Chemistry Paper 1 Questions and Answers - Bunamfan Cluster Pre Mock Exam 2022

Instructions to candidates

•  Answer ALL the questions in the spaces provided in the question paper
• KNEC Mathematical tables and electronic calculators may be used for calculations
• All working MUST be clearly shown where necessary
• Candidates should answer the questions in English

Questions

1. In the industrial preparation of oxygen, state:
   
   1. How dust particles are removed from air. (1 mark)
   2. Why carbon (IV) oxide is removed before the mixture is cooled to – 250C (1 mark)
2.  A form four student accidentally mixed Sodium Carbonate and Calcium Carbonate. Describe how he would obtain a dry sample of Sodium Carbonate from the mixture. (3 marks)
3. The set up below was used to prepare dry hydrogen gas. Study it and answer the questions that follow.
   
   
   1. Identify a mistake in the set up (1 mark)
   2. Write an equation for the reaction for the reaction that produces hydrogen gas(1 mark)
   3. State the chemical test for hydrogen (1 mark)
4. When air is bubbled through pure water (pH 7), the pH drops to 6.0.Explain (2mks)
5. Explain why iron III chloride is fairly soluble in methylbenzene while Magnesium chloride is insoluble. (2 mks)
6. Describe how a solid sample of Lead(II) Chloride can be prepared using the following Reagents:Dilute Nitric Acid, Dilute Hydrochloric Acid and Lead Carbonate. (3marks)
7. 50cm3 of Carbon (IV) Oxide diffuses through a porous plate in 15 seconds. Calculate the time taken by 75cm3 of Nitrogen (IV) Oxide to diffuse through the same plate under similar conditions. (C = 12, 0 = 16, N = 14) (2marks)
8.      
   1. Carbon (IV) oxide is bubbled through Calcium hydroxide until there is no further change.
      Explain using equations the changes observed. (2 marks)
   2. Explain why diamond is used in cutting of glass and drilling. (1 mark)
9. Study the table for certain properties of substances A, B, C and D.
   

   	Melting point °C	Solubility in water	Electrical conduct
   A	-119°C	Soluble	Solution does not conduct
   B	1020°C	Soluble	Solution conducts
   C	1740°C	Insoluble	Doesn't not conduct
   D	1600°C	Insoluble	Conducts at room temperature

   
   Which of the substances A, B, C and D: (4 mks)
   1. Is a metal ……………………………………………………………………………….
   2. Has a simple molecular structure………………………………………………………
   3. Has a giant ionic structure………………………………………………………………
   4. Has a giant covalent structure…………………………………………………………..
10. A compound G reacts with 2 moles of bromine to form another compound whose structural formula is.
    
    
    1. What is the formula and name of compound G (2 marks)
    2. State the observations made when acidified potassium chromate (VI) is added to compound G (1 mark)
11. Study the set-up below and answer the questions that follow
    
    
    1. Identify gas (1 mark)
    2. Write an equation for the reaction that produces gas x. (1 mark)
    3. What is the effect of the gas x above on the red-litums paper (1 mark)
    4. State and explain two observations made when hydrogen sulphide is bubbled through a solution containing iron (III) chloride. (2mks)
12. Aluminium (III) chloride sublimes. Explain why this is possible. (2mks)
13. The table below shows the solubility of a substance at various temperatures. Study it and answer the questions that follow.
    

    Temperature(°C)	Solubility in g/100g of water
    0	36
    40	30
    80	25
    110	20

    
    
    1. What is the meaning of solubility? (1 mark)
    2. What is the physical state of the substance? (1 mark)
    3. State and explain what would happen if a sample of a saturated solution of thesubstance at 40°C was heated to 110°C. (1mark)
14. Study the chart below and answer the questions that follow.
    
    
    1. Name:
       1. Cations present in mixture X. (1mark)
       2. Anions present in the solution. (1mark)
    2. Write an equation to show how the white precipitate in step III is formed. (1mark)
15. Study the diagram below and answer the questions
    
    
    1. What is the process involved in step L (1mark)
    2. Explain how process N and P can be affected (2marks)
16. The scheme below was used to prepare a cleansing agent. Study it and answer the questions that follow.
    
    
    1. Given to the type of cleansing agent prepared by the method above? (1 mark)
    2. Name one chemical substance added in step II (1 mark)
    3. What is the purpose of adding the chemical substance named in c (ii) above? (1 mark)
17. Nitrates of metals A, B, C were heated and the products of the reactions recorded in the table below.
    

