Chemistry Paper 2 Questions and Answers - Achievers Joint Mock Exams 2023

INSTRUCTIONS:

• Answer ALL the questions
• Mathematical tables and silent electronic calculators may be used.
• All working must be clearly shown where necessary.

FOR EXAMINER’S USE ONLY

QUESTIONS

1. The grid below represents the periodic table. Study it and answer the questions that follow. The letters do not represent the actual symbols of elements.
   
   
   1.                    
      1. Which letter represents an element that is least reactive? (1 mark)
      2. Why are elements D and Q referred to alkali earth metals? (1 mark)
   2. How does the atomic radius of W and T compare? Explain. (2 marks)
   3. Select two letters representing elements that would react most explosively. (2 mark)
   4. Write the equation showing how Y forms its ion. (1 mark)
   5. Write the formula of:-
      1. Chloride of D. ( ½ mark)
      2. Nitrate of W. ( ½ mark)
   6. What type of bonding exists between;
      1. G and N. ( ½ mark)
      2. K and Y. ( ½ mark)
   7. Explain why melting point of Y is higher than N. (1 mark)
   8. The 1st, 2nd and 3rd ionization energies (in KJ/mol) of elements G and R are given below.
      

      Element		1st I.E	2nd I.E	3rd I.E
      G		520	7,300	9,500
      R		420	3,100	4,800

      1. Define the term ionization energy. (1 mark)
      2. Apart from the decrease in energy levels, explain the big difference between 1st and 2nd ionization energies. (1 mark)
      3. Calculate the amount of energy in KJ/mol for the process. (1 mark)
         R(g) → R3+(g) + 3e-
2.                
   1. The scheme below shows some organic reactions. Study it carefully and answer the questions that follow.
      
      
      1. Write the formula of compounds. (2 marks)
         1. B
         2. A
      2. Name the type of reaction, reagent and conditions for the reactions of the following steps.
         1. Step 1: (2 marks)
            Type
            Reagent
         2. Step 4: (2 marks)
            Type
            Reagent
         3. Step 5: (2 marks)
            Type
            Reagent
      3. Name reagent C.
      4. Draw and name the structural formula of D. (2 marks)
      5. Name the structure E. (1 mark)
      6. Give one property of compound B. (1 mark)
   2. Polymers and fibres are either synthetic or natural.
      1. Give two examples of synthetic fibres and polymers. (1 mark)
      2. A polymer is formed whose formula is;
         
         Draw the structural formula of the monomers. (2 marks)
3. Study the scheme below and answer the questions that follow.
   
   
   1. Name the impurities removed by the purifier. (2 marks)
   2. What is the work of the heat exchanger? (1 mark)
   3. Write down the chemical equation for the reaction taking place where Nitric (V) acid is formed. (1 mark)
   4. Name;
      1. Compound W. (1 mark)
      2. Substance U. (1 mark)
      3. Gas V. (1 mark)
   5. Write down the formula of compound P. (1 mark)
   6. Other than manufacture of ammonia write down one other use of Nitrogen. (1 mark)
   7. Calculate the mass of Nitrogen in 6.6g of Ammonium Sulphate. (H = 1, S = 32, O = 16). (2 marks)
4. The diagram below represents a paper chromatogram of pure substances W, X, Y and Z.
   
   
   1. Name A. (1 mark)
   2. Explain why substance Y moves faster from origin than X. (1 mark)
   3. Explain the observation made on substance Z in the chromatogram. (1 mark)
   4. The relationship between pressure and volume of a fixed mass of a gas was studied at 25°C. The data was recorded as shown in table below.
      

      Volume (dm3)	0.5	1	2	3
      Pressure (atmosphere)	6	3	1.5	1
      Product of volume and pressure

      1. Complete the table by calculating the products of volume and pressure. (2 marks)
      2. Using the data comment on the relationship between volume and pressure of fixed mass of gas at constant temperature. (1 mark)
   5. Use the information below to answer the questions that follow.
      C(s) + O₂(g) → CO₂(g) ΔH₁ = -393.5 Kj/mol^-1
      H₂(g) + ½ O₂ (g) →  H₂O(g) ΔH₂ = -285.8 Kj/mol^-1
      C₂H₅OH (l) + 3O₂(g) →  2CO₂(g) + 3H₂O(l) ΔH₃ = -1370 Kj/mol^-1
      1. Define the term heat of formation. (1 mark)
      2. Calculate the heat of formation of ethanol. (3 marks)
5.                    
   
