)An atom M has an atomic number 14 and mass number 28. 

(i)What is the number of protons and neutrons?

 (ii) Write the electronic configuration of atom M.

(b) Calculate the volume of water which was produced when 1,120 cm³ of oxygen at s.t.p. was liberated during the decomposition of hydrogen peroxide. The density of water = 1.0 g/cm³ 

10. (a) Complete the following equations and determine the type of chemical reaction involved in each case.

(i)  Zn(s) + H2SO4( aq) →

(ii)  AgNO₃₍ aq₎ + NaCl₍ aq₎ ^→              

(iii)  N2(g) + H2(g) →    

(b) How long a current of 5A should be passed through a solution of silver chloride in order to deposit 3.24 g of silver metal at the cathode? Given that, the electrochemical equivalent of silver = 1.118 x 10^-3 ge^-1 .

11.  (a) Briefly explain why the mixture with equal boiling point cannot be separated by simple fractional distillation.

(b)  The preparation of ammonia in the laboratory is done by heating any ammonium salt with an alkali.

(i)  Write a balanced chemical equation for the preparation of ammonia gas.

(ii)  State two uses of ammonia.

SECTION C (26 Marks)

Answer all questions from this section. 

12. A student attempted to prepare hydrogen gas by reacting zinc metal with dilute sulphuric acid. In this experiment zinc metal granules of about 0.5 cm diameter and 0.20 moles of acid were used.

The rate of formation of hydrogen gas was found to be slow.

(a)Explain three ways in which the rate of formation of hydrogen gas could be increased.

(b)If the student wanted 36 cm³  of hydrogen gas at s.t.p, what amount of the acid would be required.

 13.Using four examples, explain how the process of neutralization is important in day to day life.

THE UNITED REPUBLIC OF TANZANIA

NATIONAL EXAMINATIONS COUNCIL CERTIFICATE OF SECONDARY EDUCATION EXAMINATION.

032/1 CHEMISTRY 1

(For Both school and Private Candidates)

Time: 3Hours Friday, 04  ^th   November 2016 a.m

Instructions.

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

2. Answer all questions in this paper

3. Calculators and cellular phones are not  allowed in examination room.

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

5. The following constants may be used.

Atomic masses: C = 12, O = 16, Mg = 24, Al = 26, S = 32,

Cl = 35.5, Mn = 55, Fe = 56, Cu = 63.5,

Avogadro ’s number = 6.02 _x_  10  ²³  ,

GMV at s.t.p = 22.4dm  ³ 

1Faraday = 96,500 coulombs

Standard pressure = 760mm Hg.

Standard temperature = 273 K,

1 litre = 1dm  ³  = 1000cm  ³ 

SECTION A:

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

(i) Which of the following is True about the following equilibrium?

1. Water molecules have stopped changing into ions.

2. Water molecules have all changed into ions

3. Concentrations of water molecules and ions are equal

4. Concentrations of water molecules and ions are constant

5. Water molecules are moving slow.

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

1. Conductivity

2. Malleability

3. Ductility

4. Decorating

5. Expansion.

(iii) If a steady current of 2 amperes was passed through an aqueous solution of iron (II) sulphate for 15 minutes, the mass of iron deposited at the cathode will be.

1. 30g.

2. 56g.

3. 0.54g.

4. 28g.

5. 0.52g.

(iv) What will happen when zinc is placed in aqueous copper (II) sulphate?

1. Copper atoms are oxidized

2. Zinc atoms are oxidized

3. Copper ions are oxidized

4. Zinc ions are oxidized

5. Sulphur atoms are oxidized.

(v) Which of the following pair of gas can be prepared in the laboratory and collected over water?

1. Oxygen and Ammonia

2. Hydrogen and Hydrochloric acid

3. Hydrogen and Ammonia

4. Oxygen and Hydrogen chloride

(vi) Two substances are allotropes of carbon if

1. Both reduce heated iron (II) oxide to iron

2. Have different crystalline structure

3. Have equal masses

4. Have equal shape

5. Have the same arrangement of atoms

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

1. Burette

2. Volmetric flask

3. Pipette

4. Measuring cylinder

5. Graduated beaker

(viii) The reaction  represents which among the following reactions.

1. Synthesis

2. Precipitation

3. Neutralization

4. Displacement

5. Decomposition

(ix) The occurrence of two or more compounds with the same molecular formula but different molecular structures is known as.

1. Amphoterism

2. Isomerism

3. Allotropy

4. Polymorphism

5. Isotopy

(x) Which of the following sets of symbols represent isotopes of a single element?

