Chemistry Paper 1 Questions and Answers - Kassu Joint Mock Examination 2021

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Instructions to Candidates

  1. Write your name and index number in the spaces provided above.
  2. Sign and write the date of examination in the spaces provided above
  3. Answer ALL the questions in the spaces provided in the question paper
  4. KNEC Mathematical tables and electronic calculators may be used for calculations
  5. All working MUST be clearly shown where necessary
  6. This paper consists of 12 printed pages
  7. Candidates should check the question paper to ascertain that all the pages are printed as indicated and that no questions are missing
  8. Candidates should answer the questions in English

QUESTIONS

  1. Study the diagram below then use it to answer the questions that follow.
    1
    1. Draw the wooden splint at the end of the experiment. If it was slipped then removed. (1 mark)
    2. Explain the appearance of the wooden splint in (a) above. (2 marks)
      ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………
  2.      
    1. The half-life of M is 7 days. Determine the mass of remaining if 100g decayed in 35 days. (1 mark)
      ………………………………………………………………………………………………………………………………………………………………………………………………………………………………
    2. The diagram below shows the radiations emitted by a radioactive sample.
      2
      1. Identify radiation particles S and R. (1 mark)
        S……………………………………………………
        R……………………………………………………
      2. Which emission causes most harm to human cells. Give a reason. (1mark)
        ………………………………………………………………………………………………………………………………………………………………………………………………………………………………
  3. Starting with copper metal, describe how a solid sample of copper (II) carbonate can be prepared. (3 marks
    ……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………
  4. The set-up below was used to obtain a sample of iron.
    3
    Write two equations for the reactions which occur in the combustion tube. (2 marks)
    ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………
  5. Below are the bond dissociation energies of some elements.
    Bond Bond dissociation energy
    C – C  343 kJ mol-1 
    C – H  414 kJ mol-1 
    H – H  435 kJ mol-1 
    C = C  612 kJ mol-1 
    Use this information to calculate the heat of reaction for (3 marks)
    C2H4(g)+H2(g) → C2H6(g)
  6. Sulphur (IV) oxide is oxidized catalytically to sulphur (VI) oxide in the reaction.
    2SO2(g)+O2(g)2SO3(g) ΔH=-197kJ
    1. What information about the reaction is given by ∆H = -197kJ ? (1 mark)
      ………………………………………………………………………………………………………………
    2. Name one catalyst that can be used in this reaction. (1 mark)
      ………………………………………………………………………………………………………………
  7. Study the scheme below and answer the questions that follow.
    4
    1. Write the formula of the cation present in solution D. (1 mark)
      ………………………………………………………………………………………………………………
    2. What property of chlorine is shown in step 1. (1 mark)
      ………………………………………………………………………………………………………………
    3. Write an equation for the reaction which occurred in step III. (1 mark)
      ………………………………………………………………………………………………………………
  8. 0.63g of lead powder were dissolved in excess nitric (V) acid to form lead (II) nitrate solution. All the lead (II) nitrate was then reacted with sodium sulphate solution.
    1. Write an ionic equation for the reaction between sodium sulphate solution and lead (II) nitrate solution. (1 mark)
      ………………..………………………………………………………………………………………..……
    2. Determine the mass of the lead salt formed in the reaction in (a) above (Pb = 207, S = 32, O = 16) (2 marks)
      ………………..…………………
  9. Use the cell representation below to answer the questions that follow.
    Cr(s)/Cr3+(aq)//Fe2+(aq)/Fe(s)
    1. Write an equation for the cell reaction. (1 mark)
      ………………………………………………………………………………………………………………
    2. If the emf of the cell is 0.30V and the Eº value for Fe2+ / Fe(S) is -0.44V. Calculate the Eº value for Cr(s) / Cr3+(aq) (2 marks)
