CHEMISTRY PAPER 1 - KCSE 2019 BAHATI MOCK EXAMINATION (WITH MARKING SCHEME)

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  1. Distinguish between a thistle funnel and a dropping funnel (1mark)
  2.  
    1. Define an acid. (1 mark)
    2. An ammeter was used to test electrical conductivity of sodium hydroxide and ammonia solution.State and explain the observation made. (2 marks)
  3.  
    1. What name is given to the process by which alcohol is formed from a carbohydrate?(1 mark)
    2. Explain why the solubility of ethane in water is lower than that of (1 mark)
  4. An isotope of Uranium 234-U, decays by emission of an alpha particle to thorium Th-92
    1. Write the equation for the nuclear reaction undergone bythe isotope. (1 mark)
    2. Explain why it is not safe to store radioactive substances in containers made from aluminum sheets.(1 mark)           
  5.  
    1. Methane reacts with oxygen as shown by the equations I and II below:
      1. CH4(g) + 2O2(g) →CO2(g) + 2H2O(l)
      2. 2CH4(g) + 302(g) →2CO(g) + 4H2O(l)
        Which one of the two reactions represents the complete combustion of methane? Explain. (2marks)
    2. 80cm3 of ethane reacted with 150cm3 of oxygen forming carbon (IV) oxide and water. Calculate:
      1. The volume of carbon (IV) oxide formed (1 mark)
      2. The residual air. (1 mark)
  6. The table below gives the atomic numbers of elements W, X, Y, and Z. The letters do not represent the actual symbols of the elements.           
    1. Which one of the elements is least reactive? Explain. (1mark)
    2.  
      1. Which two elements would react most vigorously with each other? (1mark)
      2. Give the formula of the compound formed when the elements in b(i) react. (1mark)
  7. In an experiment to separate a mixture of two organic liquids, liquid M (b.p 56oC) And liquid N (b.p. 118oC), a student set up the apparatus shown below.
    CHEM9DIAG
    1. Identify two mistakes in the set – up. (2marks)
    2. What method would the student use to test the purity of the distillates obtained? (1mark)
  8. When lead (II) nitrate is heated, one of the products is a brown gas.
    1. Write the equation of the reaction that occurs.                       (1 mark)
    2. If 0.290dm3 of the brown gas was produced, calculate the mass of the lead(II)nitrate that was heated.
      (R .F.M of lead (II) nitrate = 331; Molar gas volume = 24dm3).(2marks)
  9.  
    1. Give the name of the process that takes place in step 1. (1mark)
      CHEM7DIAG
    2. Give;
      1. The name of substance G1(1mark)
      2. One use of substance F1(1 mark)
  10. When extinguishing a fire caused by burning kerosene, carbon (IV) oxide is used in preference to water .Explain. (2 marks)
  11. Sulphur burns in air to form sulphur (IV) oxide.A simple energy level diagram for the reaction is given below. Study the diagram and answer the questions that follow.   
    CHEM11DIAG       
    1. What do ΔH3and ΔH1 represent? (1 mark)
    2. Write an expression, for ΔH3 in terms of ΔH1 and ΔH2. (1mark)
  12. Describe how a solid sample of zinc carbonate can be prepared starting with zinc oxide.(3 marks) 
  13. An element X has a relative atomic mass of 88. When a current of 0.5ampere was passed through a fused chloride ofX for 32 minutes 10 seconds, 0.44g of X was deposited.
    1. Determine the charge of element X (1 Faraday = 96500C) (2 marks)
    2. Write the formula of the hydroxide of X. (1 mark)
  14. A hydrocarbon slowly decolorizes bromine gas in the presence of sunlight but does not decolorize acidified potassium permanganate(VII).
    Name and draw the structural formula of the fourth member of the series to which the hydrocarbon belongs. (2marks)
  15. Potassium sulphite solution was prepared and divided into two portions. The first portion gave a white precipitate when reacted with barium nitrate. On addition of dilute hydrochloric acid the white precipitate disappeared.
    1. Write the formula of the compound which formed as the white precipitate. (1mark)
    2. Write the equation for the reaction between dilute hydrochloric acid and the compound whose formula is written in (a) above. (1mark)
    3. What observation would be made if one drop of potassium dichromate solution was added to the second portion followed by dilute sulphuric(VI) acid? (1mark)
  16. A compound of carbon, hydrogen and oxygen contains 57.15% carbon, 4.76% hydrogen and the rest oxygen. If its relative molecular mass is 126, find its molecular formula.
    (C = 12, H = 1, O = 16) (3 mks)
  17. The simplified flow chart shows some of the steps in the manufacture of sodium carbonate by the Solvay process        
    CHEM17DIAG              
    1. Identify substance L (1mark)
    2. Name the process taking place in step II(1mark)
    3. Write an equation for the reaction which takes place in step III.(1mark)
  18. The set – up below was used to study some properties of air.
    CHEM18DIAG
    State and explain two observations that would be made at the end of the experiment. (2 Marks)
  19.  
    1. A sample of water in a beaker was found to boil at 1020C at 1 atmospheric pressure. Assume that the thermometer was not faulty explain this observation (1mk)
    2. Study the information in the table below and answer the questions that follow.

