Chemistry Paper 2 Questions and Answers - Mincks Group of Schools Mock Examinations 2022

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INSTRUCTIONS TO CANDIDATES

  • Write your name, class and admission number in the spaces provided above.
  • Answer all questions in the spaces provided.
  • This paper consists of Question 1 to 7
  • Students should check the question paper to ascertain that all the pages are printed as indicated and no questions are missing.

FOR EXAMINER’S USE ONLY

Question

Maximum Score

Candidate’s score

1

12

 

2

12

 

3

13

 

4

11

 

5

11

 

6

11

 

7

10

 

TOTAL

80

 

QUESTIONS

  1.                        
    1. Draw the structures of the following compounds. (2mks)
      1. 2-methylbut-2-ene
      2. Heptanoic acid
    2. Study the flow chart below and answer the questions that follow.
      b sfsfsfs
      1. Identify the organic compound K. (1mk)
      2. Write the formula of M. (1mk)
      3. Give one reagent that can be used in:
        Step I (1mk)
        ……………………………
        Step II (1mk)
        ……………………………
      4. Write the equation of the reaction in Step III. (1mk)
    3. Name the process that occurs in: (2mks)
      Step II
      ………………………………………………
      Step IV
      ……………………………………………...
    4. The structure below represents a type of cleansing agent
      d adadada
      Describe how the cleansing agent removes grease from a piece of cloth. (3mks)
  2. Below is part of the periodic table. The letters are not the actual symbols of the elements. Study it and answer the questions that follow.
    2 adadad
    1.                    
      1. State and explain the differences in the melting point of D and F. (2mks)
      2. Explain the difference in the atomic radii of G and N. (2mks)
      3. Select the element that is the strongest reducing agent. Explain. (2mks)
      4. Compare the nature of the aqueous solution of the oxide of C and that of L.
        Explain. (2mks)
    2. Study the table below and answer the questions that follows:

      Substance

      MP(k)

      BP (k)

      Electrical conductivity

       

       

       

      Solid

      Molten

      J

      365

      463

      NIL

      NIL

      K

      1323

      2773

      Good

      Good

      L

      1046

      1680

      NIL

      Good

      M

      2156

      2776

      NIL

      NIL

    3. Which of the substance J, K, L and M represents the following:
      1. Silicon (IV) Oxide (1mk)
      2. Barium Sulphate (1mk)
    4. In terms of structure and bonding, explain why Silicon (IV) Chloride (SiCl4) is a liquid at room temperature while Magnesium chloride (MgCl2) is a solid. (2mks)
  3.                        
    1.                    
      1. What is meant by the term ‘Enthalpy of formation’. (1mk)
      2. The enthalpies of combustion of Carbon, Methane and Hydrogen are indicated below:
        C(s) + O2(g) → CO2(g) ; ∆H = -393kJmol-1
        H2(g) + ½ O2(g) →  H2O(l) ; ∆H = -286kJmol-1
        Enthalpy of combustion of CH4 = -890kJ/mol.
        1. Draw an energy cycle diagram that links the enthalpy of formation of methane to enthalpies of combustion of carbon, hydrogen and methane. (2mks)
        2. Determine the enthalpy of formation of methane. (2mks)
    2. An experiment was carried out where different volumes of dilute hydrochloric acid and aqueous sodium hydroxide both at 25ºC were mixed and stirred with a thermometer. The highest temperature reached by each mixture was recorded in the table below.

      Volume of Hydrochloric acid (cm3)

      5

      10

      15

      20

      25

      30

      35

      40

      45

      Volume of sodium hydroxide (cm3)

      45

      40

      35

      30

      25

      20

      15

      10

      5

      Highest temperature of mixture (oC)