  10. An element Q has a relative atomic mass of 88. When a current of 0.5A was passed through the fused chloride of Q for 32 minutes and 10 seconds, 0.44g of Q were deposited at cathode. Determine the charge on the ion of Q. (1 Faraday = 96500 coulombs) (3 marks)
  11. The table below gives three experiments on the reaction of excess sulphuric (VI) acid and 0.5g Zinc done under different conditions. In each case the volume of gas liberated was recorded at different time intervals.
    Experiment Form of Zinc Sulphuric (VI) acid
    I
    II
    III 
    Powder
    Powder
    Granules
    0.8M
    1.0M
    0.8M
    On the axes below, draw and label the three curves that would be obtained from the results above.(3 marks)
    5
  12.    
    1. Starting with red roses, describe how a solution containing the red pigments may be prepared? (2 marks)
      ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………
    2. How can the solution be shown to be an indicator. (1 mark)
      ………………………………………………………………………………………………………………
  13. The table below provides data on the successive ionisation energies of carbon.
    Ionisation numbers 1st 2nd 3rd 4th 5th 6th
    Ionisation energy (kJ/mol) 1090 2350 4610 6220 37800 47300
    1. Explain why each ionisation energy increase in nature. (2 marks)
      ………………………………………………………………………………………………………………………………………………………………………………………
    2. Write an equation for the 5th ionisation energy of carbon. (1 mark)
      …………………………………………………………………………………………………………
  14. The figure below was set by a student to investigate the reaction between chlorine gas and hydrogen sulphide gas.
    6
    1. Write an equation for the reaction that took place in the flask. (1 mark)
      …………………………………………………………………………………………………………………………………………………………………………………………………………
    2. What observation was made in the flask ? (1 mark)
      ………………………………………………………………………………………………………………
    3. What precaution should be taken in carrying out the experiment ? (1 mark)
      ………………………………………………………………………………………………………………………………………………………………………………………………………
  15. A certain carbonate, QCO3, reacts with dilute hydrochloric acid according to the equation given below.
    If 1g of the carbonate reacts completely with 20cm³ of 1M hydrochloric acid. Calculate the relative atomic mass of Q.(C = 12.0, O=16.0) (3 marks)
  16. When bismuth (III) chloride is added to water, a reaction occurs and a white precipitate forms as shown below.
    BiCl3(aq) + H2O(l) → BiOCl(s) + 2HCl(aq)
    What would be the effect on the amount of the precipitate formed if sodium hydroxide solution is added to the equilibrium mixture? Explain your answer. (2marks)
    ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………
  17.      
    1. State the Gay Lussac's Law. (1 mark)
      ……………………………………………………………………………………………………………………………………………………………………………………………………………………
    2. 10cm3 of a gaseous hydrocarbon, C2HX required 30cm3 of oxygen for complete combustion. If steam and 20cm3 of carbon (IV) oxide were produced, what is the value of X? (2 marks)
  18.      
    1. Give Bronsted and Lowry definition of an acid (1mk)
      ………………………………………………………………………………………………………………
      ……………………………………………………………………………………………………………….
    2. Differentiate between a strong acid and a concentrated acid (2mks)
      ………………………………………………………………………………………………………………
      ………………………………………………………………………………………………………………
      ………………………………………………………………………………………………………………
  19. When a hydrated sample of CaSO4.xH2O was heated until all water was lost, the following data was recorded
    Mass of crucible = 30.296 g
    Mass of crucible + hydrated salt = 33.111 g
    Mass of crucible + anhydrous salt = 32.781 g
    Determine the empirical formula of the hydrated salt. (CaSO4=136,H2O=18). (3marks) .……………………………………………………………………………………………………………………………………………………………………………………………………………………..………………………………………………………………………………………………………………………………………………………………………………………………………
  20. Describe a chemical test used to distinguish butane from butene in the laboratory. (2marks)
    .………………………………………………………………………………………………………………
    …………………………………………………………………………………………………………………………………………………………………………………….………………………………