   
   1. 1. Sodium is extracted in the Downcell shown below.Name Y. (1 mark)
      2. Down’s cell must operate at high temperature of about 600°C. Explain. (2 marks)
      3. Explain why anode is made of graphite instead of steel though it’s a better conductor. (1 mark)
      4. State the purpose of steel diaphragm. (1 mark)
   2. The set up below was used to prepare and collect dry sample of gas G. During the experiment, cleaned magnesium ribbon was strongly heated before heating the wet glass wool.
      
      
      1. Why was the magnesium ribbon cleaned before it was used? (1 mark)
      2. State the observations that would be noted in the reaction tube. (1 mark)
      3. Name;
         1. Gas G. (1 mark)
         2. Suitable liquid L. (1 mark)
      4. Write equation of reaction in the reaction tube. (1 mark)
6.                    
   1. Study the standard electrode potential below and answer the questions that follow.
      The letters are not the actual symbols of the elements.
      M2+(aq) + 2e- → M(s) E^θ = -0.76V
      N2+(aq) + 2e- → N(s) E^θ = -2.37V
      2P+ + 2e- → 2P(s) E^θ = +0.80V
      R2+ + 2e- → R(s) E^θ = - 0.14V
      1. The standard electrode potential of Fe²⁺ is -0.44 volts. Select the element which would be best to protect iron from rusting. (1 mark)
      2.            
         1. Calculate the Eθ value for cell represented as M(s) / M²⁺(aq) // P+(aq) + P(s). (2 marks)
         2. Draw the electrochemical cell represented in b(i) above. (2 marks)
   2. The diagram below represents an experiment by a student using electrodes A and B.
      
      
      1. Name the products at the electrodes. (1 mark)
      2. Write equation of reaction at each electrode. (1 mark)
   3. During purification of copper by electrolysis, 1.48g of copper was deposited when a current was passed through aqueous copper (II) sulphate for 2½ hours. Calculate the amount of current that was passed. Cu = 63.5 and 1 Faraday = 96500C. (3 marks)
7.                  
   1. Define the term solubility. (1 mark)
      

      Temp oC	0	8	20	40	60	80
      Solubility in g/100g  of the H2O	254	225	140	80	25	10

   2. Study the table below and answer the questions that follow.
      1. Plot a graph of solubility in g/100g of water of copper (II) sulphate against temperature. (4 marks)
         
      2. From the graph,
         1. How does the solubility of Copper (II) sulphate vary with temperature? (1 mark)
         2. Determine solubility of Copper (II) sulphate in g/100g water at 35°C. (1 mark)
      3. If 30g of Copper (II) sulphate are dissolved in 100g of water at 30cC, is the resulting solution saturated, supersaturated or unsaturated. (1 mark)
      4. A saturated solution of copper (II) sulphate is cooled from 70°C to 20°C.
         1. Should the mass of copper (II) sulphate be reduced or increased for the solution to remain saturated. (1 mark)
         2. Determine the mass in (iv) (a) above. (2 marks)

