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

INSTRUCTIONS TO CANDIDATES

• Answer all the questions.
• Mathematical table and electronic calculators may be used
• All workings must be clearly shown where necessary
• Answer all questions in English.

1. The products formed by the action of heat on carbonates A,B, and C are shown below.
   

   Carbonates	Products Fromed
   A	Metal Oxide + Carbon (IV) Oxide
   B	Metal, Oxygen and Carbon (IV) Oxide
   C	No product

   1. Arrange the metals in order of reactivity starting with the most reactive. ( 2 mks)
   2. Which of the carbonate is soluble in water? (1 mk)
2. Samples of urine from three participants E, F and G at a national police recruitment exercise were spotted onto a chromatography paper alongside two illegal drugs D1 and D2. A chromatogram was run using ethanol. The diagram below shows the chromatogram.
         
   
   1. Identify the participant who had used an illegal drug. (1 mk)
   2. Which drug is less soluble in ethanol? (1 mk)
3. Describe a simple laboratory experiment that can be used to distinguish between Sodium sulphite and Sodium Sulphate. (3 mks)
4. Explain why burning Magnesium ribbon continues to burn in a gas jar full of sulphur (iv) Oxide while a burning wooden splint would be extinguished. (3 mks)
5. Study the arrangement below and answer the questions that follow
   
   State and explain what will be observed after sometime. (2 mks)
6. Study the diagram below and answer the questions that follow.
         
   
   1. Identify reagent X. (1 mk)
   2. Draw the structural formula of gas Y. (1 mk)
   3. What name is given to the process that takes place in step 5? (1 mk)
7. Describe a laboratory experiment that can be used to obtain aluminum chloride from a mixture of sodium chloride and aluminum chloride. (2 mks)
8. The graph below shows the solubility curves for salts J and K.
   
   Which of the two salts is more soluble in water? Explain (2 mks)
9. The electronic configuration of the ions of L2⁺ and M - are 2.8 and 2.9 respectively
   1. Write the electronic configuration of atoms of element L and M. (1 mk)
   2. Write the formula of the Oxide of L ( 1 mk)
   3. Compare the atomic radius of the element M and the ionic radius of ion M - (1 mk)
10. Iron roofing sheets are coated with zinc as “Sacrificial” metal.
    1. Give the name of the process by which iron sheets are coated with zinc. (1 mk)
    2. Give a reason why copper is not used as “ sacrificial” metal in the process you have named in (a) above. (2 mks)
11. The empirical formula of a hydrocarbon is C 2 H 3 . It has a molecular mass of 54.
    1. Determine the molecular formula of the hydrocarbon. (1 mk)
       ( C= 12, H= 1)
    2. Draw the structural formula and name the hydrocarbon. (2 mks)
12. Write chemical equations to show the difference between the bleaching action by chlorine and bleaching action by sulphur (IV) Oxide gases. (2 mks)
13. Elements Q and R have atomic numbers 12 and 17 respectively.
    1. Which element is a metal. (1 mk)
    2. Which dot(.) and (x)cross to represent electrons, show the bonding between Q and R in the compound of the elements.  (2 mks)
14. Study the set- up below and answer the questions that follow:-
    
    
    1. What is the role of hydrated copper (II) Sulphate in the set- up. (1 mk)
    2. Identify Gas S? (1 mk)
    3. Write a chemical equation for the reaction taking place in the combustion tube. (1 mk)
15. Calculate the number of aluminum ions in 250 cm 3 of 0.1 M aluminum sulphate.
    ( Avogadro’s Constant = 6.0 x10²³ ) (3 mks)
16. The table below shows solutions and their PH values.
    

    Solution	pH Value
    T	1.5
    U	7.0
    V	14.0

    1. Select any pair that would react to form a solution of PH 7. (1 mk)
    2. Identify two solutions that would react with Alluminium hydroxide. Explain your answer. (2 mks)
17. Name two allotropes of carbon. (2 mks)
18. 20cm³ of gas W takes 12.6 seconds to pass through a orifice. 10cm³ of Oxygen gas takes 11.2 seconds to diffuse through the same orifice under same conditions of temperature and pressure calculate the molecular mass of gas W.   (2 mks)
19. The diagram below shows an incomplete set- up of the laboratory preparation of dry carbon (IV) Oxide. Complete the diagram. (3 mks)
    
20. State three uses of Argon (3 mks)
21. The table below shows the results obtained when halogens are bubbled into a test tube containing solutions of halides labeled A, B and C. A tick ( ✓ ) means reaction takes place and (x) no reaction occurs.
    