      Salt

      Solubility g/100g of water

      at 40°C

      of 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 crystallised out? Give a reason. (2 marks)
      2. Calculate the mass of the salt that crystallized out. (1 mark
  20. Consider the following reaction at equilibrium.
    PCl5 (g)PCl3 (g) + Cl2 (g)
    Complete the table below to show the effect of different factors on the position of equilibrium. (3mks)

    Factor

    Effect on the equilibrium position

    (i) Decrease pressure

     

    (ii) Removing chlorine

     

    (iii) Adding Helium gas to mixture

     
  21. The set – up below was used to prepare hydrogen gas
    CHEM21DIAG
    1. Complete the diagram to show how a dry sample of hydrogen gas can be collected(3mks)
    2. Write an equation for the reaction, which takes place when hydrogen gas burns in air.(1mk) 
  1. In a certain reaction, 18.7cm3 of a dibasic acid required 25cm3 of 0.1M NaOH for complete neutralization.
    1. How many moles of Sodium hydroxide are contained in 25cm3? (1mk)
    2. Calculate the molarity of the dibasic acid. (2mks)
  2. In an experiment to prepare nitrogen (I) oxide, ammonium nitrate was gently heated in a flask.
    1. Write the equation for the reaction that took place in the flask. (1 mark)
    2. State and explain how the gas was collected.(1 mark)
    3. A sample of the gas was tested with damp blue and red litmus papers. What observations were made? (1mark)
  3. Under certain conditions, chlorine gas reacts with sodium hydroxide to form sodium hypochlorite.
    1. Name the condition under which sodium hydroxide reacts with chlorine to form Sodium hypochlorite.  (1 mark)
    2. State two uses of sodium hypochlorite. (1 mark)
  4.  
    1. Calculate the oxidation state of chromium in the ion Cr2 O2-. (1 mark)
    2. Using oxidation numbers, determine from the equation below the species which undergoes oxidation and reduction.
      2FeCl2(aq) + Cl2(g)→2Fe Cl3(aq)
      Oxidation - (1 mark)
      Reduction - (1 mark)
  5. The table below gives some properties of three elements in group (VII) of the periodic table. Study it and andanswer the questions that follow:

    Element

    Atomic

    No.

