Chemistry Paper 1 Questions and Answers - Kigumo Mocks 2021 Exams

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.
   
   
   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.
    
    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
    
    
    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
    
    
    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;
    
    
    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) ⇌  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;
    
    
    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)
    
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) → 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
      ?         →  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.                
    
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.