Chemistry Paper 1 Questions and Answers - Momaliche Pre Mock Exams 2023

• Answer all the questions.
• Mathematical tables and silent electronic calculators may be used.
• All working must be clearly shown where necessary.
• All answers should be written in English.

1. Metal Q displaces metals T and U from their oxides but does not displaces metal R. Metal T displaces U form its oxide. Arrange the metals according to their reactivity starting with the strongest reducing agent. (1 mark)
2. Chlorine gas can be prepared in the laboratory using the following two methods;
   Solid substance X and concentrated Hydrochloric acid
   Solid substance X, concentrated sulphuric (VI) acid and solid Sodium Chloride.
   1. Name the solid substance X (1 mark)
   2. What is role of concentrated sulphuric acid in the reaction? (1 mark)
   3. State how dry chlorine gas is collected. (1 mark)
3. A white crystalline solid Q when heated to forms a brown gas, colourless gas that relights a glowing wooden splint and a yellow residue which turns white on cooling. Aqueous solution of Q forms  white precipitate which dissolves in excess ammonia solution to form a colourless solution P.
   1. Write the name and chemical formulae of complex ion in solution P. (2 marks)
      
      1. Name;
      2. Chemical formula;
   2. State the observation made when the aqueous solution of P is reacted with few drops of sodium hydroxide. (1 mark)
4.  
   1. Define term Lattice energy (1 mark)
   2. The reaction between hydrogen gas and oxygen releases energy. A student drew the reaction profile for the reaction between hydrogen gas and oxygen gas.
      
      State two errors made when drawing the reaction profile. (2mks)
5. Ammonia gas is one of the substances recycled in the Solvay process.
   1. Other than water name another substance that is recycled in the process. (1 marks)
   2. Write a balanced chemical equation for the reaction that regenerates Ammonia gas in the process.   (1 mark)
   3. State an industrial use of the only waste product in the Solvay process. (1 mark)
6. Lead (II) iodide is a toxic bright yellow solid which was used as a paint pigment known as ‘iodine yellow’. Describe briefly how you would prepare lead (II) iodide in the laboratory starting with lead (II) oxide. (3 marks)
7. 5.0g of zinc carbonate were allowed to react with 25cm³ of 1M hydrochloric acid until there was no further reaction. Calculate the volume of gas that was formed at s.t.p. (Zn = 65.4, O = 16, C = 12, molar gas volume at s.t.p = 22400 cm³) (3 marks)
8. Atoms of element P can be represented as . Element P reacts with sulphur to form a yellow solid. Using dots (•) and crosses (X) represent electrons, draw the structure of the yellow solid. (S=16). (2 marks)
9. The curve shown below shows the variation of time against temperature for the reaction between sodium thiosulphate and hydrochloric acid.
   
   1. Explain the shape of the curve.                                                                            (2 marks)
   2. Other than temperature name one factor that affects the rate of reaction.            (1 mark)
10. Magnesium ribbon was added to a solution of hydrogen chloride in methylbenzene. Another piece of Magnesium ribbon was added to hydrogen chloride in hydrogen chloride in water. State and explain observations made. (2 marks)
11. State two differences between luminous and non luminous flame of the Bunsen burner. (2 marks)
12. A fuel gas contains 50% of hydrogen gas and 44% of carbon (II) oxide by volume. The rest of is incombustible. Calculate the volume of gas that remains at room temperature when the 100 cm³ fuel gas was ignited. (3 marks)
13. Study the diagram below and answer the questions that follow.
    
    1. Name substances; ( 1 mark)
       1. Q………………………………………………………..
       2. R………………………………………………………..
    2. Write the equation for the reaction that leads to the formation of the yellow solid. (1 mark)
    3. Using a chemical test, describe how you would distinguish between hydrogen sulphide and sulphur (IV) oxide. (1 mark)
14. A gas occupies a volume of 400cm³ at 227oC and 760mmHg.What will be the temperature of the gas when the volume and pressure of the gas is 100cm³ and 380mmHg respectively. (2 marks
15. For each of the following experiments, give the observations, and the type of change that occurs (Physical or chemical) (3 marks)
    

    Experiment	Observation	type of change
    A few drops of concentrated sulphuric acid added to small amounts of sugar
    A few crystals of Iodine are heated gently in a test tube
    A few crystals of copper (II) Nitrate are heated strongly in a test tube.

