Chemistry Paper 1 Questions and Answers - Kapsabet Mock Exams 2021/2022

INSTRUCTIONS TO CANDIDATES:

1. Write your name and index number in the spaces provided above.
2. Sign and write the date of examination in the spaces provided above.
3. Answer ALL the questions in the spaces provided.
4. Mathematical tables and silent electronic calculators may be used.
5. All working must be clearly shown where necessary.
6. Candidates should check the question paper to ascertain that all the pages are printed as indicated and that no questions are missing

1. The samples of equal volumes of water were put in 100cm3 conical flasks and heated for 5 minutes on a Bunsen flame. It was observed that sample 1 registered a low temperature than sample II
   
   
   1. Name flame I (1mk)
   2. State one disadvantage of using flame I for heating (1mk)
2. Study the diagram below and answer the questions that follow.
   The diagram shows the method used to separate component of mixture P
   
   
   1. Name X (1mk)
   2. What is the name given to the method used in separation of mixture P (½mk)
   3. What would happen if the inlet and outlet of water were interchanged ( ½mk)
   4. Which physical property is used to separate mixture P (1mk)
3. The table below shows the solubility of three solids P, Q, and R.
   

   Solid	Cold Water	Hot Water
   P	soluble	soluble
   Q	insoluble	insoluble
   R	insoluble	soluble

   How would you obtain pure samples of R,P and Q (2mks)
4. State why a water molecule H2O can combine with H+ ion to form H3O+ ion (1mk)
5. The P^H values of some solutions are given below
   

   PH	14.0	1.0	8.0	6.5	7.0
   Solution	M	L	N	P	Z

   1. Identify the solution with the lowest concentration of hydrogen ion. Give reason for your answer (1mk)
   2. Which solution would be used as an anti-acid for treating stomach upset. Give for your answer (1mk)
6. The data below gives the electronic configuration of some selected atoms and ions
   

   Atom/ion	A2+	B	C2-	D2+	E	F-	G+	H
   Electronic configuration	2	2.4	2.8	2.8.8	2.8	2.8.8	0	2.8.2

   1. Select an atom that is a noble gas (1mk)
   2. What is the atomic number of C and A (1mk)
   3. Select an element that belong to group 2 and period four (1mk)
   4. Write the formula of the compound formed when D and F react (1mk)
7. Helium is used instead of hydrogen in balloons for metrological research. Explain (1mk)
8. Zinc metal and hydrochloric acid reacts according to the following equation
   Zn(s) + 2HCl_(aq) ZnCl_2(aq) + H_2(g)
   1.96g of Zinc metal were reacted with 100cm3 of 0.2M hydrochloric acid
   1. Determine the reagent that was in excess (2mks)
      Zn=65.2; Molar gas volume at s.t.p 22.4 liters
   2. Calculate the total volume of hydrogen gas that was liberated at s.t.p (1mk)
9. Give the IUPAC names of the following compounds (1mk)
   1. CH₃CH₂CH₂CH CH₃
      CH₃ …………………………………………………………………………….
   2. CH₃CH=CHCl …………………………………………………………………………… (1mk)
10. 0.9g of potassium chloride and potassium carbonate mixture completely reacted with 25cm³ of 0.2M hydrochloric acid
    1. Write an equation of the reaction which takes place (1mk)
    2. Determine the number of moles of the acid used (1mk)
    3. Calculate the mass of potassium chloride in the mixture (K=39.0; C=12.0; O=16.0) (2mks)
11. Study the flow chart below and answer the questions that follow
    
    
    1. Identify metal M: ………………………………………………………. (1mk)
    2. Colourless gas: …………………………………………………………. (1mk)
    3. Write an equation that leads to the formation of white precipitate in process (1mk)
12.      
    1. Define the term dynamic equilibrium (1mk)
    2. A reaction at equilibrium can be represented as
       2CrO^2-_4[aq] +2H⁺[aq]  Cr₂O7²_[-aq] + H₂O_{l}
       Yellow                            orange
       State and explain the observation made when NaOH is added to the equilibrium mixture (2mks)
13. Few drops of hydrochloric acid were added into a test tube containing lead {II} Nitrate solution
    1. State one observation made (1mk)
    2. Write an ionic equation of the reaction that occurred in the test tube (1mk)
14. A compound of carbon, hydrogen and oxygen contains 57.15% carbon, 4.76% hydrogen and the rest oxy gen. If its relative molecular mass is 126, find its molecular formula. (C = 12, H = 1, O = 16) (3mks)
15. Study the information in the table below and answer the questions that follow.
    

