WAEC GCE Chemistry Practical 2026 Expo Questions and Answers

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Volume of Pipette = 25.0 cm³

Burette Readings (cm³)	1st Time	2nd Time	3rd Time
Final Readings	13.00	13.10	13.20
Initial Readings	0.00	0.00	0.00
Volume of Acid Used	13.00	13.10	13.20

 

1a. Average Volume of A Used, V_A

V_A =
(13.00 + 13.10 + 13.20) / 3

= 13.10 cm³

1b. Concentration of KOH
_CB = ? mol dm^-3

V_B = 25.0 cm³

Equation:
CH₃COOH + KOH → CH₃COOK + H₂O

nA = 1
nB = 1

Continuation of 1(bi)

Using the formula:

C_BV_{B            nA}

———— = ——
C_AV_{A.           nB}

C_B =
(C_A × V_A × n_B) /
(V_B × n_A)

C_B =
(0.1 × 13.1 × 1) /
(25 × 1)

C_B =
13.1 / 250

C_B = 0.0524 mol dm^-3

 

1(bii) Concentration of B in g/dm³

Mass Concentration = Molar Concentration × Molar Mass

Molar Mass of KOH:

K = 39
O = 16
H = 1

Molar Mass = 39 + 16 + 1

= 56 g/mol

Mass Concentration of KOH in B:

= 0.0524 × 56

= 2.93 g/dm³

Continuation of 1(biv)

Amount (Moles) of Ethanoic Acid

Using the formula:

n = CV

n =
(0.1 × 13.1) / 1000

n = 0.00131 mol

 

From the equation:

CH₃COOH + KOH → CH₃COOK + H₂O

1 mole of CH₃COOH produces 1 mole of H₂O

Therefore:

0.00131 mol of CH₃COOH produces
0.00131 mol of H₂O

 

Using:

Number of molecules = Number of moles × Avogadro’s constant

Number of H₂O molecules =
0.00131 × 6.02 × 10²³

= 7.8 × 10²⁰ molecules

QUESTION 2
TEST	OBSERVATION	INFERENCE
(a) Sample C + few cm³ of dilute acid + filter	Effervescence occurs with the release of a colourless, odourless gas which turns lime water milky. A clear or colourless filtrate and a white residue were obtained.	The gas is CO₂. CO₃²⁻ ion present. The solution is a mixture of a soluble and insoluble substance.
(b)(i) First portion + NaOH in drops, then in excess	White (chalky) precipitate is formed. Precipitate dissolves to give a clear or colourless solution.	Pb²⁺ or Ca²⁺ ions present. Pb²⁺ ions present.
(b)(ii) Another portion + NH₃ in drops, then in excess	White chalky precipitate is formed. Precipitate remains insoluble in excess.	Pb²⁺ ion present.
(c) Residue + 2 cm³ of distilled H₂O	—	—

(3a)

Complete the table

 

Under; Apparatus

(i) Measuring cylinder (or Pipette / Burette)

(ii) Clay triangle

(iii) Crucible

(iv) Bomb calorimeter

 

Under; Use

(i)For measuring specific volume of a liquid

(ii)To support a crucible being heated by a Bunsen burner

(iii)As container for melting and heating to a very high temperature

(iv)To measure the heat of combustion of a particular reaction

 

(3b)

(i)PbSO⁴ (Insoluble)

(ii)PbCl² (slightly soluble in cold water, soluble in hot water

(iii)Pb(NO³)² (soluble)

 

Order; PbSO⁴ <PbCl² <Pb (NO³)²

 

(3c)

(i)KNO³(aq); No effect. It is a neutral salt formed from strong acid (HNO³) and a strong base (KOH)

(ii)K²CO³; turns red litmus blue. It is a basic salt formed from a weak acid (H²CO³) and strong base (KOH)

(iii)Al²(SO⁴)³(aq); turns blue litmus red. It is an acidic salt; aluminium ions undergo hydrolysis in water to produce H+ ions