      27.2

      29.4

      31.6

      33.8

      33.6

      31.8

      30.0

      28.4

      26.6

      1. On the grid provided, plot a graph of highest temperature (vertical axis) against volume of hydrochloric acid (horizontal axis). (3mks)
        graph paper
      2. Using your graph, determine the
        1. Highest temperature reached. (½mk)
        2. Volume of acid and base reacting when highest temperature is reached. (1mk)
      3. Calculate the amount of heat liberated during the neutralization process. (Specific heat capacity 4.2Jg-1k- and the density of solution is 1.0g/cm3. (1½mks)
    3. The molar enthalpy of neutralization between hydrochloric acid and ammonia solution was found to be -52.2kJ/mol-, while that of hydrochloric acid and sodium hydroxide was -57kJmol-1. Explain the difference in these values. (2mks)
  4.                        
    1. What is meant by rate of reaction. (1mk)
    2. In the space provided sketch the diagram of a set-up that can be used to determine the rate of reaction between manganese (IV) oxide and hydrogen peroxide. (3mks)
    3. A state of equilibrium between dichromate ions is established as shown below:
      Cr2O72-(aq) + 2OH- ↔ 2CrO42-(aq) + 4H2O(l)
        Orange                            Yellow
      1. What is meant by dynamic equilibrium. (1mk)
      2. State and explain observation made, when a few drops of hydrochloric acid are added to the equilibrium mixture. (2mks)
    4. Some plants have seeds that contain vegetable oil.
      1. Describe how the oil can be obtained from the seeds. (3mks)
      2. Explain how it could be confirmed that the liquid obtained from the seeds in oil. (1mk)
  5. Use the standard electrode potential given below to answer the questions that follows:
    Half reaction                            Eθ volts
    Zn2+(aq) + 2e- → Zn(s)                 -0.76
    Pb2+(aq) + 2e- →  Pb(s)                -0.13
    Ag+(aq) + e-  →  Ag(s)                   +0.80
    Cu2+(aq) + 2e- →  Cu(s)              +0.34
    1.                      
      1. Choose a pair that will form a cell with the higher Eθ value. (1mk)
      2. Draw a diagram to represent the cell formed by the pair in (i) above (3mks)
      3. Give a cell representation for the cell in (I) above (1mk)
      4. State two functions of the salt – bridge. (2mk)
    2.                            
      1. Using a well labelled diagram, explain how an iron spoon can be electroplated with silver. (2mks)
      2. 2.34g of metal Q were deposited when a current of 4.0 amperes was passed through a salt of Q for 30 minutes. (RAM of Q = 65, 1 Faraday = 96,500C) calculate the amount of electricity in coulomb:
        1. Used to deposit 2.34g of metal Q. (1mk)
        2. Needed to deposit one mole of Q. (1mk)
  6.                              
    1. Two reagents that can be used to prepare chlorine gas are Manganese (IV) oxide and concentrated hydrochloric acid.
      1. Write an equation for reaction. (1mk)
      2. Give the formula of another reagent that can be reacted with concentrated hydrochloric acid to produce chlorine gas. (1mk)
      3. Describe how the chlorine gas would be dried in the laboratory. (2mks)
    2. In an experiment, dry chlorine gas was reacted with aluminium as shown in figure below
      6b afafaf
      1. Name substance A. (1mk)
      2. Write an equation for the reaction that took place in the combustion tube. (1mk)
      3. 0.84g of aluminium reacted completely with chlorine gas. Calculate the volume of chlorine gas used (Molar gas volume is 24dm3 Al=27) (3mks)
      4. Give two reasons why Calcium oxide is used in the set up. (2mks)
  7. Extraction of iron involves two main processes, smelting and refining. Below is the blast furnace which is used to smelt iron from its ore.
    7 adadada
    1.                            
      1. The chief ore is Hamematite. Name one other ore used in extraction iron. (1mk)
      2. Name the reducing agent in the process. (1mk)
      3. What is the role of the hot air blast in the process. (1mk)
    2. Write equations for the reaction that took place of the region marked A, B and C. (3mks)
      A ………………………………………………………………………………….
      B ………………………………………………………………………………….
      C ………………………………………………………………………………….
    3. What is the purpose of limestone in the extraction process. (1mk)
    4. Write equations to show how impurities are removed from the ore. (2mks)
    5. State one environmental effect of the process. (1mk)

MARKING SCHEME

  1.                      
    1.                      
      1.            
        1 i adaddada
      2.               
        1 ii sfsfsf
        Accept open structural formula.
        CH3 may or may not be open.
        OH may or may not be open.
    2.                      
      1. Ethane/ C2 H6 
        1 b i adadadad
      2. C3 H6 Cl2 
        1 b ii sddada
      3.                
        1. Water/ steam/ conc. H2 SO4 1mrk
        2. Acidified KMnO4 /KMnO4/Acidified K2 Cr2 O7 Any 1mrk
      4. 2CH3 CH2 CH2 OH + 2Na → 2CH3 CH2 CH2 ONa + H2 1 mrk
        Ignore missing or wrong state symbols.
        Penalize fully if not balanced.
    3.                          
      1. Oxidation 1mrk
      2. Decarboxylation 1mrk
    4. Cleansing agent has polar end ½ and non – polar end ½ Non – polar end attracts ½ Grease while polar end attracts water molecules ½ This lower the surface tension of water/ emulsification of grease ½
  2.                      
    1.                      
      1. D has a lower melting point than F ½ because F has more valence electrons ½ and smaller atomic radius hence stronger metallic bonds which require a lot of energy to break.
      2. G has a larger atomic radius than N. N has more protons than G/ N has a greater nuclear attraction than G./ N has a more effective nuclear charge than G.
      3. D 1mrk; Has the largest atomic radius / thus loses it’s outermost electrons most readily.
      4. Oxide of L is acidic ½ while that of C is basic/alkaline1/2 Oxide of L dissolves in water to form H+ ions ½ while that of C dissolves in water to form OH- ions ½
    2.                    
      1. M 1mrk
      2. L 1mrk
    3. In SiCl4 molecules are joined together by weak van der waals forces ½ . Forming a simple molecular structure while in Mg Cl2 ions are linked by strong ionic bonds / electrostatic forces of attraction ½ forming giant ionic structure ½
  3.                          
    1.                          
      1. Heat change that occurs when one mole of a substances is formed from its constituent elements ( in their normal State) 1mrk
        Or
        Heat absorbed or evolved when one mole of a substance is formed from its constituent elements in their normal states.
      2.                              