    Salt	Solubility g/100g of water
    	At 40°C	At 60°C
    CuSO4	28	38
    Pb(NO3)2	79	98

    A mixture containing 35g of CuSO₄ and 78g of Pb(NO₃)₂ in 100g of water at 60°C was cooled to 40°C.
    1. Which salt crystallized out? Give a reason. (2 marks)
    2. Calculate the mass of the salt that crystallized out. (1 mark)
16.    
    1. Distinguish between strong and concentrated acid ( 1mk)
    2. A solution of ammonia in methylbenzene has no effects on red litmus paper while a solution of ammonia in water turns red litmus paper blue. Explain (2mks)
17. Name the process which takes place when
    1. Iodine changes directly from solid to gas (1mk)
    2. Fe2+( aq) changes to Fe3+(aq) (1mk)
    3. White sugar changes to black when mixed with concentrated sulphuric (VI) acid (1mk)
18. In the last stage of the solvay process, a mixture of sodium hydrogen carbonate and ammonium chloride is formed
    1. State the method of separation used (1mk)
    2. Write an equation showing how lime is slaked (1mk)
    3. Name the by- product recycled in the above process (1mk)
19. The diagram below is a section of a model of the structure of element K
    
    
    1. State the type of bonding that exist in K (1mk)
    2. In which group of the periodic table does element K belong. Give a reason (2mks)
20. Study the diagram below and answer the questions that follow
    
    
    1. State two observations made in the above experiment when sodium react with water (2 mks)
    2. Write a chemical equation for the reaction that takes place (1mk)
21.      
    1. Explain why permanent hardness in water cannot be removed by boiling (2mks)
    2. Name two methods that can be used to remove permanent hardness from water (1mk)
22. Write an equation to show the effect of heat on the nitrate of: - (2mks)
    1. Potassium
    2. Silver
23. Study the diagram below and use it to answer the questions that follow.
    
    
    1. State the observation made in the combustion tube. (1mk)
    2. Write an equation for the reaction that took place in the combustion tube. (1mk)
    3. Name gas P
24. Sulphur exists in two crystalline forms.
    1. Name one crystalline form of Sulphur. (1mk)
    2. State two uses of Sulphur. (2mks)
25. Bond energies for some bonds are tabulated below: -
    

    BOND	BOND ENERGY KJ/mol
    H-H	436
    C=C	610
    C-H	410
    C-C	345

    Use the bond energies to estimate the enthalpy for the reaction. (3mks)
    C₂H_4(g) + H_2(g) → C₂H_6(g)
26. Study the set up below and answer the questions that flows
    
    State all the observations that would be made when the circuit is completed (3mks)
27. Describe how solid samples of salts can be obtained from a mixture of lead (II) chloride, sodium chloride and ammonium chloride. (3mks)
28. The diagram below represents a set-up used to prepare oxygen gas.
    
    
    1. Name substance Q. (1mk)
    2. Complete the set-up to show how oxygen gas is collected. (1mk)
    3. Write the equation for the reaction that occur. (1mk)
29. Two reagents that can be used to prepare chlorine gas are potassium manganate (VII) and hydrochloric acid.
    1. Write an equation for the reaction. (1mk)
    2. Give the formula of another reagent that can be used instead of potassium manganate (VII). (1mk)
    3. Using an equation illustrate how chlorine bleach coloured substances. (2mks)

MARKING SCHEME

1.      
   1. Luminous flame 1mk
   2. Produces less heat
      or
      Blackens the conical flask/ sooty 1mk
2.    
   1. Fractionating column ½ mk
   2. Fractional distillation ½ mk
   3. Condensation would not occur 1 mk
   4. Differences in boiling points 1mk
3.    
   • Dissolve the mixture in hot water ½ mk
   • Filter the solution to remove insoluble solid Q as a residue ½ mk
   • Cool the filtrate. R crystallizes and is removed by filtration ½ mk
   • Evaporate the latter filtrate to obtain P ½ mk
4. H₂O has lone pairs of electrons which can be shared with H+ ion 1mk
5.      
   1. Solution P ½ Weak acid ½ mk
   2. Solution N ½ Weak base ½ mk
6.    
   1. E 1 mk
   2. C=8 ½ mk
      A=4 ½ mk
7. Helium is inert (unreactive) ½ while hydrogen is reactive ½ mk
8.      
   • Moles of zinc=1.96 =0.03 ½ mk
                            63.5
   • Moles of HCL 100 x 0.2 =0.02 ½ mk
                               1000
   • Moles of zinc reacted 0.02 =0.01 ½ mk
                                          2
     Zinc is in excess ½ mk
   • Mole ratio of HCL: H₂ 2:1
     Moles of H2 (g) produced = 0.02 = 0.01 moles ½ mk
                                                   2
   • Volume of H₂ g at S.T.P= 0.01x22.4
     = 0.224 dm³
     or 224cm³ ½ mk
9.      
   1. 2, methyl pentane 1 mk
   2. 1- chloro propene 1 mk
      1. To prevent oxidation of magnesium ribbon 1 mk
         To generate steam 1 mk
      2. Mgs + H₂O(l) → MgO(s) + H_2(g) 1 mk
         Should be balanced with state symbols
10.      
    1. K₂ CO_3(s) + 2HCl_(aq) → 2KCl_(aq) + CO_2(g)+ H₂O(l) 1 mk
       Should be balanced with state symbols
    2. Moles of acid 25x0.2
                               1000
       =0.005 moles ½ mk
       Moles of K2 CO3 = 0.005
                                         2
       =0.0025 moles ½ mk
    3. RFM of K₂CO₃ = 138 ½ mk
       Mass of K₂CO₃ in the mixture
       138 x 0.0025= 0.345g ½ mk
       Mass of KCL in the mixture
       0.9-0.345
       = 0.555g ½ mk
11.    
    1. Zinc 1 mk
    2. Hydrogen 1mk
    3. Zn²⁺ + 2OH-_(aq) → Zn(OH)_2(s) 1mk
12.    
    1. Dynamic equilibrium is attained when the rate of the forward reaction is equal to that of the reverse reaction 1mk
    2. The intensity of the yellow colour in the equilibrium mixture increased 1mk.
       Additional of NaOH reduces the concentration ofH+ ions hence equilibrium shifts to the left 1mk
13.      
    1. White precipitate was formed 1mk
    2. Pb²⁺_[aq] + 2Cl- [aq] → PbCl₂[s] 1mk
14.      
    

