Chemistry Paper 1 Questions and Answers - Kigumo Mocks 2021 Exams

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QUESTIONS

Answer all the questions

  1.                  
    1. What name is given to a compound that contains Carbon and Hydrogen only (1mk)
    2. Octane is a compound containing Carbon and Hydrogen
      1. What method is used to obtained Octane from Crude Oil (1mk)
    3. State one use of Butane (1mk)
  2. Starting with Potassium Chloride, describe how a pure sample of Lead(II) Chloride can be prepared in the laboratory. (3mks)
  3. When Magnesium burns in air, it forms a few solid and a grey-green solid. When a few drops of water are added to the mixture a gas that turns red litmus paper blue is evolved. Identify the:
    1. White solid (1mk)
    2. Gas evolved and state its use
      Name of the gas ………………………. (1mk)
      Uses of the gas ………………………… (1mk)
  4. Iron is extracted from its ore by the blast furnace process.
    1. Name one ore from which iron is extracted. (1mk)
    2. One of the impurities in iron is removed in the form of calcium silicate. Write an equation the reaction in which calcium silicate is produced. (1mk)
    3. Give one use of iron (1mk)
  5. During the electrolysis of Aqueous Lead (II) Chloride using Lead electrolysis, a current of 0.5 amperes was passed through the cell for 5 hours.
    1. Write an ionic equation for the reaction that took place at the anode. (1mk)
    2. Determine the change in mass of the anode which occurred as a result of the electrolysis process (Pb = 207, 1 Faraday = 96,500 Coulombs.) (2mk)
  6.                      
    1. Distinguish between nuclear fission and nuclear fussion. (2mk)
    2. Radio-active emits three different particles. Give the symbol of the particle with the highest mass (1mk)
  7. An element Q has two Isotopes Q – 36 and Q – 40 which occur in the ratio Y:4. Given that Relative Atomic Mass of Q is 37.25. Find the value of Y. (3mks)
  8. The grid below represents part of the periodic table. Study the information and answer the questions that follow. The letters do not represent the actual symbol of the elements.
    8 dfuaygfduyad
    1. How does the atomic radius of T compare with that of Y. (1mk)
    2. Write an equation for the reaction that would occur between E and Z. (1mk)
    3. Which element would form a trivalent cation? (1mk)
  9.              
    1. State Graham’s law of diffusion (1mk)
    2. A volume of 120cm3 of Nitrogen gas diffused through a Membrane in 40seconds, how long will 240cm3 of Carbon (iv) Oxide diffuse through the same Membrane. (N = 14, C = 12, O = 16) (2mks)
  10. Use the information below on solubility to answer questions that follow

    Salt

    Solubility in g/100g of H2O

    80ºC

    20ºC

    Na2Co3

    80

    31

    KClO3

    55

    12

    A mixture containing 30g of Potassium Chlorate and 30g of Sodium Carbonate in 100g of water at 80ºC was cooled to 20ºC. Some Crystals are formed.
    1. Which of the two salts crystallized out and by how much? (2mks)
    2. Name the method used to obtain crystals in the above salts. (1mk)
    3. Name the salt that will be unsaturated at 20ºC (1mk)
  11. Study the flow chart below and answer the questions that follows.
    11 zaiuuhdiuahda
    Identify
    1. Solid J (1mk)
    2. Solution Q (1mk)
  12.                                
    1. Half-life of a radio-active element is 30 days. Define the term half-life. (1mk)
    2. Calculate the time required for its mass to reduce to 37.5 %(2mks)
  13. A compound was analysed and found to contain 24.27% Carbon, 4.08% Hydrogen and the rest is Oxygen. If the molar mass of the compound is 99. Determine the molecular formula of the compound. (C = 12, H = 1, O = 16) (3mks)
  14. The diagram was used to prepare and collect Sulphur (iv) Oxide gas
    14 aygduyad
    1. Identify Solid H (1mk)
    2. State two properties of SO2 that makes possible to be collected in method shown. (1mk)
    3. What are the Optimum conditions of conversion of SO2 to SO3 (1mk)
  15. The table below shows pH values of solutions A, B, C and D.