    Halogen	Halide ion in solution
    	A	B	C
    12	X	X	X
    Br2	X	✓	X
    Cl2	X	✓	✓

    1. Identify the halide ions represented by letters A,B,and C (1 ½ mks)
    2. State the colour change for the reaction between chlorine and iodide ions and write an ionic equation for the reaction. (1 ½mks)
22. In one of the dry practicals assignment to analyze cation a salt, the following observations were made:
    

    	Test	Observation	Inference
    (i)	NaOH dropwise till in excess	White ppt formed soluble in exces
    (ii)	NH3 solution dropwise till in excess.		Presence of Zn2+ ions confirmed.

    1. Fill in the blanks in the table above. (2 mks)
    2. Give an ionic equation for the reaction that occurs in test (ii) when excess NH₃ solution is added.
       (1 mk)
23. Describe how you would prepare a pure sample of lead (II) carbonate starting with lead (II ) oxide. (3 mks)
24. Explain how sodium hydrogen carbonate and ammonium chloride are separated in solvey process.
    (2 mks)
25.  
    1. What is fuel? (1 mk)
    2. Firewood is the main source of fuel in most Kenyan homes. State two effects of wood products of burning fuel on environment. (1 mk)
26. Calculate the mass of Calcium Oxide that can be obtained from 30g of calcium carbonate if completely decomposed by strong heating.  (3 mks)
    ( Ca =40 , C=12, O=16)
27. State the two ions that causes hardness in water. (1 mk)
28. Below is a table giving solubility a substance A and B at 20°C and 50°C
    

    Suubstance	Solubility	100g of water
    	20°C	40°C
    A	40	65
    B	15	17

    When aqueous mixture containing 55g of A and 12g of B at 80°C was cooled to 20°C crystals were formed
    1. Identify the crystal formed (1 mk)
    2. Determine the mass of the crystals formed (1 mk
    3. Name the method use dot obtain the crystals (1 mk)
29. The diagram below shows sodium metal being dropped in water. Study it and answer the questions that follow;
               
    
    1. State and explain two observations made during the reaction. (2 mks)
    2. Write an equation for the reaction that takes place during the experiment. (1 mk)
30.  
    1. In an experiment to determine solubility of solid P in water at 25°C, the following results were obtained.
       Mass of empty evaporating dish – 24.2g
       Mass of evaporating dish + saturated solution = 40.4g
       Mass of evaporating dish + dry solid P = 28.4g
       Using the information above calculate the solubility of solid Pat 25°C in g/100g of water.  (2 mks)
    2. State one precaution observed when carrying out the experiment in (i) above (1 mk)

MARKING SCHEME

1.  
   1.        Most reactive
                               (2mks)
   2. Carbonate C is soluble in water                                                                                 (1mk)
2.  
   1. F                                                                                                                                 (1mk)
   2. D₁                                                                                                                                (1mk)
3. To Sodium sulphate add barium chloride if precipitate forms add dilute Hcl . If the substance is Na₂ SO₃ the precipitate dissolves. If the same treatment is given to Na₂SO₄ a white precipitate forms but insoluble in dilute HCl              ( 3mk)
4. A burning magnesium flame decomposes SO₂ to form Sulphur and Oxygen. Oxygen reacts with Mg to form MgO. Wooden splint flame burns at a low temperature not hot enough to decompose SO_2.                                                                                                                                                                                                                    (3mks)
5.  
   • Candle goes off since all oxygen is used up✓.1
   • Lime water forms white precipitate due to ✓1 the evolved from combustion of candle wax.  (2mk)        
6.  
   1. Water ✓1
   2. H – C Ξ C – H ✓1
   3. Polymerisation ✓1
7. Heat to mixture ✓½ a beaker covered with a watch glass with water ½ in it. AlCl₃  Sublimes ✓ ½ and deposits at the base of the watch glass. Sodium chloride remains ½ in the beaker as residue.                                                                                                ( 2mks)
8. Salt J ✓1 . Its solubility increases with increase temperature ✓1.                                          (2mks)
9.  
   1.  
      1. L = 2.8.2 ✓½
      2. M= :2.7✓½                                                                                                                (1mk)
   2. LO ✓1
   3. Atomic radius of element M is less than ionic radius of M­^-,✓1                               (1mk)
10.  
    1. Galvanization
    2. Copper is less reactive than ion. Copper will not corrode. Iron rust instead of copper.
11.  
    1. (C₂H₃)x = 59 ✓½
       24 x 3x =54
       27x = 54
       X= 2. ⇒ ( C₂H₃)2
       Molecular formula = C₄ H₆ ✓½
    2.   
       