16.  
    1. Define solubility of a solute. (1 mark)
    2. The solubility of potassium nitrate is 120g/100g of water at 80°C and 70g/100g of water at 20°C.What mass of the salt would crystallize if 80g of potassium nitrate solution saturated at 8°C was cooled to 20°C     ( 2Marks)
17. Zinc metal reacted with dilute hydrochloric acid. The gas produced was then passed over heated copper (II) oxide in a combustion tube.
    1. State two precautions that must be considered when the gas reacts with copper (II) Oxide in the combustion tube. (2 marks)
    2. Write a balanced chemical equation between zinc and dilute hydrochloric acid. (1 mark)
18. The table below shows ammeter readings recorded when two equimolar solutions were tested separately.
    

    Electrolyte	Current (A)
    Dilute Sulphuric (VI) Acid	7.210
    Ethanoic Acid	4.011

    1. Explain the difference in the ammeter readings. (2marks)
    2. Compare the reactivity of equal length of magnesium ribbon with each of the electrolytes. (1 mark)
19. Study the scheme below and answer questions that follow
    
    1. Identify reagent A. (1mk)
    2. Name process B (1mk)
    3. What does PVC stand for? (1mk)
20. One of the disadvantages of hard water is wastage of soap.
    1. State one other disadvantage                                                                                                               (1mk)
    2. The table below shows tests carried out in a sample of water and the results obtained.
       

       Sample	Results	Observations
       A	Addition of sodium hydroxide drop wise until excess	White precipitate which dissolves in excess
       B	Addition of excess ammonia solution	White precipitate
       C	Addition of dilute nitric (V) acid followed by barium chloride	White precipitate

       1. Identify the anion present in the water sample (1 Mark)
       2. Write an ionic equation for the reaction in C (1 Mark)
21. A piece of sodium was burnt in excess oxygen gas. The product obtained was shaken with water to make a solution.
    1. Write a balanced equation for reaction between the product formed and water. (1 mark)
    2. State and explain the observation made when red and blue litmus papers are dipped into the solution.  (2 marks)
22. Aluminium chloride and sodium chloride are both chlorides of period 3 elements in the periodic table. Use this information to explain the following observations.
    1. A solution of Al₂Cl₆ in water turns blue litmus paper red while that of sodium Chloride does not.  (1½ marks)
    2. Sodium chloride has a melting point 801°C is while Al₂Cl₆ sublimes 183°C. (1½ marks)
23. The ionization energies of elements A and B are 495.9kJ/mol and 739.9kJ/ mol respectively.
    Both elements are in the same group of the periodic table.
    1. What is ionization energy? (1 mark)
    2. Compare the reactivity of elements A and B . Explain your answer. (2 marks)
24. Study the information given in the table below and answer the questions below.
    

    Bond	Bond energy(kJ/mol)
    C-H  H-CI  C-CI  CI-CI  C-C	413  431  346  244  347

    1. Calculate the enthalpy change for the reaction below.
       C₂H_6(g) + Cl_2(g) → CH₃CH₂Cl_(g) + HCl_(g) (2 marks)
    2. State a condition required for the reaction in (a) above to take place. (1 mark)
25. The diagram below represents a set-up that can be used to obtain nitrogen gas in the laboratory. Use the information on the diagram to answer the questions that follow
    
