NAME: …………………………………………………………… STREAM: ………… ADM: ……..……
SIGNATURE: ……………………………………………………… INDEX NO: ………………………………………. DATE:…………………
233/2
CHEMISTRY
Time: 2 Hours
MOKASA II EXAMINATIONS
CHEMISTRY PAPER TWO
Instructions to students:
- Write your name, admission number and class in the spaces provided.
- Answer all questions in the spaces provided
- This paper consists of 12 printed
- Candidates should check the question paper to ascertain that all the pages are printed as indicated and that no questions are missing.
- Candidates must answer all questions in English
| Question | Maximum
Score |
Student’s
Score |
|
1 |
12 |
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2 |
11 |
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3 |
12 |
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4 |
13 |
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5 |
11 |
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6 |
11 |
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|
7 |
09 |
|
| TOTALS |
80 |
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- (a) Use the standard reduction potentials given below to answer the questions that follow.
Half –cell reactions E0(V)
B2+ (aq) + 2e– B(S) – 0.44
A2+(aq) + 2e– A(S) – 0.76
C2(aq) + 2e– 2C–(aq) +0.54
2E+(aq) + 2e– E2(g) 0.00
D3+(aq) + 3e– D(S) -1.66
- Identify the strongest oxidizing agent. Give a reason. (1mk)
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- Arrange the elements having the negative standard reduction potentials in order of increasing reactivity. (2mks)
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- Calculate the m.f of a cell formed by combing the half-cells of B and D. (2mks)
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- Write down the overall equation for the reaction taking place in (iii) above. (1mk)
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- Draw an electrochemical cell represented by the cell notation A(s) / A2+(aq) // B2+ / B(S).
(3mks)
- Draw a well – labeled diagram to showing how a spoon made of D is electroplated using A. (3mks)
(b) Determine the oxidation state of Mn in MnO4– (1mk)
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- Study the flow chart below for the extraction of aluminum from ore ore.
- Name the chief ore from which aluminium is extracted. (½ mk)
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- Give two impurities present in the ore. (1mk)
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- Briefly explain how the impuritiesin (ii) above are removed. (2mks)
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- Identify: (1mk)
Solution F…………………………………………………………………………………….
Residue S…………………………………………………………………………………….
- Write balance equations for
- The reaction taking place in process X (1mk)
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- Reaction producing gas F (1mk)
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- State any one uses of aluminium (½ mk)
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- Compare the atomic radius of aluminium with that of sodium.(Al = 13, Na = 11). (2mks)
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- Aluminium reacts with chlorine to form molecular compound. Using dots ( ) and (X) to represent electrons. Show the bonding in the compound formed. (Al = 13, Cl = 17)
(2mks)
- (a) Define the term “Dynamic Equilibrium”. (1mk)
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(b) List two factors, other than concentration, that affects chemical equilibrium. (1mk)
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(c) Explain the importance of the factors mentioned above to an industrialist. (1mk)
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(d) Consider the reaction below an equilibrium .
Br2(g) + H2O(l) 2H+(aq) +OBr–(aq) +Br–(aq)
(Orange)(Colourless)
State and explain the observation made when sodium hydroxide solution is added to the equilibrium mixture. (2mks)
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(II) The flow chart below shows some of the process involved in the large scale manufacture of sulphuric (VI) acid. Study and use if to answer the questions that follow.
- Why is the process referred to as Contact Process? (½mk)
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- Identify (2mks)
Solid C………………………………………………………………………………………..
Gas M…………………………………………………………………………………………
Gas L………………………………………………………………………………………….
Liquid V………………………………………………………………………………………
- Write down the equation for the reaction taking place in the absorption tower. (1mk)
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- Other than recycling, describe how pollution can be minimized in the process. (1mk)
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- 15,000 litres of suphuric (IV) oxide is reacted in chamber Y. With an efficiency of 80% determine the final mass of sulphuric (VI) acid produced in (2 ½mks)
(MGV= 24 L)
- (a) In an experiment to determine the heat of methanol, a student set-up the apparatus as shown below. Study the set-up and usethe data obtained to answer the questions that follow.
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Initialtemperature of water = 220C
Finial temperature of water = 360C
Initial mass of lamp + methanol = 85.10g
Final mass of lamp + methanol = 84.75g
Density of water = 1g/cm3 C = 4.2 Jg-1k-1
- Determine the heat change for this experiment. (1mk)
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- Determine the molar enthalpy of combustion of methanol. (2mks)
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- Write down a thermochemical equation for the reaction. (1mk)
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- Draw an energy level diagram for the reaction. (2mks)
- The molar enthalpy of combustion of thane (C2H6) is –1560kJmol-1. Explain which one is a better fuel between methanol and ethane.
(C= 12, O = 16, H = 1) (2mks)
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(b) Use the information below to answer the question that follow
Ca(s )+ ½ O2(g)CaO(s) ∆H1 = – 635kJmol-1
C(s) + O2(g) CO2(g) ∆H2 = -394kJmol-1
Ca (s) + C(s) + 3/2O2(g)CaCO3(S) ∆H3 = – 207kJmol-1
- Name two enthalpy changes represented by ∆H2 (2mks)
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- Use the information above to calculate the enthalpy change for the reaction (3mks)
CaO(s) + CO2(g) CaCO3(s)
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- Study the set-up below and use it to answer the questions that follow.
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- State the observation made in the combustion tube. (1mk)
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- Write an equation for the reaction producing the flame. (1mk)
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- Explain the observation made in the conical flask when the experiment is done for a longer period of time (2mks)
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- The flow chart below show the manufacture of sodium carbonate. Study it carefully and answer the questions that follow.
- Identify (1 ½ mks)
Gas X……………………………………………
Gas Y…………………………………………….
Liquid Q…………………………………………
- Give one use of calcium chloride. (½ mk)
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- Write balanced chemical equations for the reactions in (2mks)
Chamber III
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Chamber IV
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- Give two reasons why the Solvay process is considered one of the most efficient industrial process? (2mks)
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- Name two process taking place in chamber II. (1mk)
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- Study the flow chart below and use it to answer the questions that follow.
- Give the names of substances (2mks)
N…………………………………………………………………………………………………..
F…………………………………………………………………………………………………..
A………………………………………………………………………………………………….
E…………………………………………………………………………………………………..
- Give the conditions necessary for: (1 ½mks)
Process I
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Process IV ( ½mk)
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- Draw the open structural formula of (1mk)
- Write balanced chemical equations for the reaction in
- Process II. (1mk)
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- Between E and magnesium. (1mk)
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- Name: (1 ½ mks)
Process (I)………………………………………………………………………………………
Process (III)……………………………………………………………………………………….
Process (IV)………………………………………………………………………………………
- Give one distinguishing property of substance (½mk)
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- State two ways in which polymers K has improved human life. (2mks)
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- Study the flow chart below and use it to answer the questions that follow.
- Identify the anion and cation in solution K
Cation ………………………………………………………. (1mk)
Anion……………………………………………………. (1mk)
- Name the white precipitate (1mk)
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- Name the type of reaction in step 2. (1mk)
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- Name any other solution that would form white ppt T in step 3. (1mk)
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- Write the formula of the complex ion in solution (1mk)
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- Describe how a dry sample of the salt forming the white ppt T can be prepared in the laboratory starting with barium oxide.
(3mks)
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