1.  ¹⁶  ₈  X,  ¹⁷  ₈  X,  ¹⁸  ₈  X

2.  ¹⁶  ₈  Z,  ¹⁷  ₈  Z,  ¹⁸  ₈  X

3.  ¹⁶  ₇  P,  ¹⁶  ₈  P,  ¹⁶  ₉  P

4.  ¹⁶  ₇  K,  ¹⁷  ₈  K,  ¹⁸  ₉  K

5.  ¹⁶  ₇  U,  ¹⁶  ₈  U,  ¹⁸  ₁₀  U

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

 SECTION B: 

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

1. Soil Ph

2. Liming.

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

(ii) Describe how sulphur dioxide is changed into sulphur trioxide. Give the reaction conditions and the equation(s)

4. (a) Differentiate dilute hydrochloric acid from dilute sulphuric acid.

(b) John measured the volume of gas produced when 5 g of two chemicals X and Y were added separately to hydrogen peroxide under identical conditions. His results for this experiment are represented on the graph below.

John claimed that Y is a better catalyst than X. His partner Steven did not agree.

1. Why does Steven think that John’s conclusion is wrong?

2. After the experiment, Steven recovered 5 g of X and 1 g 1 of Y from the two experiments. He claimed that John was wrong. Does Steven’s claim true? Give a reason.

5. (a) Give the name of the type of reaction represented by each of the following chemical equations.

(b) 25cm  ³  samples of water A, B, C and D were tested with soap solution. The volume of soap solution required to produce a lather that lasted for a minute was recorded. Fresh samples of each were boiled and tested again with soap solution. The results are shown in Table 1.

Table 1.

1. Which sample probably contains temporary hardness of water only?

2. Which sample probably contains both permanent and temporary hardness of water? Give a reason for your answer.
   
   

6. (a) Write the structural formula for the following compounds:

1. But-2-ene.

2. Pent-2-yne

3. 1,2-dichloroethane

4. 2,4-dimethylhexane.

(b) Briefly explain what will be observed when silver nitrate solution is added to aqueous solution of sodium chloride.

7. (a) Determine the empirical formula of a substance that has the following composition by mass; 49.5% oxygen.

(b) Give one reason why Alluminium is chosen to make each of the following items:

1. Cooking foil

2. Overhead electric cables

3. Window frames

8. (a) Identify and state the environmental problem caused by the gas which is released from the blast furnace in the extraction of iron from its oxide.

(b) (i) Draw a labeled diagram of a simple electrolytic cell which show how copper is purified.

(ii) Write balanced ionic equations to show the electrode reactions which occur when copper is purified.

9. (a) Name two elements which are expected to show similar chemical reaction with magnesium. What is the basis for your choice?

(b) State the main raw material and the process involved in the manufacture of the following products.

1. Wood charcoal

2. Coke

3. Lampblack.

10. (a) Give two chemical tests of water and the expected result to be observed.

(b) A student tested five solutions M, N, O, P and Q with a universal indicator solution to find their pH values. The following results were obtained.

Which of the above solutions was?

1. Neutral solution

2. Strong acid

3. Strong alkali

4. Weak acid.

11. (a) State the meaning of the following and give one example in each case.

1. Amphotenic oxide

2. Acidic oxide.

(b) A student investigated different reactivity of a set of metals by placing pieces of each metal in metal nitrate solution. Table 2 shows some of the results.

Table: 2.

Where: _{ } = reaction observed and X = no reaction.

1. Use the most results given to arrange the metals in order of reactivity starting with the most reactive metal.

2. Use the reactivity series in 11 (b) (i) to complete Table 2.

 SECTION C: 

12. Explain five methods to prevent terrestrial pollution.

13. 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)  MSO  _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.

THE UNITED REPUBLIC OF TANZANIA NATIONAL EXAMINATIONS COUNCIL CERTIFICATE OF SECONDARY EDUCATION EXAMINATION 

032/1 CHEMISTRY 1

(For Both School and Private Candidates)

TIME: 3 Hours     Thursday, 05^thOctober 2015 p.m.

Instructions

1.  This paper consists of sections A, B and C.
2.  Answer all questions in this paper.
3.  Calculators and cellular phones 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, Li = 7, C = 12, O = 16, Na = 23, Al = 26, Cl = 35.5, K = 39, Cu = 63.5

 Avogadro’s number = 6.02 x 103 ²³.

GMV at s.t.p. = 22.4 dm .

1 faraday = 96,500 coulombs.

Standard pressure = 760 mm Hg.

Standard temperature = 273 K.

1 litre = 1 dm³ = 1000 cm³.

This paper consists of 6 printed pages.

SECTION A (20 marks) 

Answer all questions in this section.

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

(i)  The mass number of a carbon atom that contains six protons, eight neutrons, and six electrons is

1.   6
2. 14
3. 8
4. 12
5. 20.

(ii)  How many moles of oxygen are required for the complete combustion of 2.2 g of C3H 8 to form carbon dioxide and water?

1. 0.050 moles
2. 0.15 moles
3. 0.25 moles
4. 0.50 moles
5. 0.025 moles.