        1. 3 a afafafa
          Equation for CH4 formation ½
          Equation for CO2 and H2O combustion 1mrk
          Equation for CH4 combustion 1/2mrk Total= 2mrks
        2. Δhf = ΔH2 – ΔH1
          = -393+ 2(-286) + 890
          =-75kJMol-1

          Penalize ½ for wrong or missing units.
    2.                          
      1. Plotting
        9 correct plots 1
        8 correct plots ½
        < 8 correct plots 0
        Scale
        Horizontal scale – ½
        Vertical scale ½
        Line Extrapolation ½
        Inverted ½
      2.                      
        1. Value read from graph = ½
        2. Acid volume from graph ½
          Base volume = 50cm3 acid volume from graph ½
      3. ΔT value (Final Temp from graph -25ºC) ½
    3. NH3 is a weak base hence some of the heat evolved is used to completely ionize NH3(aq)
  4.                    
    1. measure of how much of the reactants are consumed or how much products are formed per unit time.
    2.                            
      4 b adadada
    3.                  
      1. Reaction in which rate of forward reaction is equal to the rate of reverse/ backward reaction. 1mrk
      2.                            
    4.                            
      1. Crush(1mrk) the seeds using a mortal and pestle, add suitable solvent such as propanone / acetone/ ethanol/ propanol ½ and continue crushing. The liquid is filtered / decanted/sieved ½ in an evaporating dish. The dish is placed out into the sun to allow the solvent to evaporate leaving the oil behind. ½
      2. The liquid left after evaporation is placed on apiece of paper. If it leaves a translucent mark then it approves it is oil.
  5.                                
    1.                        
      1. Ag/Ag+(aq) and Zn(s)/Zn2+(aq) Or 1mrk
        Zn/Zn2+(aq) // Ag+(aq)/Ag(s) 1mrk
        Or
        Zn and Ag half cells.
      2.                 
        5 a ii adadad
      3. Zn(s)/Zn2+(aq)//Ag+(aq)/Ag(s) 1mrk
      4. Completes the circuit 1mrk
        Maintains charge balance 1mrk
        Replenishes the used ions in the two half cells
    2.                   
      1. 5 b adafaf
        Workability ½
        1. Q = It
          = 4 x 30 x 60 ½
          = 7200C ½ Penalize if missing units.
        2. 2.34g → 7200C
          65g  → ?
          = 65g x 7200C ½
                   2.34g
          =200 000C ½
  6.              
    1.                                                
      1. MnO2(s)+ 4HCl(aq) → MnCl2(aq) + Cl2(g) + 2H2 O(l) 1mrk
      2. KMnO4(s)/ Pb O2(s) / CaOCl2(s)
      3. By passing Cl2(g) through a U – tube containing anhydrous CaCl2
        Drying agent 1mrk
        Suitable Apparatus 1mrk
        By passing Cl2(q) through concentrated H2 SO4 in a flask or bulling tube.
        Or
        6 adadad
    2.                  
      1. Aluminum chloride/Al Cl3
      2. 2Al(s) + 3Cl(s) → 2AlCl3(g)/ Al2 Cl6(g)
      3. Mol Al used = 0.84 = 0.0311 1 mrk
                               27
        Mol of Cl2 = 0.0311x 3 = 0.047 1 mrk
                                  2
        Volume of Cl2 = 0.047 x 24 = 1.12 dm3
        Or
        0.84 x 3 x 24 = 1.12dm3 3mks
        27
        This part is consequential to part iii)
        If more raha not used give a maximum of 2mrks
      4. Prevent moisture from entering its apparatus by absorbing it/ prevent hydrolysis of AlCl2
        To react with excess Cl2 / preventing environmental pollution by Cl2.
  7.                          
    1.             
      1. Magnetite/ Siderite 1 mrk
      2. Carbon (ii) oxide 1mrk
      3. React with coke/charcoal / carbon to form carbon (iv) Oxide
        Rise the temperature at the bottom of the finance to about 200K (165ºC)
    2. A; C(s)+O2 (g) →  CO2(g) 1mrk
      B; Fe2 O3(s) + 3CO(g) →  2Fe(s) + CO2(s) 1mrk
      C; CaCo3(s) →  CaO(s) + CO2(g) 1mrk
    3. Decompose to quick lime (calcium oxide) which react to remove impurities and produce more carbon (iv) oxide gas.
    4. CaO + Si O2(s) → Ca Si O3(s) 1mrk
      CaO + Al2 O3(s) → Ca Al2 O4(s) 1mrk
    5. Carbon (iv) Oxide gas causes global warming if allowed to escape. 1mrk
      Carbon (iv) Oxide is highly poisonous/ toxic that can kill.
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