    Element	C	H	O
    % Composition	57.15	4.76	38.09
    r.a.m	12	1	16
    %    R.A.M	4.7625	4.76	2.380625
    Moles Ratio	4.7625   = 2.004 = 2 2.380625	4.76     = 2.00 2.380625	2.380625 = 1 2.380625

    Empirical formula= C₂H₂O√ ½
    n = 126 = 3 √ ½
           42
    Molecular formula = (C₂H₂O)₃ = C₆H₆O₃√ ½
15.      
    1. Copper(II) sulphate;√ 1 at 40ºC ONLY 28gm is soluble leaving the rest undissolved. √ 1
       At 40ºC, all lead nitrate dissolves.
    2. 35-28√ ½=7g√ ½
16.    
    1. Strong acid ionizes completely in solution while concentrated acid contain high number of acid molecules per given volume. 1mk
    2. Ammonia in water dissociate to produce hydroxide ion √ 1while in methybenze it remain in molecular form. √ 1
17.    
    1. Sublimation √ 1
    2. Oxidation √ 1
    3. Dehydration √ 1
18.    
    1. Filteration√ 1
    2. Ca(OH)_(s) + H₂O_(l) → Ca(OH)_2(aq) √ 1
    3. Carbon(IV) oxide// Ammonia√ 1
19.    
    1. Metallic bond√ 1
    2. Group I√ 1; Has one delocalized electron from each atom√ 1
20.      
    1. Melts into a silvery ball√ 1/darts on the surface of water√ 1/Floats on the surface of water/hissing sound ( any two)
    2. 2Na(s)+ H₂O_(l) → 2NaOH_(aq) + H_2(g) √ 1
21.    
    1. Permanent hardness is caused by the presence of MgSO₄/ CaSO₄/CaCl₂ √ 1which do not decompose on heating√ 1
    2. Addition of Sodium Carbonate√ ½/ammonium hydroxide√ ½/ Ion exchange (any two)
22.    
    1. 2KNO_3(s)  2KNO_2(s) + O_2(g)
    2. 2AgNO_3(s)  2Ag_(s) + 2NO_2(g) + O_2(g) 
23.    
    1. A brown solid is formed 
    2. CuO_(s) + C_(s)  Cu_(s) + CO_(g) 
    3. Carbon (II) Oxide. 
24.    
    1. Rhombic or monoclinic Sulphur.
    2.    
       • For hardening rubber
       • Manufacture of sulphuric acid  (Any two correct)
       • As a fungicide
       • In making calcium hydrogen sulphite used in bleaching.
25. Bond breaking
    4 C-H - 4x410 = 1640
    C=C - 1x610 = 610
    H-H - 1x436 = 436
    +2686
    ΔH = +2686 - 2805
    = -119kJ/Mol
    Bond formation
    6C - H 6x410
    =2460
    C-C- 3 45
    -2805
26.    
    • The bulb lights √ 1
    • Grey solid deposits at the cathode √ 1
    • Brown gas bubbles produced at the anode √ 1
27.    
    • Heat to sublime NH₄Cl. ½
    • Add water ½ to dissolve NaCl. ½
    • Filter ½ the residue is PbC_l2 ½
    • Evaporate ½ the filtrate (NaCl solution) to obtain NaCl solid
28.    
    1. Sodium peroxide 
    2.  
         
    3. 2Na₂O₂(S) + 2H₂O(l) → 4NaOH_(aq) + O_2(g)
29.      
    1. 2KMnO₄(S) + 16HCl_(aq) → 2KCl_(aq) + 2MnCl_2(aq) + 8H₂O(l) + 5Cl_2(g) 
    2. MnO₂ 
    3. Cl_2(g) + dye + H₂O_(l) → 2HCl_(aq) + (dye – O)