(iii)  In the graph below, curve 1 was obtained from the decomposition of 100 cm³ of 1.0M hydrogen peroxide solution catalysed by manganese (IV) oxide, 2H2O 2?2H  2O+O  2 .

Which alteration/change to the original experimental conditions would produce curve 2?

1. Lowering the temperature
2. Using less manganese IV oxide
3. Increasing the temperature
4. Adding some 0.1 M H2O 
5. Using a different catalyst.

(iv)  How long must a current of 4.00 A be applied to a solution of Cu ₍²_a⁺_q) to produce 2.0 grams of copper metal?

1. 2.4x10²s
2. 1.5x10³s
3. 7.6x10²s
4. 3.8x10²s
5. 12x10⁴s

(v)  Which of the following hydrocarbons does NOT belong to the same homologous series as the others?

1.   CH₄ B
2. C3H 8 
3.   ^C4^H₁₀ 
4. C6H 12 
5. C2H 12.

(vi)  A solution of pH 1.6 is best described as

1. weak acid
2. strong base
3. weak base
4. strong acid
5. neutral solution.

(vii)  Which among the following equations correctly shows the reaction between chlorine gas and water?

(viii)  Hygroscopic and deliquescent substances can be used as

1. oxidising agents
2. drying agents
3. reducing agent
4. weak electrolytes
5. catalyst.

(ix)  Which among the following pair of substances are allotropes?

1. H 2 O and H 2 O 2
2. 12 C and 14 C
3. P 4 and P 8
4. H 2 and 2H +
5. H + and H 3 O.

(x)  Water can be obtained from a solution of common salt by

1. evaporation
2. simple distillation
3. filtration
4. condensation
5. fractional distillation.

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

SECTION B (54 marks) 

Answer all questions in this section.

3. (a) (i) State two conditions required for iron to rust.

 (ii) List two methods which are used to prevent rusting of iron.

(b) State three properties that make aluminium useful in overhead cables.

4. (a) Give three examples in each of the following:

 (i) Solid fuel 

 (ii) Gaseous fuel.

 (b) The reaction which produces methanol from carbon monoxide and hydrogen is represented by the equation CO(_g) + 2H 2( g₎ ⇌ CH3OH ( g₎ ΔH = ­94kJmol ^­1. The reaction is carried out at high pressure to give a good yield of methanol.

(i)  Explain why increase in pressure gives a better yield of methanol.

(ii) The value of ΔH is negative. What does this tell about the reaction?

(iii) With a reason, state whether a high temperature or low temperature will give a better yield of methanol.

5. (a) (i) Explain, in terms of electronic configurations, why sodium and potassium elements have similar chemical properties.

 (ii) State the trend in reactivity of group I elements in the Periodic Table and give reasons for it.

6.  (a) Table 2 indicates the pH values of soil for some crops to grow. Table 2

Which crop grows best in the:

(i)  Most acidic soil?

(ii) Least acidic soil?

(iii) Neutral soil?

 (b) Suggest one best method for separating each of the following mixtures:

(i)  Common salt and water

(ii) Iodine and sand.

(iii) Pieces of iron and sand.

7.  (a) Briefly explain what will happen when

(i) concentrated sulphuric acid is exposed to the atmosphere?

(ii) iron (II) sulphate is exposed to air for a long time?

(iii) a bottle containing AgNO3 is left open?  

 (b)Give three applications of the process of neutralization in daily life.

8. (a) Give the names or formula of the two chemicals that would be used in the laboratory to make each of the following gases. State a simple test that could be used to identify each gas. 

(i)  Oxygen.

(ii) Hydrogen.

(iii) Carbon dioxide.

(b) Suggest a suitable indicator for the following titrations:

(i) Hydrochloric acid against ammonia solution.

(ii) Sulphuric acid against sodium hydroxide solution.

(iii) Ethanoic acid against potassium hydroxide solution.

9. (a) (i) What type of a chemical bond is found between fluorine atoms in a fluorine molecule?

(ii) Name other type(s) of chemical bond formed by fluorine with other elements. Give an example of a compound in which fluorine form this type of bond.

(i) Calculate the molecular formula of the compound X.

(ii) Draw and name the displayed/open structure formula of the possible isomer(s) from the molecular formula determined.

10.  (a) A student tested four samples of water, each 5 cm³ from different areas of Kahama district by shaking with 3 drops of soap solution. The experiment was repeated by boiling each sample of water (5 cm³) with 3 drops of soap solution. The observations were recorded in Table 3. 

(i)  Which samples contain hard water?

(ii) Which sample contains temporary hard water? Give a reason.

 (b) Protons neutrons and electrons particles are located in the atoms; fill in the missing information in Table 4 about these particles. 

