Waec May/June 2022 Chemistry Practical Answers

Waec May/June 2022 Chemistry Practical Answers
  • ======================
    ""CHEMISTRY PRACTICAL EXAM""
    =====================



    *TAKE NOTE*


    For question 1

    Use your school's endpoint and use it wherever you see 24.10cm³....and calculator with it

    Use the answer in 1b(i) to solve in 1b(Ii)





    (1a)
    Volume of pipette used, VA = 25.0cm³

    [TABULATE]

    Burette Reading | Rough titre | 1st titre | 2nd titre |

    Final Burette reading (cm³) | 25.60 | 32.80 | 26.40

    Initial Burette reading (cm³) | 1.20 | 8.70 | 2.30

    Volume of Na₂S₂O₃ used | 24.40 | 24.10 | 24.10

    Average burette reading = (24.10 + 24.10)/2
    Average volume of Na₂S₂O₃ used = 24.10cm³
    VB = 24.10cm³

    (1bi)
    Given: CB = 0.1mol/dm³
    VB = 24.10cm³
    VA = 25.0cm³
    CA =?
    From equation nA/nB = 1/2
    .: Using (CABA)/CBVB = (nA)/nB

    (CA x 25)/(0.1x24.10) = 1/2
    CA = (0.1x24.10)/(25x2)
    CA = 0.0482mol/dm³
    .: Concentration of iodine in A = 0.0482mol/dm³

    (1bii)
    Mass in gramms of iodine in 1dm³ of A = Molarity × Molar mass of iodine
    = 0.0482×127(2)
    = 12.2428g/dm³
    =============================

    (2a)
    [TABULATE]

    =TEST=
    C + Distilled water

    =OBSERVATION=
    It dissolves completely to give a light green solution.

    =INFERENCE=
    Soluble salt.

    (2ai)
    =TEST=
    Solution C + NaOH in drops and in excess + Heat gently

    =OBSERVATION=
    A dirty green precipitate is formed which remains insoluble in excess.
    Effervescence occurs in which a colourless gas with a pungent smell which turns red litmus blue is given off.

    =INFERENCE=
    Fe²⁺ is present.
    NH₃ gas form.
    NH₄⁺ is present.

    (2aii)
    =TEST=
    Solution + BaCl₂ + dilute HCL in excess

    =OBSERVATION=
    A white precipitate is formed.
    The white precipitate remains insoluble and gives a white dense forms

    =INFERENCE=
    SO₄²⁻, CO₃²⁻, SO₃²⁻, is present.
    SO₄²⁻ confirmed.

    (2b)
    Cations → Fe²⁺ and NH₄⁺
    Anions → SO₄²⁻
    =============================

    (3a)
    Carbon (iv) oxide turns like water milky white while sulphur (iv) oxide does not

    (3b)
    (I) H₂: Downward displacement of air
    (II) NH₃: Downward displacement of air
    (III) HCL: Upward displacement of air

    (3bii)
    I - It is less dense than air
    II - It is less dense than air
    III - It is denser than air

    (3c)
    (i) Distillation
    (ii) Filtration followed by evaporation to dryness

    (3d)
    This is because KCl react with NaHCO₃ to form two salts
    =============================



    NUMBER 1






    COMPLETE NUMBER 2


    NUMBER 3







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