    Melting Point

    (0C)

    Boiling Point

    (0C)

    Chlorine  

    17

    101

    -34.7

    Bromine

    35      

    -7

    58.8

    Iodine

    53

    114    

    184


    1. Which element is in liquid form at room temperature? Give a reason.(2 marks)
    2. Explain why the boiling point of iodine is much higher than that of chlorine. (2 marks)
  6. Study the standard reduction potential given and answer the questions that follow.
    (The letters are not the actual symbols of the elements).
                                                           Eø (volts)
    M2+(aq)+ 2e       →      M(s)                  -0.76
    N2+(aq) + 2e      →      N(s)                   -2.37
    P+(aq)    + e       →      P(s)                   +0.80
    Q2+(aq)   +2e      →      Q(s):                  -0.14
    1. The standard reduction potential for Fe 2+(aq) is -0.44 volts. Select the element which would best protect iron from rusting.(1 mark)
    2. Calculate the E ø value for the cell represented as M(s) / M2+(aq) // P+(aq) /P(s). (1mark)
  7. The formula given below represents a portion of a polymer
    CHEM28DIAG
    Give:
    1. The name of the polymer. (1mark)
    2. Draw the monomer. (1mark)
    3. One disadvantage of continued use of this polymer. (1mark)
  8. A sealed glass tube containing air at s.t.p was immersed in water at 1000c. Assuming that there was no increase in the volume of the glass tube due to the expansion of the glass, calculate the pressure of the inside tube. (standard pressure = 760mmHg,) ( 2marks).