  21. The table below gives the atomic numbers of elements W, X, Y and Z.
    Element W X Y Z
    Atomic number 14  17 16 19
    1. Name the type of bonding that exist in the compound formed when X and Z reacts. (1mark)
      .………………………………………………………………………………………………………………………………………………………………………………………………………………
    2. Select the letter representing the strongest reducing agent. Give a reason for your answer. (2mks)
      .………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………
  22. In an electrochemical cell, the standard hydrogen electrode uses platinized platinum. State three functions of the platinized platinum. (3 marks)
    ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………
  23. The flowchart below shows the scheme for extraction of Hydrogen from hydrolysis of natural gas, study it and answer the questions that follow.
    7
    1. In step II water gas is formed. State one use of water gas. (1marks)
      ……………………………………………………….…………………………………………
    2. When air is added in step III CO is converted to CO2 name one chemical substance that can be used to separate CO2 from H2 in step IV (1marks)
      ……………………………………………………………………………………………………
    3. State one large scale use of Hydrogen gas formed. (1marks)
      …………………………………………………………………………..…………………………
  24. Aluminium is obtained from the ore with the formula Al2O3. 2H2O. The ore is first heated and refined to obtain pure aluminium oxide (Al2O3). The oxide is then electrolysed to get Aluminium and oxygen gas using carbon anodes and carbon as cathode.
    1. Give the common name of the ore from which aluminium is extracted. (1 mark)
    2. What would be the importance of heating the ore first before refining it ? (1 mark)
      .........................................................................................................................................................................
    3. The refined ore has to be dissolved in cryolite first before electrolysis. Why is this necessary? ……………………………………………………………………………………………. (1 mark)
    4. Why are the carbon anodes replaced every now and then in the cell for electrolysing aluminium oxide? (1 mark)
      ................................................................................................................................................................................................................................................................................................................................................
  25. Nylon polymer has the structure below.
    8
    1. Determine the structures of the monomers. (2mks)
      ……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………..………………………………………………………………………………………
    2. State the type of polymerization. (1mk)
      ……………………………………………………………………………………………………………..… ………………………………………………………………………………………………………..
  26.    
    1. Define the term solubility. (1 mark) …………………………………………………………………………………………………………………………………………………………………………………………………
    2. The following were the results obtained in an experiment to determine solubility of potassium
      nitrate at room temperature.
      Mass of evaporating dish = 14.32 g
      Mass of evaporating dish + saturated solution = 35.70 g
      Mass of evaporating dish + salt (residue) = 18.60 g
      Calculate the solubility of potassium nitrate from the above results. (2 marks) ……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………...........................................…………………………………………………………………………………………..…
  27. Describe a simple laboratory experiment that can be used to distinguish between sodium sulphide and sodium carbonate. (2mks)
    ……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………...........................................…………………………………………………………………………………………..…
  28.      
    1. Give one reason some of the laboratory apparatus are made of ceramics.(1 mark)
      ……..........................………………………………………………………………………………………….
    2. Name two apparatus that can be used to measure approximately 75 cm3 of dilute sulphuric (VI) acid. (2 marks)
      …………………………………………………………………………………………………………………………………….


