WAEC Chemistry Practical Alternative B Theoretical value for VE

[Serifat Obayemi]

Theoretical value for VE For 2026 WAEC Chemistry Practical Alternative B

From the instruction paper:
(i)D = H₂C₂O₄.2H₂O
(ii)E = KMnO₄
(iii)Mass concentration of H₂C₂O₄.2H₂O = 6.30 g/dm³
(iv)Mass concentration of KMnO₄ = 3.10 g/dm³
(v)VD = 25 cm³

*My workings*
Molar mass of H₂C₂O₄.2H₂O = 126 g/mol
Molar mass of KMnO₄ = 158 g/mol
Equation:
5C₂O₄²⁻ + 2MnO₄⁻ + 16H⁺ ----> 2Mn²⁺ + 8H₂O + 10CO₂
nD = 5 and nE = 2

Step 1: Molar concentration of H₂C₂O₄.2H₂O
Formula to use is
CD = mass concentration/molar mass
CD = 6.30/126
CD = 0.05 mol/dm³

Step 2: Molar concentration of KMnO₄
Formula to use is
CE = Mass concentration/molar mass
CE = 3.10/158
CE = 0.0196 mol/dm³

Step 3: VE
Formula to use is
VE = CDVDnE/CEnD
VE = (0.05 × 25 × 2)/(0.0196 × 5)
VE = 25.50 cm³

 

[Serifat Obayemi]

For any teacher doing alternative B