CHEMISTRY PAPER 2 Marking Scheme - 2019 KCSE Prediction Answers Set 1

Share via Whatsapp
  1.  
    1.  
      1.  
        1. X because its boiling point is lower than that of room temperature and it is slightly
          soluble in water
        2. V
      2. W
    2.  
      1. Alkaline earth metals
      2. G
      3. Covalent bond
        Because the bond is formed by sharing of electrons since they are both non-metals elements
      4. J2O3
      5. Tick
  2.  
    1.  
      1. E
        Rise in temperature is lower, showing that the acid is partially ionized hence some energy is used to ionize its molecules fully
        NaOH(aq) + CH3COOH(aq) → CH3COO.Na(aq) + H2O(l)
    2.  
      1. Is the amount of heat energy required to convert one mole of a liquid substance at its boiling point to its gaseous state.
      2. ...........
      3. ΔH1= -133 kJ/mole
        ΔH2= -188 kJ/mole
        ΔH3= -133 +188 = +55 kJ
      4. H2O(l) → H2O2 ΔH3= -133 +188 = +55 kJ
    3.  
      1. Is a substance that provide useful energy when it undergoes a chemical or nuclearreaction
      2.  
        1. Hydrogen gas burns to produce steam which is a non- pollutant to the environment
          Hydrogen gas has a high energy content hence very small amount produce a lot of heat energy
        2. Hydrogen gas can easily explode when burning since it is highly flammable unlike fossil fuels.
  3.  
    1. Solvay process
    2. Ammonia gas
      Limestone / calcium carbonate
      Brine / concentrated sodium chloride
    3. Ammonia gas
    4. Filtration
    5. Calcium chloride
      2NH4Cl(aq) + Ca(OH)2(aq) → CaCl2(aq) + 2H20(l) + 2NH3(g)
    6. Sodium carbonate
      2NaHClO3(s) → Na2C03(s) + H20(l) + C02(g)
      From equation : 2 moles NaHC03 produces 1 mole Na2C03
      R.M.M of NaHC03 is (1 x 23) + (1x1) + (1 x 12) + (3 x16) = 84
      (84g/1000g X 1) kg is 0.084 kg
      2 mole NaHC03 is 0.084 x0.168 kg
      R.M.M of Na3C03 is (2 x 23) + (1x12) + (3 x16) = 106
      (106g/100g x 1 kg) is 0.106 kg
      If, 0.168 kg NaHC03 produces 16 Kg
      98.128 produces (98.128 x 0.106 Z
  4.  
    1. -2.90 volts
    2. U
      Hydrogen is used as the reference electrode hence its E O is 0.00 volts
    3. Drawing
    4. On the diagram
    5. Eo cell = Eo reduced - Eo oxidized
      = (+0.34)- (-2.38) = +2.72 V
    6.  2 moles of e - deposits 63.5g Cu
      2 faradays deposits 63.5g
      2 x 96 500 I 1 = 193 000 c
      If, 63.5 g Cu is deposited by 193000 c
      1.48 g is deposited by 1.48 x 193 000 x 63.5 = 4498.2677 c
      Q = it
      4498.2677 = I x (2 x 60 x 60 ) + 30 x 60 I = 4498.2677/9000 = I = 0.4998A
  5.  
    1.  
      1. N/A
      2. CH3CH2CH20H
      3. Concentrated sulphuric (VI) acid
        Acidified potassium manganate (VII)
      4. Polypropene . used in manufacture of plastic crates, carpets, boxes
      5. Hydrogen gas
        2CH3CH1CH10H + 2K → CH3CH2CH2OK + H2(g)
        Potassium propoxide
    2. DRAWING
  6.  
    1. Magnetite
    2. This is because iron from the blast furnace is impure and presence of impurities lowers its melting point
    3. To produce calcium oxide which reacts with silica for form slag
    4. Slag is immiscible with molten iron
    5. To conserve heat energy in order to maintain the optimum temperature needed for the reduction of the iron (III) Oxide
    6. Carbon
      3C(s)+ 2Fe2O3(aq) → 3C4Fe(l) + 3C02(g)
    7.  Because the reaction between coke (or coal) and hot air at point A is highly exothermic.
    8. Pig iron
      H is reduced by blowing oxygen gas into molten iron which conve1is carbon into carbon (VI)oxide gas.
  7.   
    1.  
      1. Ca(HCO3)2(aq) + Ca(OH)2(aq)  → 2CaC03(s) + 2H20(l)
      2.  If, in 1000cm3 are 0.01 mole calcium hydroxide
        In 90cm3 are 90 x 0.01/1000 = 0.0009 mole of calcium hydrogen
      3. When soap solution is added, it initially will form scum because water will still be hard
        Later lather will be produced because all calcium ions in the water will have been precipitated
    2.  
      • The magnesium .and calcium ions in water are exchanged with sodium ions in the permutit
      • By passing a solution of concentration sodium chloride through the column
      • Leads to formation of boiler scales which acts as an insulating layer that leads to fuel wastage
    3. For forward reaction: H2O is the base since accepts a proton
    4. For backward reaction: HO2 is the base since it accepts a proton.
Join our whatsapp group for latest updates

Download CHEMISTRY PAPER 2 Marking Scheme - 2019 KCSE Prediction Answers Set 1.


Tap Here to Download for 50/-




Why download?

  • ✔ To read offline at any time.
  • ✔ To Print at your convenience
  • ✔ Share Easily with Friends / Students


Get on WhatsApp Download as PDF
.
Subscribe now

access all the content at an affordable rate
or
Buy any individual paper or notes as a pdf via MPESA
and get it sent to you via WhatsApp

 

What does our community say about us?

Join our community on:

  • easyelimu app
  • Telegram
  • facebook page
  • twitter page
  • Pinterest