Chemistry Paper 1 Questions and Answers - Momaliche Joint Mock Exams 2021/2022

INSTRUCTIONS TO CANDIDATES

• Write your name and admission number in the spaces provided above
• Sign and write the date of examination in the spaces provided.
• Answer allthe questions in the spaces provided.
• Mathematical table and silent electronic calculators may be used.
• All working must be clearly shown where necessary.

1. The apparatus shown below was used to investigate the effect of carbon(II) oxide on copper(II)oxide.
   
   
   1. State the observation that was made in the combustion tube by the end of the experiment. (1 mark)
   2. Write an equation for the reaction that took place in the combustion tube. (1mark)
   3. Why is it necessary to burn gas coming out of tubeK? (1mark)
2. Name the process which takes place when:
   
   1. Iodine changes directly from solid to gas (1mk)
   2. The process of hardening rubber by heating it together with sulphur(1mk)
   3. White sugar changes to black solid when mixed with excess concentrated sulphuric (VI)
      acid (1mk)
3. A student was asked to prepare dry lead (II) sulphate salt using the following reagents; dilute nitric (V) acid, lead (II) carbonate and magnesiumsulphate solution. Describe how the salt can be prepared.(3 mks)
4. In a reaction 20cm³ of 0.1M sodium carbonate completely reacted with 12.5cm³ of dilute sulphuric (VI) acid. Find the concentration of suphuric (VI) acid in moles per litres. (3mks)
5. Whencalcium carbonate is placed in a solution of hydrogen chloride gas in water, there is effervescence while there is no effervescence when placed ina solution of hydrogen chloride gas dissolved in methylbenzene .Explain this observation (2mk)
6. Study the chart below for the Contact process and other extensions.
   
   
   1. Identify the substances: (2 mks)
      Q ……………………………………………………………………………………………………
      P …………………………………………………………………………………………..………….
      R……………………………………………………………………..…………………………………
      N……………………………………………………………………………………………………….
   2. Name solution M and state its colour. (1 mk) 
7. Use the reaction scheme below to answer the questions that follow.
   
   
   1. Give one necessary condition for process P
   2. Name the Process P. (1/2 mark)
   3. Draw and name the structure of compound M (11/2 mark)
8. Use the bond energies given below to answer the questions that follow.
   Bond Bong energy (KJ /mole)
   C – H 414
   Cl – Cl 244
   C – Cl 326
   H – Cl 431
   
   1. Calculate the heat change for the reaction. (3mks)
      CH_4(g) + Cl_2(g) CH₃Cl_(g) + HCl_(g)
   2. State the condition necessary for the above reaction to occur. (1 mk)
9. Using dots (.) and crosses (x) to represent electrons, show:
   1. bonding in sodium chloride (1 mk)
   2. the structure of an ion illustrated by the formula  (1 mk)
10. On complete combustion of a hydrocarbon; 1.257g of carbon (IV) oxide and 0.514g of water were produced. If the relative molecular mass of the hydrocarbon is 84, determine the molecular formula of the hydrocarbon (C=12,H=1,O=16) (4mks)
11. Below is a diagram of set-up of apparatus that is used to investigate the effect of electric current on a binary electrolyte, lead (II) bromide.
    
    1. Explain what is meant by a ‘binary electrolyte’. (1mark)
       
    2. State the importance of heating in the above experiment. (1mark)
    3. Give an observation made at the cathode (1 mark)
12.    
    1.    
       1. Name the following organic compounds. (2marks)
          
          1. CH₃ – CH=C – CH₂– CH₂–CH₃
                                I
                              CH₃
          2. CH₃ CH₂CH₂CH₂CH₃
       2. Describe one chemical test that can be used to distinguish between substances (a) and (b) above. (1 mark)
13.    
    1. Define the term solubility. (1mk)
    2. 35g of salt W were added to 60cm³ of water at 25ºC.After stirring 5g of crystals of salt W were filtered out. Determine the solubility of salt W at 25ºC. (2mks)
14. Temporary water hardness can be removed by boiling
    
    1. What is hard water? (1 mk)
    2. Name the anion responsible for temporary hardness of water. (1 mk)
    3. State one advantage of hard water. (1mk)
15.    
    1. State Graham’s law. (1mark)
    2. 60cm³ of oxygen gas diffused through a porous hole in 50 seconds. How long will it take 80cm³ of sulphur (IV) oxide, SO₂ to diffuse through the same hole under the same conditions. (S = 32, O=16). (2marks)
16. The set-up below shows laboratory preparation of hydrogen gas, use it to answer the questions that follow.
    