    1. Describe the chemical test for liquid A. (1 mark)
    2. What observation is made in the combustion tube during the reaction? (1 mark)
    3. State two uses of gas B. (1 mark)
26.  
    1. State Graham’s law of diffusion. (1mk)
    2. 50cm³ of nitrogen (ii) oxide was allowed to diffuse through a porous membrane in 20 seconds. Calculate the time taken by equal volume of carbon (ii) oxide to diffuse through the same membrane. (C=12, N=14, O=16). (2mks)
27. Nitrogen (IV) oxide dissolves and reacts with Sodium hydroxide solution to form two salts and water.
    1. What is the nature of Nitrogen (IV) oxide? {1 mark}
    2. Write the Ionic equation for the reaction that takes place. {1 mark}
28. When powdered brass was reacted with excess dilute sulphuric (VI) acid, a solid residue was left.
    1. Name the residue. (1 mark)
    2. Explain why the residue was left. (1 mark)
    3. State another observation made (1 mark)
29. During manufacture of sulphuric (vi) acid, sulphur (iv) oxide is oxidised to sulphur (vi) oxide in the presence of vanadium oxide catalyst as shown below:
    2SO_2(g) + O_2(g)  2SO_3(g)         ΔH = − 197kJ/mol
    The reaction is carried out at a pressure of 3 atmospheres and a temperature of 4500C. State and explain the effect on the yield of sulphur (vi) oxide if the reaction is:
    1. Carried out at 3 atmospheres and 600°C. (2mks)
    2. In absence of a catalyst. (2mks)

MARKING SCHEME 

1. R - Q - T - U
      → increasing
2.  
   1. Manganese (IV) Oxide KMnO₄ 
   2. It reacts with sodium chloride to produce hydrogen chloride which in turn reacts with Manganese (IV)Oxide to produce chlorine gas.
   3. It is collected by downward delivery since it is denser than air 
3.  
   1.  
      1. Tetra amine Zinc (ll) ions
      2. [Zn(NH₃)₄]²⁺ 
   2. White precipitate is formed.
4.  
   1. Energy change when one mole of an ionic compound is formed from mits constituent ions in gaseous state.
   2.  
      • Products should be at a lower energy than products
      • Labelling of the y-axis ( energy in KJ/mol)
5.  
   1. Carbon (IV) Oxide
   2.  Ca(OH)_2(aq) + 2NH4Cl^(aq) → CaCl_2(s) + 2NH_3(g) + 2H₂O_(l)    
   3.  
      • Used as a drying agent of gases that do not react with it.
      • Used to extract sodium metals.
6.   
   • Add Lead (II) Oxide to Nitric (V) acid until it is in excess
   • Filter to remove unreacted Lead (II) Oxide
   • To filtrate add Sodium Iodide and filter off to remove Lead (II) Iodide as a residue.
   • Wash the residue with distilled water.
   • Dry the residue between the filter paper.
7. ZnCO_3(s) + 2HCl(_aq) → ZnCl_2(aq) + CO_2(g) + H₂O(l)
   1.0 mole = 1000cm³
        ?        = 25cm³ 
   25 × 1 
    1000
   = 0.025moles
   HCl : CO2
     2 :    1
   2 → 0.025
   1 → ?
   1  × 0.025
        2 
   = 0.0125moles
   1.0 moles → 22400
   0.0125moles → ?
   0.0125 × 22400
   = 280cm³ 
8.  
   P - 2.8.1
   S - 2.8.6
   
9.  
   1. Time taken by reaction reduces with increase in temperature. Kinetic energy of reacting particles increases increasing then ftrequency of collision.
   2.  
      • Concentration of reacting substances/ Surface area 
      • Presence of a catalyst
10.  
    • In methylbenzene there was no effervescence but in water there was effervescence.
    • Hydrogen chloride ionises in water. Hydrogen ions react with magnesium producing hydrogen gas.

11. Luminous	Non luminous
    Yellow and sooty	Blue and non sooty
    Fairly hot	Very hot
    Long and wavy	Short and Steady

12. Hydrogen = ⁵⁰/₁₀₀ ×100       2H_2(g) + O_2(g) → 2H₂O_(l)
                    = 50cm³
    Carbon (II) Oxide 44/100 × 100.      2CO_(g) + O_2(g) → 2CO^2(g)
                    = 44cm³
    Remaining gases ( 100 − 44)CO²
               =6cm³ incombustible gas
13.  
    1.  
       • Q - dilute hydrochloric acid.
       • R - Copper (II) Sulphate solution
    2. H₂S_(g) + Cl_2(g) → S_(s) + 2HCl_(g)
    3.  
       • Ignote the two gases - hydrogen sulphide burns while mSulpmhur (IV) Oxide does not burn
       • KMnO₄ - white + yellow - SO²
       • K₂Cr₂O₇ - green + yellow - green
14. 227 + 273 = 500K
    P₁V₁ = P₂V₂
      T₁         T₂
    T₂  = P₂V₂T₁
              P₁V₁
    T₂ = 380 × 100 × 500
                760 × 400
        = 62.5K −210.5°C
15.  

