Chemistry Paper 2 Questions - Mokasa II Joint Mock Exams 2023

Instructions to students:

Answer all questions
Candidates must answer all questions in English

1. Use the standard reduction potentials given below to answer the questions that follow.
  Half –cell reactions E^θ(V)
  B²⁺_(aq) + 2e⁻ B_(S) −0.44
  A²⁺_(aq) + 2e⁻ A_(S) −0.76
  C_2(aq) + 2e⁻ 2C⁻_(S) +0.54
  2E⁺_(aq) + 2e⁻ B_(S) 0.00
  D³⁺_(aq) + 3e⁻ D_(S) −1.66
  1. Identify the strongest oxidizing agent. Give a reason. (1mk)
  2. Arrange the elements having the negative standard reduction potentials in order of increasing reactivity. (2mks)
  3. Calculate the e.m.f of a cell formed by combing the half-cells of B and D. (2mks)
  4. Write down the overall equation for the reaction taking place in (iii) above. (1mk)
  5. Draw an electrochemical cell represented by the cell notation A_(s) / A²⁺_(aq) // B²⁺/B(S). (3mks)
  6. Draw a well – labeled diagram to showing how a spoon made of D is electroplated using A. (3mks)
2. Determine the oxidation state of Mn in MnO4- (1mk)
Study the flow chart below for the extraction of aluminum from ore.
1. Name the chief ore from which aluminium is extracted. (½ mk)
2. Give two impurities present in the ore. (1mk)
3. Briefly explain how the impurities in (ii) above are removed. (2mks)
4. Identify: (1mk)
  1. Solution F…………………………………………………………………………………….
  2. Residue S…………………………………………………………………………………….
5. Write balance equations for
  1. The reaction taking place in process X (1mk)
  2. Reaction producing gas F (1mk)
6. State any one uses of aluminium (½ mk)
7. Compare the atomic radius of aluminium with that of sodium. (Al = 13, Na = 11). (2mks)
8. 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)
1. 1. Define the term “Dynamic Equilibrium”. (1mk)
  2. List two factors, other than concentration, that affects chemical equilibrium. (1mk)
  3. Explain the importance of the factors mentioned above to an industrialist. (1mk)
  4. Consider the reaction below an equilibrium .
    Br_2(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)
2. 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.
  1. Why is the process referred to as Contact Process? (½mk)
  2. Identify (2mks)
    1. Solid C………………………………………………………………………………………..
    2. Gas M…………………………………………………………………………………………
    3. Gas L………………………………………………………………………………………….
    4. Liquid V ……………………………………………………………………………………...
  3. Write down the equation for the reaction taking place in the absorption tower. (1mk)
  4. Other than recycling, describe how pollution can be minimized in the process. (1mk)
  5. 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 Kg. (2 ½mks)
    (MGV= 24 L)
1. In an experiment to determine the heat of methanol, a student set-up the apparatus as shown below. Study the set-up and use the data obtained to answer the questions that follow.
  
  Initial temperature of water = 22ºC
  Finial temperature of water = 36ºC
  Initial mass of lamp + methanol = 85.10 g
  Final mass of lamp + methanol = 84.75 g
  Density of water = 1g/cm³ C = 4.2 Jg^-1k^-1
  1. Determine the heat change for this experiment. (1mk)
  2. Determine the molar enthalpy of combustion of methanol. (2mks)
  3. Write down a thermochemical equation for the reaction. (1mk)
  4. Draw an energy level diagram for the reaction. (2mks)
  5. The molar enthalpy of combustion of thane (C₂H₆) is -1560 kJmol^-1. Explain which one is a better fuel between methanol and ethane.
    (C= 12, O = 16, H = 1) (2mks)
2. Use the information below to answer the question that follow
  Ca_(s) + ½ O_2(g) → CaO_(s) ∆H₁ = - 635kJmol^-1
  C_(s) + O_2(g) → CO_2(g) ∆H₂ = -394kJmol^-1
  Ca_(s) + C_(s) + ³/₂O_2(g) → CaCO_3(S) ∆H₃ = - 207kJmol^-1
  1. Name two enthalpy changes represented by ∆H2 (2mks)
  2. Use the information above to calculate the enthalpy change for the reaction (3mks)
    CaO_(s) + CO_2(g) → CaCO_3(s)
1. Study the set-up below and use it to answer the questions that follow.
  1. State the observation made in the combustion tube. (1mk)
  2. Write an equation for the reaction producing the flame. (1mk)
  3. Explain the observation made in the conical flask when the experiment is done for a longer period of time (2mks)
2. The flow chart below show the manufacture of sodium carbonate. Study it carefully and answer the questions that follow.
  1. Identify (1 ½ mks)
    1. Gas X……………………………………………
    2. Gas Y…………………………………………….
    3. Liquid Q …………………………………………
  2. Give one use of calcium chloride. (½ mk)
  3. Write balanced chemical equations for the reactions in (2mks)
    1. Chamber III
    2. Chamber IV
  4. Give two reasons why the Solvay process is considered one of the most efficient industrial process? (2mks)
  5. Name two process taking place in chamber II. (1mk)
Study the flow chart below and use it to answer the questions that follow.
1. Give the names of substances (2mks)
  1. N…………………………………………………………………………………………………..
  2. F…………………………………………………………………………………………………..
  3. A………………………………………………………………………………………………….
  4. E…………………………………………………………………………………………………..
2. Give the conditions necessary for: (1 ½mks)
  1. Process I
  2. Process IV ( ½mk)
3. Draw the open structural formula of B. (1mk)
4. Write balanced chemical equations for the reaction in
  1. Process II. (1mk)
  2. Between E and magnesium. (1mk)
5. Name: (1 ½ mks)
  1. Process (I)………………………………………………………………………………………
  2. Process (III)……………………………………………………………………………………….
  3. Process (IV)………………………………………………………………………………………
6. Give one distinguishing property of substance B. (½mk)
7. State two ways in which polymers K has improved human life. (2mks)
Study the flow chart below and use it to answer the questions that follow.
1. Identify the anion and cation in solution K
2. Name the white precipitate L. (1mk)
3. Name the type of reaction in step 2. (1mk)
4. Name any other solution that would form white ppt T in step 3. (1mk)
5. Write the formula of the complex ion in solution M. (1mk)
6. Describe how a dry sample of the salt forming the white ppt T can be prepared in the laboratory starting with barium oxide. (3mks)