Table 4

11. (a) A steady current of 2A was passed through a solution containing ions of a metal (X²⁺) for nine minutes. The mass of metal X that was liberated were 0.3552 g. Calculate the molar mass of metal X.

(b) Name the following compounds according to the IUPAC system.

 SECTION C (26 marks)

Answer all questions from this section.

12. Describe the extraction of iron from the haematite ore and write all the chemical equations for the reactions involved in each stage of extraction.

13. Addition of inorganic fertilizers in the farm is not as important as addition of organic manure. Discuss the correctness of this statement in four points.

THE UNITED REPUBLIC OF TANZANIA NATIONAL EXAMINATIONS COUNCIL

CERTIFICATE OF SECONDARY EDUCATION EXAMINATION 

032/1  CHEMISTRY 1

 (For Both School and Private Candidates)

Time: 3 Hours  Thursday, 06^th November 2014 p.m.

 Instructions

1. This paper consists of sections A, B and C.
2. Answer all questions in this paper.
3.  Calculators and cellular phones 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, N = 14, Na = 23, S = 32, O = 16, Al = 26, Cl = 35.5 Ca = 40, Mn = 55, Fe = 56, K = 39.

 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 (20 Marks)

Answer all questions in this section.

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

(i)  An element in the periodic table with atomic number 18 belongs to which of the following?

1. Group I and period I.
2. Group O and period III.
3. Group III and period III.
4. Group V and period IV.
5. Group VII and period IV.

(ii)  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).

(iii)  The reason why white anhydrous copper (II) sulphate turns blue when exposed in atmosphere is that it,

1.   reacts with carbon dioxide.
2. reacts with oxygen
3. becomes dry.
4. absorbs water vapour.
5. decomposes.

 (iv)  Chemical change means;

1.   the change is reversible.
2. can easily be separated.
3. the change is complete.
4. new substance is produced.
5. produces no change of mass.

(v)  If a stead current of 2 amperes was passed through an aqueous solution of iron (II) sulphate for 15 minutes, then the mass of iron deposited at the cathode will be:

1. 54 g.
2. 56 g.
3. 0.54 g.
4. 28 g.
5. 0.52 g.

(vi)  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

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

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

(viii)  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.

ix) Alcohols react with carboxylic acids to form a group of organic compounds called

1. alkynes
2. aldehydes
3. ethers
4. esters
5. alkanols.

(x) Which of the following statement is true about water gas?

1. It is poisonous.
2. Contains hydrogen.
3. Is the same as biogas.
4. Contains hydrogen and nitrogen.
5. Contains carbon monoxide and hydrogen.

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.

SECTION B (54 Marks) 

Answer all questions in section.

3. (a) (i) Why chemistry laboratory exits open outward?

 (ii) State the uses of any four items found in a First Aid Kit.

(b)  (i) Arrange the following metals in order of increasing reactivity; zinc, magnesium, calcium, copper and mercury.

 (ii) Which one of the metals in (b) (i) above reacts with steam to form an oxide which is white when cold and yellow when hot?

4.  (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)  Give two examples in each of the following solution.

(i)  Gaseous solution.

(ii) Solid solution.

5. (a) Study the following part of the periodic table and List down the names of all the missing elements. Table 1

(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.

6. (a) With the aid of chemical equations, explain what will happen when aluminium chloride reacts with water.

(b) A student accidently broke a beaker containing copper (II) sulphate crystals. He decided to separate the blue crystals from the small pieces of glass by first dissolving the mixture and then filtering. What were his next steps?

7. (a) Table 2 gives some information about the composition of three samples of water from wells in Kahama, Maswa and Bukombe districts.

 Table 2

(i)  State two ways in which these ions get into the samples of water.

(ii)  Giving two reasons, state the hardest sample of water.

(iii)  State two ways that can be used to remove ions in (ii).

(b) State and describe the type of reaction in the following chemical equations: 

 (i) Fe(s) + CuSO4(aq) à FeSO4(aq) + Cu(s).

 (ii) Na2SO4(aq) + BaCl2(aq) à BaSO4(s) + 2NaCl(aq).

8.  The following are the general structural formulae of certain organic compounds: R-OH, R-COOH, and RCOOR.

 (a) Name the:

(i) Homologous series represented by R-OH, R-COOH and RCOOR. 

 (ii) Functional groups represented by R-OH and R-COOH.

(c) When a burning splint is introduced into a gas jar containinakes use of these two properties?

9. (a) Differentiate between:

(i) A base and an alkali.

(ii) Atom and isotopes.

(b) An organic compound P consist of 52.2% of carbon, 13% of hydrogen and 34.8% of oxygen. The vapour density of P is 23. Calculate the molecular formula of the compound P and write possible isomer(s) from the molecular formula determined.

10.  (a) Aluminium reacts with oxygen to form aluminium oxide. How many grams of potassium chlorate would be heated to produce enough oxygen to form 5.1 g of aluminium oxide?