 



 



 



 



 



 



 



 



 



MARKING SCHEME

QUESTIONS

  1. Study the diagram below then use it to answer the questions that follow.
    1
    1. Draw the wooden splint at the end of the experiment. If it was slipped then removed. (1 mark)
      1
    2. Explain the appearance of the wooden splint in (a) above. (2 marks)
      Charred part is the hottest zone as a result complete combustion of gases while uncharred zone is as a result of incomplete combustion of gases
  2.      
    1. The half-life of M is 7 days. Determine the mass of remaining if 100g decayed in 35 days. (1 mark)
      No of half lives = 35/7 = 5 half lives
      R=(½)n x original mass = 1/32 x 100
      R = (1/3)5x100 = 3.125g
      R = 3.125
    2. The diagram below shows the radiations emitted by a radioactive sample.
      2
      1. Identify radiation particles S and R. (1 mark)
        S - Beta Particles
        R - Alpha particles
      2. Which emission causes most harm to human cells. Give a reason. (1mark)
        Alpha has greater effect
  3. Starting with copper metal, describe how a solid sample of copper (II) carbonate can be prepared. (3 marks
    • Heat copper metal in air obtain copper oxide
    • React CuO with dilute HNO3 to obtain Cu(NO3)2 solution
    • Filter to obtain Cu(NO3)2 as filter and unreacted CuO as resedue
    • React Cu(NO3)2 with Na2CO3 to obtain CuCO3 and NaNO
    • Filter to obtain Cu(NO3)2 resecue and NaNOas filtrate
    • Dry between the filter papers to get CuCO3
  4. The set-up below was used to obtain a sample of iron.
    3
    Write two equations for the reactions which occur in the combustion tube. (2 marks)
    2C + O2 → 2CO(g) 
    Fe O3 + 3CO(g) → 2Fe + 3CO
  5. Below are the bond dissociation energies of some elements.
    Bond Bond dissociation energy
    C – C  343 kJ mol-1 
    C – H  414 kJ mol-1 
    H – H  435 kJ mol-1 
    C = C  612 kJ mol-1 
    Use this information to calculate the heat of reaction for (3 marks)
    C2H4(g)+H2(g) → C2H6(g) 
    2
  6. Sulphur (IV) oxide is oxidized catalytically to sulphur (VI) oxide in the reaction.
    2SO2(g)+O2(g)2SO3(g) ΔH=-197kJ
    1. What information about the reaction is given by ∆H = -197kJ ? (1 mark)
      Endothermic reaction
    2. Name one catalyst that can be used in this reaction. (1 mark)
      Vanadium oxide (reject V2O5)
  7. Study the scheme below and answer the questions that follow.
    4
    1. Write the formula of the cation present in solution D. (1 mark)
      Fe2(SO4)3
    2. What property of chlorine is shown in step 1. (1 mark)
      Oxidising agent
    3. Write an equation for the reaction which occurred in step III. (1 mark)
      2[e(OH)]3 →fe2O3P3H2O
  8. 0.63g of lead powder were dissolved in excess nitric (V) acid to form lead (II) nitrate solution. All the lead (II) nitrate was then reacted with sodium sulphate solution.
    1. Write an ionic equation for the reaction between sodium sulphate solution and lead (II) nitrate solution. (1 mark)
      Pb2+ + SOPbSO4
    2. Determine the mass of the lead salt formed in the reaction in (a) above (Pb = 207, S = 32, O = 16) (2 marks)
      Moles of Pb = 0.63
                           207
      M.R = 1:1
      Moles of PbSO4 = 0.00304
      Mass = 0.00304 x 303 = 0.92112
  9. Use the cell representation below to answer the questions that follow.
    Cr(s)/Cr3+(aq)//Fe2+(aq)/Fe(s)
    1. Write an equation for the cell reaction. (1 mark)
      Fe2+ + Cr → Cr3+ + Fe
    2. If the emf of the cell is 0.30V and the Eº value for Fe2+ / Fe(S) is -0.44V. Calculate the Eº value for Cr(s) / Cr3+(aq) (2 marks)
      Eº = Eºred - Eºoxi
      0.30v = -0.44 - Eºoxi 
      cr/cr 3p = -0.44 - 0.30
      = -0.74V
  10. An element Q has a relative atomic mass of 88. When a current of 0.5A was passed through the fused chloride of Q for 32 minutes and 10 seconds, 0.44g of Q were deposited at cathode. Determine the charge on the ion of Q. (1 Faraday = 96500 coulombs) (3 marks)
    MASS = MIT
                 ZF
    0.44g =88x0.5x1930
                  Z x 96500
    0.44= 0.88
                Z
    0.44 Z
    =0.88
    0.44      0.44
    Z = +2
    Q2+ 
    Alternatively 
    Q = 1t
    =0.55 x 1930
    =9656
    0.44 = 965
    88 x 965
    =193000
       0.44        96500
  11. The table below gives three experiments on the reaction of excess sulphuric (VI) acid and 0.5g Zinc done under different conditions. In each case the volume of gas liberated was recorded at different time intervals.
    Experiment Form of Zinc Sulphuric (VI) acid
    I
    II
    III 
    Powder
    Powder
    Granules
    0.8M
    1.0M
    0.8M
    On the axes below, draw and label the three curves that would be obtained from the results above.(3 marks)
    3
  12.    
    1. Starting with red roses, describe how a solution containing the red pigments may be prepared? (2 marks)
      • Crush roses using pestle and Mortar
      • Add propane to dissolve the red pigments
      • Filter to obtain red pigment solution as filtrate
    2. How can the solution be shown to be an indicator. (1 mark)
      Add drops of the pigment to different types of acids or bases. It will show some color on acids and different but same color on bases
  13. The table below provides data on the successive ionisation energies of carbon.
    Ionisation numbers 1st 2nd 3rd 4th 5th 6th
    Ionisation energy (kJ/mol) 1090 2350 4610 6220 37800 47300
    1. Explain why each ionisation energy increase in nature. (2 marks)
      After the removal of an electron, the overall nuclear charge hold the remaining electrons firmly
    2. Write an equation for the 5th ionisation energy of carbon. (1 mark)

