Chemistry Paper 1 Questions and Answers - Cekana Mock Exams 2023

INSTRUCTIONS

• Write your name and index number in the spaces provided above
• Sign and write date of examination in the space provided.
• All working must be clearly shown where necessary.
• Mathematical tables and silent electronic calculations may be used
• Answer all questions in English.

QUESTIONS

1. Give two difference between a thistle funnel and a dropping funnel (2marks)
2. Gives names of the following processes used to
   1. Separate calcium carbonate from water (1mark)
   2. Separate a mixture of nitrogen and Helium (1mark)
3. The table below shows some solutions and their pH value
   Solution           pH values
   P                      1.5
   Q                      6.0
   R                      14.0
   S                       8.0
   Which of the above solutions is likely to be of
   1. Sodium carbonate (1mark)
   2. Solution with high concentration of Hydrogen ions (1mark)
4. In the laboratory preparation of oxygen gas, Hydrogen peroxide is used.
   1. Name the catalyst used (1mark)
   2. Write a balanced chemical equation for the reaction (1mark)
5. State three observation made when a piece of potassium metal is dropped into cold water giving a reason for each. (3marks)
6. In the extraction of iron, the iron ore is reduced to iron in a blast furnace
   1. Name the main ore used in extraction of iron (1mark)
   2. What is the main reducing agent in the blast furnace (1mark)
   3. Write the equation for the reaction through which the iron ore is reduced to iron in the blast furnace (1mark)
7. Draw the structure of the following
   1. Mg⁺ (1mark)
   2. Hydroxonium ion (1mark)
8. When 27.8g of hydrated aluminium oxide (AI2O3•XH2O) was heated to a constant mass 20.6 g of aluminium oxide was obtained. Determine the value of X (Al=27, O=16, H=1 (3marks)
9. In the haber process, the industrial manufacture of ammonia is given by the following equation
   N_2(g)+H_2(g)  2NH_3(g)ΔH=-97KJ/mol 
   1. Name one source of nitrogen gas used in this process (1mark)
   2. Name the catalyst used in the above reaction (1mark)
   3. What is the effect of increasing temperature on the yield of ammonia? Explain (2marks)
10. Describe the correct process of heating a liquid in a test-tube using a bunsen burner. (3marks)
11. Draw a labelled diagram of a set up that can be used to prepare dry sample of carbon (IV) oxide using calcium carbonate (3marks)
12.  
    1. Draw structural formulae of two positional isomers with molecular formula C₄H₈ (2marks)
    2. Study the equation below and answer the questions that follow
       C₆H₁₄+CL₂-C6H₁₃CL+HCL
       1. State the condition under which this reaction occurs (1mark)
       2. Give the general name of this type of reaction (1mark)
13.  
    1. Define hydration energy (1mark)
    2. Given that the lattice energy of NaCl is +781kJ/mol and hydrated energy of Na⁺ and Cl^- are
       -390kJ/mol and -384kJ/mol respectively. Calculate the heat of solution of one mole of NaCl_(s) using energy cycle. (3marks)
14. 240cm³ of nitrogen (I) oxide gas takes 16 seconds to diffuse through a certain porous pot. 300cm³ of x takes 12 seconds to diffuse through the same pot calculate the relative molecular mass of gas x. (N=14, O=16) (3marks)
15. Draw a well labelled diagram that can be used during electrolysis of molten sodium chloride in the laboratory (3marks)
16. The figure below describes the manufacture of detergent B
    
    
    1. What type of detergent is B (1mark)
    2. Draw the structure of detergent B (1marks)
    3. State two disadvantage of using detergent B (2marks)
17. Use the flow chart below to answer the question below
    
    
    1. Explain the observation in step II (1mark)
    2. Name the process that takes place when flower petals are put into solution T (1mark)
    3. Reaction in step I takes place only in presence of moisture. Give a reason for this (1mark)
18. The diagram below represent a dry cell with Zinc can and graphite as the electrodes and ammonium chloride paste as an electrolyte
    