    
    1. Identify two mistakes in the set-up (2 mks)
    2. Why is itnot advisable to use potassium metal as an alternative of zinc for the preparation of hydrogen gas? (1mks)
17. The apparatus below was set up to show the catalytic oxidation of ammonia. Study the diagram and answer the questions that follow
    
    
    1. Write an equation for the reaction that takes place in the gas jar
    2. What is the role of hot platinum wire?
    3. Write the formula of the complex ion formed when excess ammonia gas is passed through a solution containing Zn2+ ions. (1mk)
18. The diagram below shows the set-up that was used to prepare and collect sulphur (iv) oxide gas.
    
    
    1. Identify solid P (1mk)
    2.      
       1. Why is it possible to collect sulphur (IV) Oxide as shown? (1mk)
       2. What happened to the red flower? (1mk)
19. Hydrogen sulphide gas was passed through a solution of iron(III) chloride
    
    1. State and explain the observations made (2mks)
    2. Write an ionic equation for the reaction taking place in (i) above (1mk)
20. A Certain mass of a metal reacted with excess dilute hydrochloric acid at 25ºC. The volume was recorded after every 30secs. The results were presented as shown below.
    
    
    1. Name one piece of apparatus that may be used to measure the volume of the gas liberated. (1mk)
    2.    
       1. On the same axis, sketch the curve that would be obtained if the experiment was repeated at 35ºC (1mk)
       2. Explain how increase in temperatureaffects the rate of a chemical reaction. (2mks)
21. The set up below was used to prepare dry hydrogen chloride gas.
    
    
    1. Complete the diagram to show how dry hydrogen chloride gas is collected. (2marks)
    2. Identify liquid Q (1mark)
    3. Write a balanced equation for the reaction that produces hydrogen chloride gas in the above experiment (1mark)
22. The relative atomic mass of an elementR is 10.28; it has two isotopes 10 R and 11R.Calculate the relative percentage abundance of each isotope. (3marks)
23. Below is a sketch of a reaction profile.
    
    
    1. On the diagram show the heat of reaction ∆H (1mk)
    2. State and explain the type of reaction represented by the profile (2mks)
24. Describe how you would obtain oil from groundnuts. (2mks)
25. State any two differences between luminous and non-luminous flames (2mks)
26. A sample of water is suspected to contain some dissolvedchloride ions. Describe a chemical test for establishing the presence of the chloride ions in the water sample. (2mks)
27. Sketch a graph of temperature against time for a pure substance A with a melting point of 10ºC and boiling point of 80ºC and it is heated from 0ºC to 90ºC. (3marks)

MARKING SCHEME

1. The apparatus shown below was used to investigate the effect of carbon(II) oxide on copper(II)oxide.
   1. State the observation that was made in the combustion tube by the end of the experiment. (1 mark)
      Brown solid is formed
   2. Write an equation for the reaction that took place in the combustion tube. (1mark)
      CuO_(s) + CO_(g) → CO_2(g) + Cu_(s)
   3. Why is it necessary to burn gas coming out of tubeK? (1mark)
      The gas is poisonous/toxic
2. Name the process which takes place when:
   