  14. The figure below was set by a student to investigate the reaction between chlorine gas and hydrogen sulphide gas.
    6
    1. Write an equation for the reaction that took place in the flask. (1 mark)
      H2S + Cl → S + 2HCl
    2. What observation was made in the flask ? (1 mark)
      Yellow depecits of sulphur is formed
  15. A certain carbonate, QCO3, reacts with dilute hydrochloric acid according to the equation given below.
    If 1g of the carbonate reacts completely with 20cm³ of 1M hydrochloric acid. Calculate the relative atomic mass of Q.(C = 12.0, O=16.0) (3 marks) 
    1 mole = 1000cm3
    20 x 1 = 0.02 moles
     1000
    Mole ratio QCO3:HC1
    1:2
    Moles of QCO3=0.02=0.01moles
                             2
    RFM =Mass
              RFM
    =   1   = 100
       0.01
    100=Q + 12 + 48
    100= Q + 60
    Q = 40
  16. When bismuth (III) chloride is added to water, a reaction occurs and a white precipitate forms as shown below.
    BiCl3(aq) + H2O(l) → BiOCl(s) + 2HCl(aq)
    What would be the effect on the amount of the precipitate formed if sodium hydroxide solution is added to the equilibrium mixture? Explain your answer. (2marks)
    White precipitate increases intensities; when Hyhdroxide is intriduced it reacts with H+ from the HCl hence system shift from left to right
  17.      
    1. State the Gay Lussac's Law. (1 mark)
      When gases react, they do so in volumes that bear a simple whole number ratio to one other and to that y products if gaseous at constant temperature and pressure 
    2. 10cm3 of a gaseous hydrocarbon, C2Hx required 30cm3 of oxygen for complete combustion. If steam and 20cm3 of carbon (IV) oxide were produced, what is the value of X? (2 marks)
      C2Hx + 3O2 → 2CO2 + 2H2O
  18.      
    1. Give Bronsted and Lowry definition of an acid (1mk)
      An acid in a proton donor
    2. Differentiate between a strong acid and a concentrated acid (2mks)
      Strong acid is type of acid that dessociate fully into it ions while concentrated acid is an acid that has mor H+ ions
  19. When a hydrated sample of CaSO4.xH2O was heated until all water was lost, the following data was recorded
    Mass of crucible = 30.296 g
    Mass of crucible + hydrated salt = 33.111 g
    Mass of crucible + anhydrous salt = 32.781 g
    Determine the empirical formula of the hydrated salt. (CaSO4=136,H2O=18). (3marks)
    Compound CuSO4 H2O
    Mass
    RFM
    No of moles
    Mole ratio
    2.485
    136
    0.01827
    0.618271
    0.33
    18
    0.0183
    0.01827
    CuSO4.H2O
  20. Describe a chemical test used to distinguish butane from butene in the laboratory. (2marks)
    • Add bromine water to butane and Butene in different test tubes
    • Testtube containing butene will decolorise bromine water while butane does not
  21. The table below gives the atomic numbers of elements W, X, Y and Z.
    Element W X Y Z
    Atomic number 14  17 16 19
    1. Name the type of bonding that exist in the compound formed when X and Z reacts. (1mark)
      Ionic
    2. Select the letter representing the strongest reducing agent. Give a reason for your answer. (2mks)
      Z has the largest atomic radius 
  22. In an electrochemical cell, the standard hydrogen electrode uses platinized platinum. State three functions of the platinized platinum. (3 marks)
    • Acts as an input metal collection to the H2H+ system 
    • Provides a surface area on which dissociation of H2 molecules take place
    • Serves as an electrical conductor to the external circuit
  23. The flowchart below shows the scheme for extraction of Hydrogen from hydrolysis of natural gas, study it and answer the questions that follow.
    7
    1. In step II water gas is formed. State one use of water gas. (1marks)
      In fuel in cells
    2. When air is added in step III CO is converted to CO2 name one chemical substance that can be used to separate CO2 from H2 in step IV (1marks)
      Calcium Hydroxide
    3. State one large scale use of Hydrogen gas formed. (1marks)
      Any correct
  24. Aluminium is obtained from the ore with the formula Al2O3. 2H2O. The ore is first heated and refined to obtain pure aluminium oxide (Al2O3). The oxide is then electrolysed to get Aluminium and oxygen gas using carbon anodes and carbon as cathode.
    1. Give the common name of the ore from which aluminium is extracted. (1 mark)
      Bauxite
    2. What would be the importance of heating the ore first before refining it ? (1 mark)