(b) The preparation of chlorine gas can be represented by the following equation: 

 MnO₂ + 4HCl à MnCl₂ + 2H₂0 + Cl₂. How many moles of HCl are needed to react with 25 g of MnO₂?

11. (a) (i) List four effects of excessive nitrogen to plants.

 (ii) State two ways through which soil nitrogen can be lost.

(b)  Oxygen and ethanol react to produce carbon dioxide and water according to the following energy level diagram: 

(i)  What is represented by letter A, B and C?

(ii)  What type of reaction is represented by this energy level diagram?

SECTION C (26 Marks) 

Answer all questions in this section.

12.Assume that you are a chemist in a chemical plant that deals with the production of chlorine gas You want to produce 100 litres of chlorine gas per hour so that you can reach the company’s goal of producing 2400 litres every day. What current of electricity will you allow to flow per hour?

13. Describe five causes and effects of soil pollution.

 THE UNITED REPUBLIC OF TANZANIA NATIONAL EXAMINATIONS COUNCIL

CERTIFICATE OF SECONDARY EDUCATION EXAMINATION 

032/1  CHEMISTRY 1

 (For Both School and Private Candidates) 

Time: 3 Hours  Thursday, 07^th November 2013 p.m.

 Instructions

1. This paper consists of sections A, B and C.
2.  Answer all questions in this paper.
3.  Calculators and cellular phones 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, Na = 23, Mg = 24, Al = 26, S = 32, Cl = 35.5, Ca = 40, Fe = 56, Cu = 64, Ag = 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 = 1 dm³ = 1000 cm³.

SECTION A (20 Marks)

Answer all questions in this section. 

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

 (i)  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.

 (ii)  In the titration of a monoprotic acid with a solution of sodium hydroxide of known concentration, what quantities will be equal at the equivalence point?

1. concentration of hydroxide solution and hydronium ions.
2. number of moles of hydroxide ions added and number of moles of hydronium ion initially present.
3. number of moles of hydroxide solution added and volume of acid solution initially present.
4. number of moles of hydroxide ion added and the number of moles of monoprotic acid initially present.
5. volume of sodium hydroxide solution added and volume of acid solution initially present.

 (iii)  The charge of one mole of electrons is represented by the term

1.   one ampere
2. one coulomb
3. one volt
4. one faraday E
5. one gram.

 (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)  Consider the system at equilibrium: H₂O_(l) H₂O_(g) for which Which change(s) will increase the yield of H₂O_(g).

1. Increase in temperature
2. Increase in the volume of the container
3. Increase in temperature and volume of the container
4. Increasing surface area of oxygen
5. Increasing surface area of reactants.

 (vi)  As water is added to an acid, the acid becomes

1.   more acidic and its pH goes down
2. more acidic and its pH goes up
3. less acidic and its pH goes up
4. less acidic and its pH goes down
5. neutral and its pH becomes 7.

 (vii)  Three elements, X, Y and Z, are in the same period of the periodic table. The oxide of X is amphoteric, the oxide of Y is basic and the oxide of Z is acidic. Which of the following shows the elements arranged in order of increasing atomic number?

1.   X, Y, Z
2. Y, Z, Y
3. Z, X, Y
4. Y, X, Z
5. X, Z, Y.

 (viii)  Which of the following compounds contains only two elements?

1.   Magnesium hydroxide
2. Magnesium nitride
3. Magnesium phosphate
4. Magnesium sulphite
5. Magnesium sulphate.

 (ix)  An atom has 26 protons, 26 electrons and 30 neutrons. The atom has

1.   atomic number 26, mass number 52
2. atomic number 56, mass number 30
3. atomic number 30, mass number 82
4. atomic number 52, mass number 56
5. atomic number 26, mass number 56.

 (x)  The following equation is a propagation step in the chlorination of methane:

1. Cl₂ Cl^• ₊ Cl^•
2. CH^•₃ + Cl^• CH₃Cl
3. CH^•₃ + Cl₂ CH₃Cl + Cl^•
4. CH₄ + Cl^• CH₃Cl + H^•
5. CH^•₃ + Cl₂ Ch₂Cl + Cl^•.

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

 SECTION B (54 Marks) 

Answer all questions in section. 

3. (a)Study the following portion of the periodic table with some elements represented by letters and answer the questions that follow.

 (i) State how electronegativity varies from A to C and from B to D . 

(ii) Write the electronic configurations of A, C^2-, D and B.

 (b) 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.

4. (a) 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).

 (ii) Explain four factors affecting soil erosion.

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

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

(i) Iodine and sand.

(ii) Green solution from leaves.

(iii) Alcohol and water.

(iv)  Iron fillings and powdered calcium carbonate.

6. (a) (i) State three characteristics of a homologous series.