                          2 mentylpropane
       (Any one of the above structures and name)
12. HOCl_(aq) + Dye   →   HCL (_aq) + dye [O] ✓1
    H₂SO₃ + dye (O)   →   H₂SO₄ + dye ✓1
13.  
    1.  
       1. Q   ✓ ½
       2. R   ✓ ½ 
    2.   
       
14.  
    1. Produce stream ✓1
    2. Hydrogen ✓1
    3. Mg_(s) + H₂O_(g)  →  MgO _(s) + H _{2 (g)}✓1
15. Moles of AlCl₃ in 250 cm³ 
    250 × 0.1 = 0.025✓1
        1000
    AlCl₃ (aq) →   Al³⁺_(aq) + 3c ( 1am) ✓1
    Moles of Al³⁺ in 250 cm³
    0.0250 x 1 = 0.025 moles ✓½
    Number of Al³⁺ = 0.025 x 6.0 x 10²³
    = 1.5 x 10²² ions ✓ ½
16.  
    1. T and V✓1
    2. T and V ✓1 Al (OH) ­₃ is amphteric hydroxide ✓1
17.  
    • Graphite ✓1
    • Diamond ✓1
18. 20 cm³ of W takes   → 12.6 sec
    ∴ 10cm³ of W  → 10 × 12.6 = 6.3 seconds
                                       20                      
    
    0.5625²  = ^Mw/₃₂
    Mw = 0.5625² x 32= 10.125g. ✓1
    Accept any other method which is correct.
19.   
    
20.  
    • Argon is used in ore welding.
    • Used in electrical light bulb
    • Used in the production of titanium
    • Used in growing of crystals of silicon and germanium.
      ( any threes uses 1mk each)
21.  
    1.  
       1. A-Cl^-   ( Chloride Ion) ✓ ½
       2. B – I^-   ] ( Iodide Ion) ✓ ½
       3. C – Br_­­^‑           ( Bromide Ion) ✓½                                                          ( 1 ½ mks)
    2. The solution turns from colourless to black ✓½  2I _(aq)+ Cl _{2 (g)}      2C^-_Aq) + I _{2 (aq)}
22.  
    1. Al³⁺; Zn²⁺, Pb²⁺ present✓1
       White ppt formed soluble in excess✓1
    2. Zu (OH)_{2 (s)}  + 4NH_{3 (g)}      [Zu (NH₃)₄] ²⁺_(aq)  + 2OH^-_(aq) ✓1
23.  
    • Measure 20cm³ of HNO₃ and place it in a beaker.
    • Add lead (II) Oxide until excess✓ ½
    • Filter off the lead (II ) nitrate formed ✓1/2 and transfer the filtrate in a clean beaker.
    • Add a solution of sodium carbonate to lead T ½ (II) nutrate a white precipitate forms which is lead (II) carbonate ✓2
    • Filter off the precipitate and was it with distilled water than to dry the residue between dry filter paper.
24. Separation is done by filtration ✓1 NaHCO₃ is less soluble at low temperature .NH₄cl is more soluble at low✓ temperatures. NaHCO₃ crystal form and filtered off.
25.  
    1. Fuel is a substance which releases energy when burned.                                                 ( 1mk)
    2. Carbon in ✓½ firewood when burnt in insufficient air ✓½  forms CO✓. The gas is poisonous when
       ✓ ½ breathed in and leads to death carbon ( iv) Oxide is also formed. This gas can form acid rain and causes global warming.                                                                                  (2mks)
26. Ca CO_3(s)         CaO_(c)   + CO_{2 (g)✓} 1
    40 + 12 + 48 ✓½       40+16 ½  40+1 ✓½
            100g                          56g
    If 100g of CaCO₃ produce 56 g of Ca✓½ O
     ∴ 30g of CaCo₃ (30 × 56)  = 16.8g ✓½
                                                    100              
27.  
    • Calcium Ions ✓1
    • Magnesium ✓1
28.  
    1. Substance A. ✓1
    2. 55 – 40 = 15g ✓1
    3. Fractional crystallization ✓1
29.  
    1.  
       • Hissing sound produced due to the production of hydrogen gas. ✓1
       • Darts on the surface of water because hydrogen produced propels it. ✓1
       • Melts into a silvery ball because of the heat produced during the reaction.
       • Floats on the water because its less denser than water (mark any two correct)
    2. 2Na_(s) + 2H₂O_(l) → 2NaOH_(aq) + H_2(g) ✓1
30.  
    1. Mass of solute =  28.4 – 24.2
                                = 4.2
       Mass of water    = 40.4 – 28.4 ✓1
                                 = 12
       Solubility            = 4.2 x 100
                                          12
                               = 35g/100gm ✓1
    2. Ensure that no solid is lost during evaporation ✓1