    Solution

    A

    B

    C

    D

    pH Value

    14

    2

    11

    7

    1. Which solution is likely to be sugar solution (1mk)
    2. A few drops of Methyl-Orange indicator were added to solution A. State and explain the observations made. (2mks)
  16.                        
    1. Explain why the metals Magnesium and Aluminium are good conductors of electricity. (1mk)
    2. Other than cost, give two reasons why aluminium is used for making electric cables while Magnesium does not. (2mks)
  17. The below graph shows a heating curve for substance W. Study and answer the questions that follow
    17 auygduyagda
    1. What is the melting point of substance W.? (1mk)
    2. In terms of kinetic theory of matter, explain what happened to the particles in region CD (2mks)
  18.                      
    1. Name the catalyst used for the catalytic oxidation of ammonia during Ostwald process. (1mk)
    2. State and explain the observations made when aqueous ammonia is added to copper (ii) sulphate solution drop wise till in excess. Use equations if necessary. (2mks)
  19. In an experiment, Carbon(iv) Oxide gas was passed over heated coke and the gas produced collected as shown in the diagram below;
    19 adguyagda
    1. Write an equation for the reaction that took place in the combustion tube. (2mk)
    2. Name another substance that can be used instead of potassium hydroxide. (1Mk)
  20. Hydrogen can be prepared by reacting Zinc with dilute hydrochloric acid.
    1. Write an equation for the reaction. (1mk)
    2. Name an appropriate dry agent for hydrogen gas. (1mk)
    3. Explain why copper metal cannot be used to prepare hydrogen gas. (2mks)
  21. 25.0 cm3 of a solution of Potassium Carbonate neutralized 26.8cm3 of 0.1M hydrochloric acid. Calculate the Molarity of the carbonate. (3mks)
  22. At 200 C and 760mmHg pressure, NO2 and N2O exists in equilibrium as shown in the equation below.
    2NO2(g) â‡Œ  N204(g)        ∆H= -Ve
    Brown     pale yellow
    State and explain the observations that would be made when;
    1. A syringe containing the gaseous mixture is immersed in ice-cold water.(2mks)
    2. The volume of the gaseous mixture in a syringe is reduced. (1mk)
  23. A drop of silver nitrate solution on a glass rod was brought to the mouth of a gas jar containing hydrogen chloride as shown below;
    23 aiuyghduyahd
    1. State and explain the observations made. (2mks)
    2. Write an ionic equation to represent the reaction above. (1mk)
  24.                
    1. Give the systematic name of the following compound, (1mk)
      1. CH3COOCH2CH2CH3
    2. Alkanoic acid can be prepared through oxidation of alcohols by strong oxidizing agent. Name two oxidizing agents.
      1. ………………………… (1/2mk)
      2. ………………………… (1/2mk)
    3. The structure below represents a pleasant-smelling compound;
      CH3-CH2-CH2-COO-CH2CH3
      Give the names of the two organic compounds that can be used in its preparation;
      1. ………………………… (1/2mk)
      2. ………………………… (1/2mk)
  25. Two measuring cylinders were each filled with oxygen and placed in position shown below. After 5 minutes, a glowing splint was then introduced into the mouth of each measuring cylinders. State and explain what was observed in each gas jar (3mks)
    25 aihduiad
  26. Use bond energy value given below to answer questions that follow;

    Bonds

    Bond energy KJM/mol

    H-H

    432

    C=C

    610

    C-C

    346

    C-H

    413

    1. Determine the enthalpy change for conversion of butene to butane by hydrogenation. (2mks)
    2. Sketch an energy level diagram for above enthalpy change. (1mk)
  27. Study the information in the table below and answer the question that follow. (The letters do not represent the actual symbols of the elements).

    Element

    Electron configuration

    Ionization energy KJ/mol

    X

    2,8,8,1

    418

    Y

    2,8,1

    494

    Z

    2,1

    519

    1. Give the general name to which the elements belong. Explain (1mk)
    2. Explain why element Z has the highest ionization energy. (1mk)