    Nitrate of metal	Products
    A	Metal nitrate and oxygen
    B	Free metal, nitrogen (IV) oxide and oxygen gas
    C	Metal oxide, nitrogen (IV) oxide and opxygen gas

    
    
    1. Name two possible identities of metal A. (1mk)
    2. Name the two possible identity of metal B (1mk)
    3. Calcium nitrate is one of the nitrate which forms the products in C. Using chemical equation show how the products are formed. (1mk)
18. State and explain what happens to the masses of the following substances when they are separately heated in open crucibles ;(3mks)
    1. copper metal
    2. Sulphur powder
19. The table below gives the first ionization energies of the alkali metals.
    

    Element	1st ionization energy KJ mol-1
    A	494
    B	418
    C	519

    
    
    1. Define the term ionization energy. (1mk)
    2. Which of the three metals is the least reactive? Give a reason. (2mks)
20. Study the set-up below and answer questions that follow.
    
    
    1. Name the gas that is produced when concentrated sulphuric (VI) acid reacts with the Sodium chloride (1mark)
    2. Why is it necessary to use a funnel in the beaker? (1mark)
    3. How does the gas affect the PH of the water in the beaker? (1mark)
21. The flow chart/diagram below outlines a method of preparing a fertilizer
    
    
    1. Identify U and W (1 mark)
    2. Give the names of salt F and V (1 mark)
    3. Write a balanced equation for the formation of salt F (1 mark)
22.  
    1. Draw a dot (•) and a cross (x) diagram to show bonding in Cl₂O. (1 mark)
    2. Explain why the compound Cl2O has a very low melting and boiling point. (1 mark)
23. Ethene reacts with oxygen according to the equation.
    C₂H_4(g) + 3O_2(g) → 2 CO_2(g) + 2H₂O_(g)
    15.0 cm³ of ethene were mixed with 50cm3 of oxygen and mixture was sparked to complete the reaction. If all the volumes were measured at a pressure of one atmosphere and 250C. Calculate the volume of resulting gaseous mixture. (3 marks)
24. The graph below shows the behavior of a fixed mass of a gas at constant temperature.
    
    
    1. What is the relationship between the volume and the pressure of the gas? (1 mark)
    2. 3 litres of oxygen gas at 1atm atmosphere pressure were compressed to 2atm at constant temperature. Calculate the volume occupied by the oxygen gas. (2marks)
25. Temporary water hardness can be removed by boiling
    1. What is hard water.(1 mark)
    2. Write a chemical equation to show how temporary hardness is removed by boiling. (1 mark)
    3. State one advantage of hard water. (1 mark)
26. A student set-up the experiment below to collect gas K. The glass wool was heated before heating the zinc powder.
    
    
    1. Why was it necessary to heat the moist glass wool before heating the zinc powder?(1 mark)
    2. What observation was made in the boiling tube. (1 mark)
27. During the extraction of lead from its ores one of the main ore used is Galena
    
    
    1. Write an equation for the reaction in roasting furnace. (1 mark)
    2. Name gas P (1 mark)
    3. State one use of lead metal. (1 mark)
28. The empirical formula of a compound is CH2 and it has a molecular mass of 42.
    1. What is the molecular formula of this compound? (1 mark)
    2. Write the general formula of the homologous series to which the compound belongs.(1mk)
    3. Draw the structural formula of the third member of this series and give its IUPAC name. (1mark)

Marking Scheme

1.        
   1. By passing through filters/electrostatic precipitators✓
   2. Carbon (IV) oxide would otherwise solidify and block the pipes✓
2. Add✔ ½ water to the mixture stir ✔ ½ the mixture for all Sodium Carbonate to dissolve.
   Filter ✔ ½ the mixture to obtain calcium carbonate as residue and sodium carbonate as filtrate.
   Heat ✔ ½ the filtrate to evaporate ✔ ½ excess water and leave it to cool slowly for sodium carbonate to crystallize ✔ ½ . Finally filter the product and obtain pure crystals of sodium carbonate.
3.          
   1. Method of gas collection is wrong,gas is lighter than air
   2. Zn_(s) + 2HCl_(aq) → ZnCl_2(aq) +H_2(g)
   3. It burns with a pop sound when ignited
4. Air contains carbon (IV)oxide ;1mk this gas reacts with water to form carbonic acid hence pH drops to 6.0;1mk
5. Iron III chloride is molecular and methylbenzene is also molecular while magnesium II chloride is an ionic compound
6. Dissolve (✓ ½) Lead carbonate in dilute Nitric acid (✓ ½ ) React the mixture with dilute
    Hydrochloric acid (1) Filter (✓ ½ ); to get Lead (II) Chloride (✓ ½ )
7. 75cm³ of CO₂ takes = ^{75 x 15}/₅₀  second ✔ ½ = 22.5 seconds✔½
   Rmm of CO₂ = 12 + 2 x 16 = 44 ✔ ½
   Rmm of NO₂ = 14 + 2 x 16 = 46 ✔ ½
   ^TNO₂/_TCO₂= √^MNO₂/_MCO₂
   TNO2 = 22.5√⁴⁶/₄₄ seconds ✔ ½
   = 23.006s ✔ ½
8.         
   1. Ca(OH)_{2 (aq)} + CO_2(s) → CaCO_3(s) + H₂O_(l)✔ ½
      Lime water forms white ✔ ½ ppt due to the formation of calcium carbonate but in excess calcium carbonate forms colourless solution due to the formation of soluble ✔ ½ calcium hydrogen carbonate.
      CaCO_3(s) + H₂O_(l) + CO_2(g) → Ca(HCO₃)_2(aq) (2 mks)
   2. In diamond each carbon atom is bonded to four other carbon atoms ✔ ½ arranged in a regular tetrahedron shape the whole structure of diamond extends all directions forming a rigid ✔ ½ mass of atoms. (1 mk)
9.           
   1. D
   2. A
   3. B
   4. C
10.    
    1.            
          