   1. Iodine changes directly from solid to gas (1mk)
      Sublimation
   2. The process of hardening rubber by heating it together with sulphur(1mk)
      Vulcanisation
   3. White sugar changes to black solid when mixed with excess concentrated sulphuric (VI) acid (1mk)
      Dehydration
3. A student was asked to prepare dry lead (II) sulphate salt using the following reagents; dilute nitric (V) acid, lead (II) carbonate and magnesiumsulphate solution. Describe how the salt can be prepared.(3 mks)
   Add excess lead (II) carbonate to the dilute nitric(IV) acid. Filter the mixture to get  Pb(SO₃). React the filtrate with magnesium sulphate solution. Filter the mixture to obtain lead(II) sulphate as the residue. Rinse the residue with distilled water and dry between filter papers
4. In a reaction 20cm³ of 0.1M sodium carbonate completely reacted with 12.5cm³ of dilute sulphuric (VI) acid. Find the concentration of suphuric (VI) acid in moles per litres. (3mks)
   Moles of Na₂CO₃ used:
   If 1000cm³ → 0.1moles 
   therefore 20cm³ →²⁰/₁₀₀ x 0.1 = 0.002 moles 
   Equation: 
   Na₂CO_3 aq+ H₂SO_4aq → Na₂SO_4 aq + H₂O_(I) + CO_2(g) 
   Mole ratio of Na₂CO₃ : H₂SO₄ is 1:1:
   Moles of H₂SO₄ acid used: 
   If 1 mole of Na₂CO₃ = 1 mole of H₂SO₄ 
   therefore 0.002 moles of Na₂CO₃ = ^0.002/₁ x 1 = 0.002moles
   Molarity of H₂SO₄ :
   If 12.5cm³ = 0.002 moles
   therefore 1000cm³ = ¹⁰⁰⁰/_12.5 x 0.002
   = 0.16M
5. When calcium carbonate is placed in a solution of hydrogen chloride gas in water, there is effervescence while there is no effervescence when placed ina solution of hydrogen chloride gas dissolved in methylbenzene .Explain this observation (2mk)
   Water is a polar solvent which enables hydrogen chloride gas to dissolve and ionise into free hydrogen and chloride ions. The hydrogen ions are responsible for the acidity of the solution while methylbenzene is a non-polar solvent therefore HCl does not ionise in it after dissolving
6. Study the chart below for the Contact process and other extensions.
   1. Identify the substances: (2 mks)
      Q - Air/Oxygen
      P - Conc sulphuric(VI) Acid
      R - Sulphuric (VI) acid
      N - Sulphur (IV) oxide
   2. Name solution M and state its colour. (1 mk) 
      Name - Copper(II) sulphate
      Colour - Blue
7. Use the reaction scheme below to answer the questions that follow.
   
   1. Give one necessary condition for process P
      Heat of beteween 160ºC and 180ºC , Reject a range of temperatures
   2. Name the Process P. (1/2 mark)
      Dehydration
   3. Draw and name the structure of compound M (11/2 mark)
      
8. Use the bond energies given below to answer the questions that follow.
   Bond Bong energy (KJ /mole)
   C – H 414
   Cl – Cl 244
   C – Cl 326
   H – Cl 431
   
   1. Calculate the heat change for the reaction. (3mks)
      CH_4(g) + Cl_2(g) CH₃Cl_(g) + HCl_(g) 
      Bonds broken: 
      Four H-C bonds = +1656
      One CL-Cl bond = 1 x 244 = +244
      Total heat absorbed = + 1900
      Bonds formed: 
      Three H-C bonds = 3 x 414 = -1242
      One C-CL bond = 1 x 325 = -326
      One H-Cl bond = 1 x 431 = -431
      Total bonds released = -1999
      ΔH = +1900 +(-1990)
      = -99kJmol
   2. State the condition necessary for the above reaction to occur. (1 mk)
      Sunlight or U.V light
9. Using dots (.) and crosses (x) to represent electrons, show:
   1. bonding in sodium chloride (1 mk)
      
   2. the structure of an ion illustrated by the formula Al3+ (1 mk)
      
10. On complete combustion of a hydrocarbon; 1.257g of carbon (IV) oxide and 0.514g of water were produced. If the relative molecular mass of the hydrocarbon is 84, determine the molecular formula of the hydrocarbon (C=12,H=1,O=16) (4mks)
    Mass of carbon in the Co₂ :
           12        x 1.257 = 0.3428g 
    12+(2 x 16)
    Mass of H in H₂O
           12        x 0.514 = 0.0571g 
    1 x 2(+16)
    

    Element	C	H
    Mass	0.3428	0.0571
    Moles	0.3428 = 0.0286    12	0.0571 = 0.0571     1
    Mole Ratio	0.0286 = 1 0.0286	0.0571 = 1.99≈ 2 0.0286

    Empirical formula is
    CH₂ 
    (CH₂)n = 84
    {12 + (1 x 2)}n = 84
    14n = 84
    n = 6
    Molecular formular is (CH₂)₆ = C₆H₁₂
11. Below is a diagram of set-up of apparatus that is used to investigate the effect of electric current on a binary electrolyte, lead (II) bromide.
    