    Experiment	Observation	type of change
    A few drops of concentrated sulphuric acid added to small amounts of sugar	white/brown to black solid	Chemical
    A few crystals of Iodine are heated gently in a test tube	Dark grey to Purple vapour	Physical
    A few crystals of copper (II) Nitrate are heated strongly in a test tube.	Blue crystals to black solid, brown gas	Chemical

16.  
    1. Maximum mass of solute required to saturate 100g of the solvent at a particular temperature
    2.  
       
17.  
    1.  
       • Pass hydrogen through combustion tube before heating Copper (II) Oxide to drive out all air.
       • Ignite the excess hydrogen to prevent it from exploding in air
    2. Zn_(s) + 2HCl_(aq) → ZnCl_2(aq) + H_2(g) 
18.  
    1.  
       • Sulphuric (VI) acid being strong acid inoises fully. Solution contains many mobile ions hence the high current.
       • Ethanoic acid being weak acid, ionises partially. Solution contains few mobile ions.
    2. Reaction with H₂SO₄ is higher than with CH₃COOH. H₂SO₄ has more H₊ than CH₃COOH
19.  
20.   
    1. Stains white clothes/ reduce efficiency in briters due to desposition of fur.
    2.  
       1. SO₄²⁻ 
       2. Ba²⁺ + SO₄²⁻ → BaSO4(s)
21.  
    1. 2Na₂O_2(s) + 2H₂O_(l) → 4NaOH_(aq) + O_2(g) 
    2. Red litmus paper changes blue while blue litmus paper remains blue because the solution contain OH⁻ which are basic in nature.
22.  
    1. Al₂Cl₃ hydrolyses/ ionises in water to produce mhydrogen chloride or (H⁺)(_aq) which is acid while NaCl does not ionise/hydrolyse
    2. Sodium chloride has a giant ionic structure with strong ionic bond which require alot of energy to break while Al₂Cl₆ has a molecular structure.
23.  
    1. The minimum amount of energy required to remove an electron in the outermost energy level of an atom in gaseous state.
    2. A is more reactive than B; A has smaller ionization energy (495.9kJ/mol) than B which is (739.9kJ/mol)
24.  
    1.  
       
    2. U.V light
25.  
    1.  
       • To liquid A, add anhydrous Copper(II)Sulphate, white anhydrous Coper (II) Sulphate turns blue
         OR
       • Add anhydrous Cobalt(II)Chloride to liquid A, it turns from Blue Cobalt(II)Chloride to pink
    2.  
       • Orange Lead(II)Oxide turns to grey.
       • Droplets of colourless liquid are formed on the cooler parts of the combustion tube
    3.  
       • Manufacture of ammonia in Haber process
       • In light bulbs; because it is inert.
       • As a refrigirant i.e in storage of Semen for artificial insermination.
26.   
    1. the ratio of the diffusion rate of two gases is the same as the ratio of the square root of the molar mass of the gases.
27.  
    1. It is acidic
    2. 2NO_2(g) + 2OH⁻(_aq) → NO₃⁻_(aq) + NO₂⁻_(aq) + H₂O_(l) 
28.  
    1. Copper
    2. Brass is a mixture of zinc and copper. Zinc reacts with acid but Copper does not. Zinc being more reactive displacrs Hydrogen in the dilute acid faster.
    3. Effervescence is produced/ bubbles mof colourless gas.
29.  
    1. The yield decreases at 600°C; because the reversed mreaction is favoured; since its the reaction that leads to endothermic reaction. i.e SO3 decompose to SO₂ and O₂ 
    2. The yield remains the same. The rate of both reactions slows down / catalyst has no effect on a reaction at equilibrium