MARKING SCHEME

1.              
   1.                
      1. F
      2. Abudant in earth crust ½ and reacts with water to form alkalines solutions
   2. W is bigger than T1 OR T is shorter than W. This is because of increased nuclear charge across the period
   3. R ¹ and N¹ or N¹ and R¹
   4. Y + e → Y-1
   5.                
      1. DCl₂
      2.  W (NO₃)₃
   6.                
      1. Ionic ½ / electrovalent
      2. Covalent
   7. Y is liquid while N½ is a gas. N is a molecular compound with van der waals forces while Y is a liquid with strong covalent bonds
   8.              
      1. Energy required to remove an electron from an atom in gaseous form
      2. The 2nd electron is being removed from a stable energy level
      3. 420 + 3,100 + 4,800 = 8,320
2.                    
   1.            
      1.                
         1. B – CH₃COO CH₂ CH₂ CH₃
            A – CH₃ CH₂ CH₂ Na 
      2.            
         1. Type – oxidation 
            Reagent – Acidified KMno₄ / K₂ Cr₂ O₇¹
         2. Type – Dehydration
            Reagent – Conc H₂SO₄¹
         3. Type – Hydrogenation 
            Reagent – presence of Nickel catalyst
      3. NaoH
      4.        
      5. 2 dibromopropane
      6. Has a sweet smell
   2.          
      1. Polythene
      2. Polychloro ethane
3.            
   1.                
      1. carbon IV oxide
      2. Dust particles
      3. Water vapour etc
         any one
   2. Heat reactants OR Cool reactants
   3. 4NO₂(g) + 2H₂O(l) + O₂(g) → 4HNO₃(aq)
   4. W – Ammonia gas
      U – Water
      V – Nitrogen gas
   5. NH₄NO₃¹
   6. Used in light bulbs1 OR Used in storage of semen
   7. Mass of (NH₄)₂SO₄ = 28 + 8 + 32 + 64 = 132
      if 28g    132g
         ?         6.6
      = (6.6 ×28)/132
      =1.4g 
4.              
   1. Solvent front
   2. Y is more soluble than X 1 or Y has a lower absorption power
   3. Z is insoluble in the solvent
   4.              
      1. Volume
         Pressure
         Product 3.0½ 3.0½ 3.0½ 3.0½
      2. Volume is inversely proportional to pressure 
   5.              
      1. Heat change when 1 mole of a compound is formed from its elements 
      2. 2C + 3H₂ + ½ O₂  → C₂ H₅ OH
         
                   ⇓
         
         2 CO₂ + 3 H₂O
         
         ΔHf + Δ H₃ = 2 ΔH₂ + 3H₂(g)
         ΔHf + Δ H₁ = 3 ΔH₂ – ΔH₃
         = (2 x 393.5) + (3x – 285.8) + 13701
         = -787 + -857.4 + 13701
         = 274.4 KJ Mol^-1
5.            
   1.                          
      1. Chlorine gas
      2. To maintain sodium chloride in molten form to allow ions to be mobile to conduct electricity
      3. Carbon in graphite is resistant to attack by chlorine
      4. To prevent chlorine from mixing with sodium to form sodium chloride
   2.                
      1. To remove magnesium oxide layer on the surface
      2. Bright white flame / light or white powder
      3.                  
         1. Hydrogen gas
         2. concentrated sulphuric
      4. Mg(s) + H₂O(g) → MgO(s) + H₂(g)
6.                    
   1.            
      1. element N ½, it has the lowest reduction potential and would thus get easily oxidized at the expense of iron ½
      2.            
         1. Eθ = E reduction – E oxidation ½
            Eθ = 0.80 – (-0.76)
            Eθ = +1.56 ½
   2.                    
      1. At A = oxygen gas ½
         at B = Hydrogen gas ½
      2. At electrode A
         4OH-(aq) → 2H₂O(l) + O₂ + 2e^-1
         At electrode B
         2H⁺(aq) + 2e^-  →  H₂(g)
   3. CU ²⁺ (aq) + 2e^- →  CU(s)
      Therefore 63.5g of copper requires 193,000C
      1.48g = ?
      = (1.48g ×193,000)/63.51
      = 4498.2677 C
      
      Since Q = It
      Then I = Q/t = 4498.2677/(2 1/2 ×3600)1 = 0.4998075
      = 0.499807 5 Ampheres
7.                
   1. The maximum amount of solute that can dissolve in 100g of water at a given temperature
   2.                  
      1. Axes
         Plots
         Curve
      2. Solubility decreases as temperature increases
      3. Unsaturated
      4.                          
         1. increase
         2. 70°C = 16.0g
            20°C = 140
            ∴ Mass = 140 – 16g
            = 124