    3. The refined ore has to be dissolved in cryolite first before electrolysis. Why is this necessary?(1 mark)
      To issue the melting point
    4. Why are the carbon anodes replaced every now and then in the cell for electrolysing aluminium oxide? (1 mark)
      They are eaten away due to reacting with oxygen under high temperature
  25. Nylon polymer has the structure below.
    8
    1. Determine the structures of the monomers. (2mks)
      4
    2. State the type of polymerization. (1mk)
      Condensation
  26.    
    1. Define the term solubility. (1 mark)
      The maximum amount of solute that can soluate 100g of solvent at a particular temperature
    2. The following were the results obtained in an experiment to determine solubility of potassium
      nitrate at room temperature.
      Mass of evaporating dish = 14.32 g
      Mass of evaporating dish + saturated solution = 35.70 g
      Mass of evaporating dish + salt (residue) = 18.60 g
      Calculate the solubility of potassium nitrate from the above results. (2 marks) 
      Mass of solute = 18.60 - 14.32 = 4.28g
      Massof solvent = 35.70 - 18.60 = 17.1g
      4.28g = 17.1g of colvent 
      100g of colvent x 4.28g = 25.03g / 100g of solvent
  27. Describe a simple laboratory experiment that can be used to distinguish between sodium sulphide and sodium carbonate. (2mks)
    • React with acid separately    
    • Test the gas produced using audities K2Cr2O7
    • Sulphide produces gas that turns orange audities K2Cr2Ogreen white for carbonate it remains orange 
  28.        
    1. Give one reason some of the laboratory apparatus are made of ceramics.(1 mark)
      Can withstand strong heating
    2. Name two apparatus that can be used to measure approximately 75 cm3 of dilute sulphuric (VI) acid. (2 marks)
      100cm3 measuring cylinder
      100cmbeaker

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