(ii) Draw the displayed/open structure formula of 2, 2-dichlorohexane.

(iii)  Giving two reasons, explain why 2, 2-dichloro-3-methylbutane is a structural isomer of 2, 2-dichloropentane. 

 (b)  Carbon monoxide and hydrogen are used in the manufacture of methanol and the equilibrium is established according to the following equation.

 CO_(g) + 2H_2(g) ⇋ CH₃OH_(g) ΔH=-80 kJ mol^-1.

(i) Give two features of the reaction at equilibrium.

(ii) Explain why an increase in temperature causes a decrease in equilibrium yield of methanol.

7. (a) Briefly explain how aluminum is obtained from its oxide.

(b) Write down the chemical equations of the reactions between the following:

(i)  Ethanol and sodium metal.

(ii) Propanol warmed with excess acidified potassium permanganate.

(iii) Propanol and acetic acid warmed together in the presence of concentrated sulphuric acid.

8.  (a) 25 cm³ of 0.1 M HCl were neutralized by 23 cm³ of sodium hydroxide solution. Calculate the concentration of the alkali in grams per litre.

 (b) Give the meaning of the following terms:

(i)  Soil structure.

(ii)  Acidic soil.

(iii) Liming.

9.  (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.

10. (a) Calculate the number of oxygen molecules and atoms in 0.5 moles of oxygen gas at room temperature.

 (b)  Giving three reasons, explain why air is said to be a mixture of gases.

11.(a) For each of the following reactions, identify which of the gases, chlorine, sulphur dioxide, and hydrogen sulphide is either an oxidizing agent or reducing agent. Explain how you arrived at your answers.

(i)  Cl2(g) + 2H2O(l) + SO2(g) → 2HCl(g) + H2SO4(aq).

(ii)  SO2(g) + 2H2S(g) → 2H2O(l) + 3S(s). 

 (b)  Fill in the missing value in the following table.

SECTION C (26 Marks) 

Answer all questions in this section. 

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

13. The formation of oxides of non-metals can be both beneficial and harmful to man. Justify the statement focusing on the oxides of carbon, nitrogen and sulphur.

THE UNITED REPUBLIC OF TANZANIA NATIONAL EXAMINATIONS COUNCIL

CERTIFICATE OF SECONDARY EDUCATION EXAMINATION 

032/1  CHEMISTRY 1

 (For Both School and Private Candidates)

Time: 3 Hours  Thursday, 11^th October 2012 p.m.

 Instructions

1.  This paper consists of sections A, B and C.
2.  Answer all questions in this paper.
3.  Calculators and cellular phones 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, Na = 23, Mg = 24, Al = 26, S = 32, Cl = 35.5, Ca = 40, Mn = 55, Fe = 56, Cu = 64.

 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 (20 Marks)

Answer all questions in this section.

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

(i)  Which one of the following sets of laboratory apparatus are used for measure volume?

1. Crucible, U-tube and volumetric flask
2. Test tubes, beakers and glass jar
3. Thistle funnel, separating funnel and beaker
4. Burette, pipette and measuring cylinder
5. Conical flask, test tube and measuring cylinder.

(ii)  The empirical formula of certain compound in CH₃. Its molar mass is 30 g. What will be its molecular formular?

1. CH₄
2. C₂H₄
3. C₂H₆
4. C₂H₈
5. C₄H₁₂

 (iii)  In order to produce the greatest amount of hydrogen in a short time, one gram of magnesium ribbon should react with

1. 10 cm³ of 0.5 M sulphuric acid
2. 40 cm³ of 0.5 M acetic acid solution
3. 40 cm³ of 0.5 M sulphuric acid solution
4. 20 cm³ of 1 M sulphuric acid solution
5. 20 cm³ of 1 M acetic acid solution.

(iv)  Fractional distillation process of a mixture of water and ethanol is possible because

1. water and ethanol have the same boiling point
2. water has lower boiling point than ethanol
3. ethanol has lower boiling point than water
4. water and ethanol form partially immiscible liquid solution
5. water and ethanol are immiscible liquids.

 (v)  Which of the following substances represent a group of acidic oxides?

1. Carbon dioxide, carbon monoxide and sulphur dioxide
2. Sulphur trioxide, nitrogen dioxide and nnitrogen 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.
   

 (vi)  What will the molarity of a solution which contains 26.5 g of anhydrous sodium carbonate in 5 dm³ of solution?

1. 0.05 M
2. 0.25 M
3. 5.30 M
4. 0.025 M
5. 0.50 M

 (vii)  The Brownian movement is taken to be the evidence of the:

1. theory of association of water molecules
2. theory of ionization of electrolytes
3. theory of colloidal suspensions
4. kinetic theory of behavior of substances
5. Brownian theory.