MARKING SCHEME

  1. A thistle funnel does not have a tap while a dropping funnel has.√1// A dropping funnel delivers controlled amounts of liquid substances while a thistle funnel does not.  
  2.  
    1. A substance that dissociates in water to give hydrogen ions as the only positively charged ions..√1
    2. Sodium hydroxide solution causes a greater deflection on the ammeter than ammonia solution. .√1Sodium hydroxide completely ionizes.√ ½ to form sodium and hydroxide ions while ammonia solution partially ionizes.√ ½ to form ammonium and hydroxide ions.
  3.  
    1. fermentation.√1
    2. Ethanol forms hydrogen bonds .√ ½ with water while ethane does not//.√ ½ remains molecular/has only weak vanderwaals forces( intermolecular force)//.Ethane is non polar while ethanol is polar.
  4.  
    1. 234U → 230Th + 4He.√1
    2. Gamma rays will penetrate through the walls of the container and cause damage.
  5.  
    1. I..√1
      II More Oxygen is used to form CO2.√1
    2.  
      1. CH4 + 2O2 →CO2 + 2H2O
        IV       2V      1V      2V.√ ½
        80 cm3 150 cm3  75 cm3 150 cm3
        Volume of carbon (IV) oxide = 75 x 1 = 75cm3 .√ ½
      2. Volume of water = 2 x 75 = 150cm3
        Residual air = 5cm3 + 75cm3 + 150cm3.√ ½ = 230cm3 .√ ½
  6.  
    1. X. .√ ½ It is stable; it neither loses nor gains electrons.√ ½
    2. W and Y.√ 1
    3. YW.√ ½1
  7.  
    1. Thermometer should not be dipped in the mixture, .√ 1 it should be at the outlet point to the condenser.
      The direction of water flow is wrong/ condenser wrongly fixed.√ any 1
      No water bath is used
    2. Boiling point/ Freezing point/Density / refractive index
  8.  
    1. 2Pb(NO3)2(s)→2PbO+4NO2(g) +O2(g).√ 1
    2. Moles of NO2 gas=0.01208.√ ½
      moles of Pb(NO3)2=0.006.√ ½
      mass of Pb(NO3)2=0.006x331.√ ½ =1.986g.√ ½
  9.  
    1. Neutralization.√ 1
    2.  
      1. Calcium hydrogen carbonate.√ 1
      2. Drying agent. .√ 1 Extraction of sodium from Downs’s process..√ ½
  10. Kerosene floats on water therefore it continues to burn carbon (iv) oxide blanket covers the flame.√ 1// cuts off the supply of oxygen therefore burning stops .√ ½
  11.  
    1. ∆H1 – Bond breaking.√ ½ / activation Energy
      ∆ H3 – Energy evolved during reaction
    2. ∆H3 = ∆H1 + ∆ H2.√ 1
  12. Add excess zinc oxide.√ ½ to dilute HCl(aq).√ ½
    HNO3(aq) / H2SO4(aq).Filter. .√ ½
    To the filtrate add aqueous K2CO3(aq) / Na2CO3(aq) / (NH4)2 CO3(aq) to precipitate ZnCO3(S).√ ½
    Filter.√ ½ to obtain ZnCO3(S) as the residue. .√ ½
  13.  
    1. T = (32 x60) + 10 = 1930s .√ ½
      I = 0.5
      Q = It = 0.5 x 1930 = 765 C .√ ½
      0.44g deposited by 765C
      88g ?
      88/0.44 × 765 = 153000.√ ½
      Charge of X = 2
    2. X(OH)2.√ 1
  14. Butane.√ 1
    CHEM14ORG
  15.  
    1. Barium Sulphate (BaSO3).√ 1
    2. BaSO3(s) + 2HCI (aq) →BaCI2(aq) + SO2(aq).√ 1
    3. Changes from orange to green.√ 1
  16.  
    CHEM16ORG
    Empirical formula= C2H2O√ ½
    n = 3 √ ½
    Molecular formula = (C2H2O)3 = C6H6O3√ ½
  17.  
    1. Ammonia gas√ 1
    2. Filtration/precipitation/Crystallization√
    3. 2NaHCO3 (s)→ Na2CO3(s) + CO2 (g) + H2O (g)√ 1
  18. -Iron wool turns or rusts√ ½ due to formation of hydrated iron (III) oxide√ ½
    -Level of water inside the tube rises√ ½ to occupy the space left by oxygen√ ½
    -Level of water in the beaker will fall
  19.  
    1. The water contained impurities √ 1 (1mk) //presence of impurities elevate the Boiling point. // water contained dissolved ions//Hard.
    2.  
      1. Copper(II) sulphate;√ 1 at 400C ONLY 28gm is soluble leaving the rest undissolved. √ 1
        At 400C, all lead nitrate dissolves.
      2. 35-28=7g√ ½
  20. Equilibrium shift to the right (1mark)
    - Shift to the right √ ½
    - Shifts to the left ( equivalent to increase in pressure) (1mark)
  21.  
    1.  
      CHEM21RG
    2. 2H2(g) + O2(g) →2H2O(g)√ 1
  22. H2X (aq) + 2 NaOH (aq) → Na2X(aq) + H2 O(l)
    CHEM22AORG
  23.  
    1. NH4NO3(s) →N2O(g) + 2H2O(g)
    2. Over warm water.√ ½ Downward displacement of warm water because it is fairly soluble in cold water.√ ½
    3. Both red and blue litmus will not change colour√ 1
  24.  
    1. At room temperature √ 1cold and dilute sodium hydroxide
    2. Used in sterilizing of water / treatment of water / killing germs
      Used as a bleaching agent√ 1 any
      Antiseptic for mouth wash
      Fungicide
  25.  
    1. 2cr + -2 x 7 = -2 √ ½
      2cr - 14 = -2
      2cr = +12
      Cr = +6√ ½
    2. Oxidation - Fe2+√ 1 (Iron (II) ions) to Fe3+(increase of oxidation number/ loss of electron)
      Reduction – Chlorine to Cl-1( decrease in oxidation number/ gain of electron)√ 1
  26.  
    1. Bromine At room temp (25°c) Bromine is liquid since its M.P is -7°c and B.P 59°c/58.8°c.Room temp is between its M.P and B.P√ 1
    2. Atomic mass / molecular mass / molecule of iodine is higher than that of Cl
      Van der waals forces are stronger in I2 than Cl2 hence iodinesb.p is highest than that of Cl2
  27.  
    1. N         √1                                                                               
    2. Eø =0.80 +0.76√ ½
      = 1.56 volts     √ ½                                         
  28.  
    1. Polystyrene or polyphenylethene√ ½
    2.  
      CHEM28ORG√ 1
    3. non biodegradable√ 1
  29.  
    1. P1+ P2
      Volume is constant
      760 =   P2         P2 = 760 x 373√ 1 = 1038 mmHg√ 1
      273      373                  273
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