WAEC 2022 CHEMISTRY PRACTICAL QUESTIONS AND ANSWERS
WAEC 2022 CHEMISTRY PRACTICAL ANSWERS-EXAMOXYGEN.COM
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Tuesday, 14th June, 2022
Chemistry 3 (Practical) (Alternative A)
09:30am – 11:30am (1st Set)
Chemistry 3 (Practical) (Alternative A)
12:00noon – 2:00pm (2nd Set)
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Chemistry-Practical-Answers-Examoxygen.com
(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
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(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⁻
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(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
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