 (viii)  One off the isotopes of an element X has an atomic number Z and a mass number A. What is the number of neutrons contained in the nucleus of the element X?

1. Z
2. A
3. A + Z
4. A – Z
5. Z – A

(ix)  C₂H₄Cl can be represented in different structures which are called

1. homologous series
2. isomers
3. structural formulae
4. identical structures
5. condensed structures.

(x)  _____ is the general term used to explain a mixture of different metals.

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

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

SECTION B (54 Marks) 

Answer all questions in section.

3. (a) With the help of chemical equation, what will be observed when ammonia reacts with

(i) Hydrogen chloride.

(ii) Copper (II) oxide.

(b) It is not advisable to sleep inside a house which is not well ventilated with a burning wooden charcoal. Give a reason for that and write the chemical equation to represent your answer.

4. Study the following part of the periodic table and then answer the questions that follow. Note: The letters used are not scientific symbols for the elements concerned.

Group

(a) Identify and write down the electronic configuration for the elements K, N, P and L.

(b) What type of bond will exist in a compound formed when Q combines with L? Write the chemical formula for the compound formed and list two chemical properties for the compound formed.

5.  (a) A solution of sodium hydroxide was electrolysed using platinum electrodes. Write the reactions which took place at the electrodes and give a reason why the solution becomes alkaline. 

(b) Electric current was passed through a solution of sodium hydroxide using platinum electrodes. Draw a labelled electrolytic cell for this electrolysis. Indicate the directions of the movement of ions. 

6. (a) Give the name of the process of making coke from coal. Write one characteristic which make coke a better fuel than coal.

(b)(i) State the difference between physical strength and chemical strength of metals.

(ii) Giving example, explain why preparation of metallic oxides by direct method is not intensively used. 

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

 (ii)Give four compounds found in laboratories which show the same characteristics as ashes.

 (b) How many molecules are there in 11.2 litres of carbon dioxide at STP? 

8. (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.

9. Two experiments were carried out using the same mass of magnesium ribbon and the same volume of acids of the same concentration. The acids were 1M hydrochloric acid and 1M ethanoic acid. The results were as shown in the following figure:

 (a) If the experiments were conducted within the same time, is there a difference in volumes of hydrogen gas collected at the same room temperature and pressure? Give reasons for your answer.

 (b) When same mass, volume and concentration of powdered magnesium and ethanoic acid are allowed to react, new graph is formed. Giving reason (s), suggest the position of that graph whether will be above, between or below graphs A and B. 

10. (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.

11. (a) The chemical properties of concentrated sulphuric acid can be grouped into oxidizing property and dehydrating property. In which property should sulphuric acid be grouped when it reacts with copper metal? Give reason and write the equation of the reaction.

 (b) The preparation of chlorine gas can be represented by the following equation: MnO₂ + 4HCl → MnCl₂ + 2H₂O + Cl₂. Calculate the number of moles of HCl which are needed to react with 20 g of MnO₂ and list two main chemical properties of chlorine gas.

SECTION C (26 Marks) 

Answer all questions in this section. 

12. Consider a four carbon hydrocarbon (C₄H_n), where n is an integer. Give the name of homologous series, molecular formula and structural formula for different isomers of the compound formed by each homologous. In each case indicate the causes of isomerism. 

13.Describe four common stages for the extraction of metals. Does the extraction of gold follow all four stages? Give reasons.

THE UNITED REPUBLIC OF TANZANIA NATIONAL EXAMINATIONS COUNCIL CERTIFICATE OF SECONDARY EDUCATION EXAMINATION 

(For School Candidates Only)

TIME: 3 Hours Thursday, 7^th  October 2010 p.m.

 Instructions

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

2. Answer all questions in sections A and B, and two (2) questions from section C.

3. Calculators and cellular phones 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, Na = 23, Mg = 24, C = 12

Cl = 35.5, K = 39, Pb = 207.

Avogadro’s number = 6.02 x 103 ²³.

GMV at s.t.p. = 22.4 dm .

1 Faraday = 96,500 coulombs.

Standard pressure = 760 mm Hg.

Standard temperature = 273 K.

1 litre = 1 dm³ = 1000 cm³.

.SECTION A (20 marks)

Answer all questions in this section.

1. For each of the items (i) ­ (x), choose the correct answer 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) A catalyst can be described as a substance 

1. that alters the rate of reaction
2.  that slows down the rate of reaction
3.  used in every reaction so as to speed up rate of reaction
4.  that starts and speeds up the rate of reaction
5.  that terminates chemical reaction.

(iv) A covalent bond is formed when

1.  a metal combines with a non­metal
2.  potassium and oxygen combine
3.  ammonia is formed
4.  two metals combine
5.  atom looses an electron.

(v) A solvent can be obtained from a solution by

1.  evaporation followed by decantation
2.  filtration and condensation
3.  evaporation and filtration
4.  evaporation and condensation
5.  crystallization followed by sublimation.