MARKING SCHEME

  1.                    
    1. Hydro-Carbon (1mk)
    2. fractional distillation (1mk)
    3. Used as a fuel (1mk
  2. Dissolve KCL in water to form KCL solution. Then react KCL with Pb(NO3)(aq), the salt will react to form PbCL2 and KNO3. Filter to collect PbCL2 as a residue and KNO3 as filtrate. Dry the residue between two filter paper. (3mks)
  3.                        
    1. Magnesium Nitrate (Mg3N2) (1mk)
    2. Ammonia (NH3) (1mk)
  4.                          
    1. magnetite, haematite, (1m)
    2. CaO(s) + SiO2(s) â†’ CaSiO3(s)
    3. Making steel, making alloys.
  5. Anode
    1. 2CL- (aq) + 2e- → CL2(g) (1mk)
    2. Q = IT
      = 0.5 × 5 × 3600
      = 9000 colu (1mk)
      1 mole → 96,500C
      ?         â†’  9,000C
      1 × 9000 = 0.093Mole    (½ mk)
       96,500
      Mass = 0.093 × 207
      = 19.3g (½ mk)
  6.                
    1. Nuclear fussion – Splitting up of heavy nucleid to form small nucleid with absorption of energy. (1mk)
      Nuclear fission – Joining of simple nucleid to form a heavy nucleid with a release of energy. (1mk)
    2. Helium particle 42He (1mk)
  7. R.A.M. = (36 × y) + (40 × 4) (1mk)
                            y + 4
    37.25(y + 4) = 36y + 160
    37.25y = 36y + 160 – 149
    37.25 – 36 =160-149
    1.25y = 11 (1mk)
    Y = 11/1.25
    ≈ 8.8
    ≈ 9 (1mk)
  8.                  
    1. T has a layer atomic radius compared to Y since Y has a greater nucleus pull hence small atomic radius. It has more protons than T. (1mk)
    2. E2+ + Z-1 → E1Z2 or
      Mg(s) + CL2(g) → MgCL2(s)
    3. Element S
  9.              
    1. The rate of diffusion of a gas is inversely proportional to the square root of its density at constant temperature and pressure.
    2.                  
    3. V1 – 120cm3          V2 – 240cm3
      T1 – 40Sec          T2 - ?
      N2 – 28               CO2 – 44
      R1/R2 √(MMR2/MMR1)
      (120/40)/(240/T2)=√(44/28)
      (B/240)/T2= √1.57
      (B/240)/T2 = 1.25
      3 = 1.25 × 240
      T2 = 1.25 × 240
                    3
      T2 = 100.24Sec
  10.                        
    1. KClO3 (1mk)
      30 – 12 = 18g (1mk)
    2. Fraction crystallization (1mk)
    3. Na2CO3 (1mk)
  11.                  
    1. Sulphur (s)
    2. Iron (II) Iodide solution
    3. PbCL2/Lead (II) Chloride        
  12.                  
    1. The time taken for a radio-active substance to disintegrate to half its original mass.
    2. 45 days
  13. Element          C          H        O
    %mass        24.27    4.08   71.65
    R.A.M            12        1         16
    No. of moles 24.27   4.08   71.65
                           12        1        16
                          2.02    4.08    4.4
    Mole ratio      2.02    4.08     4.4
                         2.02     2.02    2.02
                          1           2         2
    E.F.:           C1H2O2      E.F.M. = 46
    M.F. = 99 (M.F.M)
               46 (E.F.M)
    = 2
    M.F. = 2(CH2O2)
    = C2H4O4
  14.                  
    1. Na2SO3 – Sodium Sulphite
    2. Denser than air
    3. Does not react with liquid S
    4.                    
      • Catalyst (V2O5)
      • Temp. 450ºC
      • Pressure 2-3 atm
        Any
  15.                    
    1. Solution D (1mk)
    2. Turns to pink; Solution A is strong base (2mks)
  16.                    
    1. They have mobile electrons (1mk)
    2. Light (1mk)
      Does not react with Weather conditions++
  17.                          
    1. 30ºC
    2. Particles gain energy as temperature rises. The energy absorbed is used to weaken the forces holding the particles together.
  18.                  
    1. Platinium-rhodiun
    2. Pale blue solution form, the deep blue solution
  19.                    
    1. CO2 +C(g)→2CO(g)
    2. Conc. NaOH/ sodium hydroxide.
  20.                    
    1. Zn(s) + 2 HCl(aq) →Zncl2(aq) +H2(g)
    2. Conc. H2SO4/Conc. Sulphuric(vi) acid.
    3. Copper does not react with dilute acids.
  21. 1000→0.1 moles
    26.8→?
    = (0.1×26.8)
          1000
    =0.00268
    Equation K2CO3 +2HCl(aq)→KCl(aq)+CO2(g)+H2O(l)
    2mol. →1mol K2CO3
    Therefore 0.00268→? =(1×0.00268)
                                                  2
    =0.00134moles
    Thus 0.00134 moles →25.0cm3
    ? ←1000cm3
    =(0.00134×1000)
               (25 )
    =0.0536M
  22.                          
    1. Equilibrium shifts to the left ie more of pale yellow decomposed to form brown.
    2. Equilibrium will shift to the right ie more of brown to form pale-yellow ie (N2O4)
  23.                    
    1. A white ppt is formed . This is due to formation of Agcl ie
      AgNO3+HCL(aq) →AgCl(s) + HNO3(aq)
    2. Ag+ (aq) +Cl- (aq) →AgCl(s)
  24.                  
    1.                      
      1. propylethanoate
      2. Acidified KMnO4/Acidified K2Cr2O7
    2.                          
      1. CH3CH2CH2COOH→ butanoic acid
      2. CH3CH2OH → Ethanol
  25. In A the glowing splint relight
    B the splint did not relight
    Because : In B the Oxygen had already excaped due to its density.
  26.                
    26 agduyagyd
  27.                
    1. Alkali metals. They have one electron in their outer energy level.
    2. It has only 2 energy levels thus its electrons are close to the nucleus to remove great amount of energy is required.

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