    
    1. Write an ionic equation for the reaction taking place at
       1. Anode (1mark)
       2. Cathode (1mark)
    2. State the property of carbon powder that make it suitable for use in the cell (1mark)
    3. State one other substance that could be used in place of manganese (IV) oxide (1mark)
19. The diagram bellow represents part of periodic table. Use it to answer the question that follow
    
    
    1. Write the electronic arrangement for the stable ion formed by X (1mark)
    2. Write an equation for the reaction between W and Q (1mark)
    3. Compare the ionization energy of element A and Z. Explain. (2marks)
20. Write equations to show the effect of heat on each of the following
    1. Ammonium nitrate (1mark)
    2. Potassium nitrate (1mark)
    3. Anhydrous iron (II) sulphate (1mark)
21. When excess chlorine gas is bubbled through diluted sodium hydroxide solution; the resulting solution act as a bleaching agent
    1. Write an equation for the reaction between chlorine gas and sodium hydroxide solution (1mark)
    2. Name the bleaching agent (1mark)
    3. Write an equation to show the bleaching and explain how it occurs (2marks)
22. Alpha ()and beta (ß) particles can be distinguished using papers, aluminium foil and an electric field complete the diagram below to show how this is done (3marks)
    
23. During electrolysis of magnesium sulphate, a current of 0.3A was passed for 30 minutes calculate the volume of gas produced at the anode (molar gas volume =24dm³ IF=96500C (3marks)
24. Starting with sodium metal, describe how a sample of crystal of sodium hydrogen carbonate may be prepared (3marks)
25. When 20cm³ of 0.5M sulphuric (VI) acid was mixed with 20cm³ of 1M NaOH, the temperature of the solution rose from 24.0°C to 32.0°C calculate the molar heat of neutralisation (Specific heat capacity of the solution is 4.2Jg^-1density is 1g/cm³ (3marks)
26. The table below shows the test carried out on a sample of water and results obtained
    

    Sample	Test	observation
    A	Addition of NaOH solution drop wise until in excess	White precipitate souble in exess
    B	Adding of NH3(aq) solution	White precipitate
    C	Addition of dilute HNO3 followed by Ba(NO3)2	White precipitate

    
    
    1. Identify the anion present in the water (1mark)
    2. Write the ionic equation for the reaction in C (1mark)
    3. Write the formula of the complex ion in A (1mark)

MARKING SCHEME

1.  
   • A thistle funnel has no tap while dropping funnel has a tap
   • A dropping funnel allows one to add controlled amount of solution while thistle funnel does not
2.  
   1. Filtration
   2. Fractional distillation
3.  
   1. S
   2. P
4.  
   1. manganese (iv) oxide
   2.  2H₂O_2(I) ^{→ MnO₂} 2H₂O_(I)O2_(g)
      (penalise ½ for wrong or missing state symbol
      Penalise fully if not balanced
5.  
   • Potassium will float  ½- less dense than water.½
   • Potassium will melt into a silvery½ ball since reaction exothermic.½
   • Produces a hissing sound½ - hydrogen gas produced½
   • A lilac (purple)½ flame is produced due to production of potassium½ vapour
     Any 3 for 3 marks
6.  
   1. Haematite 
   2. Carbon (ii) oxide / Co     Accept name or formula
   3. Fe₂O_3(x)+3CO_(g)→2Fe_(I)+3CO_2(g)
      or
      2Fe₂O_3(x)+3C_(x)→4Fe_(I)+3CO_2(g)
7.  
   1.   
      
   2.   
      
8. AI₂O₃       H₂O
   20.6      7.2
   102        18
   20.6      7.2
   102       0.4
   0.02      0.4
   1      :    0.02
                   20
   AI₂O₃ •  20H₂O
9.  
   1. Fractional distillation of air/air
   2.  Finely divided iron/iron 
   3. The yield decreases.
      The forward reaction is exothermic hence backward reaction is favoured
      (the decomposition of ammonia)
10. Using a test tube holder
    Slanting 
    Facing away
    Heat
    Rotate
11.  
     