(vi) Aqueous sugar solution is a poor conductor of electricity because

1.  water and sugar are covalent compounds
2.  water is a non­electrolyte
3.  sugar is a non­electrolyte
4.  sugar is covalent when in liquid form
5.  sugar dissolves completely in water.

(vii) The process of giving away water of crystallization to the atmosphere by a chemical substance is called

1.  efflorescence
2.  deliquescence
3.  hygroscopic
4.  sublimation
5.  vapourisation.

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

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

(ix) Among the factors that determine the ions to be discharged at electrodes when salt solutions are electrolysed are their

1.  non metallic nature
2.  relative concentrations in the solution
3.  relative ionic masses
4.  electronic configuration
5.  position in the periodic table.

(x) The mass of sodium hydroxide contained in 25 cm³ of 0.1 M NaOH is

1.  0.5 gm
2. B 2.85 gm
3.  250 gm
4.  0.2 gm
5.  25 gm

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

SECTION B (60 marks)

Answer all questions in this section.

3. (a) Asubuhi Njema’s child was sick. When she took her to the hospital, she was prescribed some medicine including a bottle of syrup. The bottle was written, Shake before you use. What does this statement signify? (3 marks)

(b) (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. (4 marks)

(c) 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? (3 marks)

4. (a) Draw a well labeled diagram of a non­luminous Bunsen burner flame (3 marks)

(b) Explain the meaning of the following:

(i) Malleable

(ii) Ductile

(iii) Brittle (3 marks)

(c) 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. (4 marks)

5. (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)

(c) In the following reaction, name a reducing agent substance and an oxidizing agent:

CuO₍ s₎ + H 2( g₎ → Cu ( s₎ + H 2 O ( g)  (3 marks)

6. (a) Which homologous series of organic compounds can be represented by the following general formula?

(i) Cn H_2n+2

(ii) C_nH_2n

 (iii) C_n H_{2 n+1}OH (3 marks)

(b) Give the name of the first compound in each series. (3 marks)

 (c) (i) Describe a reaction by which a named compound of series in (a) (ii) can be converted to a compound of series in (a) (ii).

(ii) How can a compound of series (a) (iii) be converted to a compound of series in (a) (ii)? (4 marks)

7. (a) Differentiate empirical formula from molecular formula. (2 marks)

(b) Calculate the percentage composition by mass of water in a hydrated magnesium chloride MgCl2•6H 2O.  (3 marks)

(c) 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) (5 marks)

8. (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? (4 marks)

(c) Give reasons for the following:

(i) Solution of chlorine in water is acidic

(ii) Yellow phosphorus is stored under water.

SECTION C (20 marks)

Answer all questions from this section.

9. (a) (i) What are the natural causes of soil acidity?

(ii) What cations prevail in acidic soils? (2 marks)

(b) (i) On treatment with calcium hydroxide the soil pH was raised from 5 to 7.

What can you say about the properties of calcium hydroxide?

(ii) What effects can the alkalinity of a soil have on the availability of nutrients?

(iii) Is it sensible to add lime to a field which has received an application of

ammonium sulphate fertilizer? Explain. (5 marks)

(c) Which reference to pH, solubility and any other factors, list the main properties of the following fertilizers used in our country:

(i) Ammonium sulphate

(ii) Super phosphate

 (iii) Urea (3 marks)

10. (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)

(c) Calculate the total number of

(i) molecules in 0.18g of water

(ii) electrons present in 0.0001 moles of pure magnesium metal (4 marks)

11. (a) Elements A, B, C and D have atomic numbers 6, 8, 17 and 20 respectively. Write electronic structures of these elements. (4 marks)

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

(i) A and B combine chemically

(ii) C and D combine chemically. (2 marks)

 (c) (i) What types of bonding you would expect to occur in each of the compounds formed in (b)

(ii) List three (3) differences in properties you would expect to find between the compounds in (i) as a result of their difference in types of bonding. (4 marks)

12. Read the following information carefully then answer questions that follow: 25 cm³ of potassium hydroxide were placed in a flask and a few drops of phenolphthalein indicator were added. Dilute hydrochloric acid was added until the indicator changed colour. It was found that 21 cm³ of acid were used.

(b) (i) What piece of apparatus should be used to measure out accurately 25 cm³ of sodium hydroxide solution?

(ii) What colour was the solution in the flask at the start of the titration?

(iii) What colour did it turn when the alkali had been neutralized? (3 marks)

(c) (i) Was the acid more concentrated or less concentrated than the alkali? Give reasons for your answer.

(ii) Name the salt formed in the neutralization.

(iii) Write an equation for the reaction. (4 marks)

(d) Utilizing the given information describe how you can obtain pure crystals of the salt. (3 marks)