    1. Explain what is meant by a ‘binary electrolyte’. (1mark)
       An electrolyte which has only one type of anion and cation
    2. State the importance of heating in the above experiment. (1mark)
       To melt the solid lead(II) bromide so that the ions become free and mobile
    3. Give an observation made at the cathode (1 mark)
       Grey beads are formed
12.    
    1.    
       1. Name the following organic compounds. (2marks)
          
          1. CH₃ – CH=C – CH₂– CH₂–CH₃
                                I
                              CH₃ 
             3 methyl hex-2-ene
          2. CH₃ CH₂CH₂CH₂CH₃ 
             Pentane
       2. Describe one chemical test that can be used to distinguish between substances (a) and (b) above. (1 mark)
          Add sew drops of orange/yellow bromine water to each separately: Brown bromine water will be decolorised by a substance (a) while in substance(b), the brown colour remains brown. 
          Note: acidified KM_nO₄ or acidifies K₂Cr₂O₇ can be used in place of bromine water
13.    
    1. Define the term solubility. (1mk)
       The maximum mass of the solute required to saturate 100g of the solvent at a particular
    2. 35g of salt W were added to 60cm³ of water at 25ºC.After stirring 5g of crystals of salt W were filtered out. Determine the solubility of salt W at 25ºC. (2mks)
       Mass of salt dissolved = (35 - 5)g = 30g
       If 60cm³ of water = 30g of salt therefore 100cm³ of water = ¹⁰⁰/₆₀ x 30 = 50g
       Thus solubility = 50g/100g of water
14. Temporary water hardness can be removed by boiling
    
    1. What is hard water? (1 mk)
       Water that does not readily lather with soap
    2. Name the anion responsible for temporary hardness of water. (1 mk)
       Hydrogen Carbonate
    3. State one advantage of hard water. (1mk)
       Provides calcium which is essential for strengthening bonds
       Used in brewing
       Forms a layer of carbonate as lining in lead water pipes preventing lead poisoning
15.    
    1. State Graham’s law. (1mark)
       The rate of diffusion of a gas at a cpnstant temperature and pressure is inversely proportional to the square root of its density
    2. 60cm³ of oxygen gas diffused through a porous hole in 50 seconds. How long will it take 80cm³ of sulphur (IV) oxide, SO₂ to diffuse through the same hole under the same conditions. (S = 32, O=16). (2marks)
       Time taken by 80cm³ of O₂
       If 60cm³ of O₂ = 50 sec
       80 cm³ = ⁸⁰/₆₀ x 50 = 66.67 secs
       TO₂  =  √MMO₂ 
       TSO₂  √MMSO₂
       66.67 =   √(16 x 2)  
       TSO₂    √32+(16x2)
       66.67 = √32 
       TSO₂     √64
       TSO₂ x √32 = 66.67 x √64
       TSO₂ = 94.29sec
16. The set-up below shows laboratory preparation of hydrogen gas, use it to answer the questions that follow.
    1. Identify two mistakes in the set-up (2 mks)
       The funnel has not been dipped into the reacting mixture
       Wrong method of collecting hydrogen gas
    2. Why is itnot advisable to use potassium metal as an alternative of zinc for the preparation of hydrogen gas? (1mks)
       Potassium reacts explosively with dilute acids
17. The apparatus below was set up to show the catalytic oxidation of ammonia. Study the diagram and answer the questions that follow
    1. Write an equation for the reaction that takes place in the gas jar
       4NH_3(g) + 5O_2(g) → 4NO_(g) + 6H₂O
    2. What is the role of hot platinum wire?
       Catalyses the reaction/is a catalyst
    3. Write the formula of the complex ion formed when excess ammonia gas is passed through a solution containing Zn2+ ions. (1mk)
       