    Workability – 1
    Labelling – 1
    Method of collection -1 – downward delivery or use of syringe.
12.  
    1.   
       
    2.  
       1. u.v light
       2. Substitution
13.  
    1. Hydration energy – energy change that occurs when one mole of gaseous ions becomes hydrated.
    2.   
       
       Total hydration energy =(-390)+(+384)
       ΔH_soin =+781+(-774)=+7KJ/mol
14.   240→N₂O-16sec
    300→N₂O→^300×16/ ₂₄₀
    =20sec
    
    (¹²/ ₂₀)2 = ^M_x/ ₄₄
    0.33=^M_x/ ₄₄
    Mx=44×0.36
    15.84sec 
15.  
     
    Workability 
    Labelling 
    Drawing 
16.  
    1. Soap less detergent
    2.   
       
    3.  
       • It is non-biodegradable hence pollutes the environment.
       • It causes eutrophication
       • It is expensive
17.  
    1. Orange acidified potassium dichromate (VI) changes to green
    2. bleaching
       Moisture assists to form ions for reaction to take place.
18.  
    1. Anode. 
       Zn_(s)→Zn²⁺_(aq)2e^-1
       Cathode. 
       2NH⁺_4(aq)+2e^-→2NH_3(g)+H_2(g)
       2NH⁺_4(aq)+2MnO_2(aq)+2e^-→Mn₂O_3(aq)+2NH_3(g)+H₂O_(I)
    2. it forms a positive terminal of the cell
19.  
    1. 2.8
    2.  3W_(s)+Q_2(g)→W₃Q_2(s)
       3Mg_(s)+N2_(g)→Mg₃N_2(s)
    3. Z has a lower ionization energy than A ,  Z has a larger atomic radius than A hence outermost electron in Z is loosely held.½ 
20.  
    1. NH₄NO_3(s)→N₂O_(g)+2H₂O_(g)
    2. 2KNO_3(s)→2KNO₂+O_2(g)
    3. 2FeSO_4(s)→Fe₂O_3(s)+SO_2(g)+SO_3(g)
21.  
    1. NaOH_(aq)+Cl_(g)→NaCl_(aq)+NaOCl_(aq)+H₂O_(I)
    2. Sodium chlorate (I)1
    3. NaOCl_(aq)+dye→NaCL_(aq)+NaOCL_(aq)+(dye+O)
       NaOcl decomposes to give atomic oxygen (O) that bleaches by oxidation.1
22.   
    
    Angle of deflection 1
    Labelling 1
    Penetration power 1
23.  4OH_(aq)→2H₂O_(I)+O_2(g)+4e
    Q=0.3 × 30 × 60=540e
    Ie=965500C
    4e=386000c
    386000c-24dm3
    540c→^{24 × 540}/ ₃₈₆₀₀₀
    =0.0335 liters
24.  
    • Heat sodium metal (mall pieces) in oxygen to form sodium oxide
    • dissolve the oxide in water to form sodium hydroxide
      (OR) Add a piece of sodium metal to water in a trough to form sodium hydroxide
    • bubble excess CO2 into the solution  to form sodium hydrogen carbonate
    • Warm the solution to concentrate.
    • Allow solution to cool  and form crystals filter and Dry the crystals  between pieces of filter paper
25.  
    mass of solution =(40cm³  1kg/cm³)=40g
    ΔT=32-24=8°C
    ΔH= ⁴⁰/  ₁₀₀₀× 4.2 × 8
    =1.344KJ
    moles of H⁺ ions = ^2(20×0.5)/ ₁₀₀₀ =0.02moles
    0.02moles - ^1.344/₁ × 0.02
    ΔHneut=-67.2KJs/mol
    Penalize ½ for negative sign ½ for wrong or missing units.
26.  
    1. SO^2-₄
    2. Ba²⁺_(aq)+SO^2-_4(aq)→BaSO_4(s)
    3. [AI(OH)₄]^-