    2. acidified potassium chromate (VI) changes from orange to green✔ 1
11.  
    1. Sulphur(iv)oxide✔ 1
    2. Na₂SO_3(s) +2HCl_(aq) → SO_2(g) + 2NaCl_(aq) + H₂O_(l) ✔ 1
    3. the red litmus paper is bleached✔ 1
    4. brown iron( III) ions changes to green due to reduction of iron (III) ions to iron (II) by hydrogen sulphide
12. Two aluminium chloride molecules join to form a diametric molecule;1mk.the diametric molecules are held together by weak van der waals forces which easily break when heated;1mk hence the solid sublimes
13.      
    1. It is the maximum mass of solute that dissolves in 100g of water to form a saturated solution at aparticular temperature.
    2. it is agas
    3. the solution becomes more saturated with the gas
14.  
    1.        
       1. Cu²⁺ , Al³⁺
       2. SO₄^2-
    2. Al³⁺_(aq) + 3OH^-  → Al(OH)_3(s)
15.   
    1.  fractional distillation
    2. N-add water
       P- addition of hydrogen
16.   
    1. Soap. 1mk
    2. Concentrated NaCl/ Brine/ NaCl(l) 1
    3. To precipitate out the soap 1
17.   
    1. sodium
       Potassium
    2. silver
       Mercury
    3. 2Ca(NO₃)₂ → 2CaO + 4NO₂ + O₂
18.   
    1.  increases;1/2mk because it combines with oxygen to form the solid copper (II) oxide;1mk
    2. Reduces;1/2mk because it combines with oxygen to form the gaseous sulphur( IV) oxide;1/2mk which escapes;1/2mk
19.  
    1. it is the minimum amount of energy required to remove an electron from the outermost energy level of an atom in its gaseous state
    2. C because it requires a lot
20.  
    1. Hydrogenchloride
    2. it prevents sucking back/increases surface area for dissolving
    3. the pH of the water drops
21.  
    1. U- Nitrogen(I)oxide
       W- Nitrogen(iv)oxide
    2. F-ammonium sulphate
       V-ammonium nitrate
    3. NH_3(g) + H₂SO_4(g) → (NH₄)2SO₄
22.   
    1.      
                
    2. It forms a molecular structure with weak vander waals forces that are easily broken √ ½
23. C₂H_4(g) + 3O_2(g) → 2CO_2(g) + 2H₂O_(g)
    1 Mol 3 Mol : 2 Mole (1/2 mks)
    1 Mole: 3 Vol. :2 Vol.
    15cm3 :45cm3 :30 cm3
    Total residual gas mixture = 5cm3 of excess oxygen + 30 cm3 of Co2
    Total = 35cm3 (1/2 mks)
24.        
    1. volume is inversely proportional to pressure
    2. P1V1 =P2V2
       3 x 1 =2 x V2
       V2 =1.5litres
25.  
    1. it is water that contains dissolved calcium and magnesium ions and does not lather easily
    2. Ca(HCO₃)_(aq) → CaCO_3(s) +CO_2(g) +H₂O_(l)
    3.      
       • contains calcium ions required for strong teeth
       • used for brewing
       • used for leather tanning
26.   
    1. to generate steam that reacts with zinc metal and also drive away air from the apparatus
    2. zinc glows and a yellow solid is seen
27.  
    1. 2PbS_(s) +3O_2(g) → 2PbO_(s) +2SO_2(g)
    2. Carbon(iv)oxide
    3. making lead pipes, making lead acid batteries
28.    
    1. (CH₂)n = 42
       (12 + 2)n = 42
       14n = 42
       n = 3 √ ½
       MF = 3(CH₂) C₃H₆ √ ½
    2. CnH₂n √ 1
    3. But-1-ene/ √ ½/ Butene