18. The diagram below shows the set-up that was used to prepare and collect sulphur (iv) oxide gas.
    1. Identify solid P (1mk)
       Sodium sulphite or potassium sulphite
    2.      
       1. Why is it possible to collect sulphur (IV) Oxide as shown? (1mk)
          SO₂ is denser  than air
       2. What happened to the red flower? (1mk)
          Turned white/got bleached
19. Hydrogen sulphide gas was passed through a solution of iron(III) chloride
    
    1. State and explain the observations made (2mks)
       Yellow/brown solution of iron(II) chloride turns to pale green due to reduction to iron(II) chloride by H₂S
       Yellow precipitate is formed due to oxidization of H₂S to sulphur
    2. Write an ionic equation for the reaction taking place in (i) above (1mk)
       H₂S_(g) + 2Fe³⁺_(aq) → 2Fe³⁺_(aq) + S_(s) + 2H⁺_(aq)
20. A Certain mass of a metal reacted with excess dilute hydrochloric acid at 25ºC. The volume was recorded after every 30secs. The results were presented as shown below.
    
    1. Name one piece of apparatus that may be used to measure the volume of the gas liberated. (1mk)
       Graduated syringe/graduated cylinder
    2.    
       1. On the same axis, sketch the curve that would be obtained if the experiment was repeated at 35ºC (1mk)
          
       2. Explain how increase in temperatureaffects the rate of a chemical reaction. (2mks)
          An increase in temperature results in an increase in the kinetic energy of the reacting particles. This makes the particles to move faster and collide more frequently with sufficient energy to cause more successful collissions per unit time. Thus increasing the rate of reaction.
21. The set up below was used to prepare dry hydrogen chloride gas.
    
    
    1. Complete the diagram to show how dry hydrogen chloride gas is collected. (2marks)
    2. Identify liquid Q (1mark)
       Conc Sulphuric(IV) acid
    3. Write a balanced equation for the reaction that produces hydrogen chloride gas in the above experiment (1mark)
       NaCl_(s) + H₂AO_(I) → NaHSO₄ + HCl_(g)
22. The relative atomic mass of an elementR is 10.28; it has two isotopes 10 R and 11R.Calculate the relative percentage abundance of each isotope. (3marks)
    Let the abundance of 10_R be x%
    Hence abundance of "R" will be (100 - x)%
    10.28=(x × 10) +11(100 - x)1
                  100              100 
    10.28=10x  +1100 - 11x
               100        100 
    10.28 = 10x + 1100 - 11x
    1028 - 1100 = 10x - 11x
    -72 = -x
    ^-72/_-1 = ^x/_-1 
    Thus 10_R = 72%
    "R = (100 -72) = 28%
23. Below is a sketch of a reaction profile.
    
    1. On the diagram show the heat of reaction ∆H (1mk)
       
    2. State and explain the type of reaction represented by the profile (2mks)
       Endothermic reaction becasue products have more heat energy than the reactants 
24. Describe how you would obtain oil from groundnuts. (2mks)
    Place the ground nuts in a motor and crush using a pestel. Add propanone or ethanol little by little as crushing continues. Decant the mixture into an evaporating dish. Place the evaporating dish and its contents in the sun for propanone /solvent to evaporate and leave behind the oil
25. State any two differences between luminous and non-luminous flames (2mks)
    

    Luminous Flame	Non-luminous flame
    Long and wavy Produces much light Produces less heat Produces soot Burns quietly Has four zones	Short and steady Produces less light Produces more heat Not sooty Burns noisily Has three zones

26. A sample of water is suspected to contain some dissolvedchloride ions. Describe a chemical test for establishing the presence of the chloride ions in the water sample. (2mks)
    To the sample of water in a test-tube add about 3 drops of lead(II) nitrate solution. If a white precipitate is formed which is soluble on warming, then chloride ions are present, confirmed.
27. Sketch a graph of temperature against time for a pure substance A with a melting point of 10ºC and boiling point of 80ºC and it is heated from 0ºC to 90ºC. (3marks)