Waec Model Questions Vol1 2025 Chemistry Question 5

Practice objective / multiple choice question 5 from the 2025 Waec Model Questions Vol1 Chemistry examination.

Waec Model Questions Vol1 2025 Chemistry Objective / Multiple Choice Hard Difficulty
Question 5 WAEC_MODEL_QUESTIONS_VOL1 • 2025 • CHEMISTRY • objective

An alloy pipe (brass) contains 70 % Cu and 30 % Zn by mass and has a total mass of 2.00 kg. The pipe is a solid cylinder 1.20 m long with an outer diameter of 5.0 cm. When immersed in 0.10 M HCl, only the zinc component corrodes according to Zn + 2H⁺ → Zn²⁺ + H₂. The corrosion proceeds at a current density of 0.00025 A cm⁻² over the entire external surface. Assuming 100 % current efficiency, calculate (a) the mass of zinc lost after 10 days and (b) the percentage loss of the total pipe mass. (F = 96485 C mol⁻¹, atomic weight Zn = 65.38 g mol⁻¹)

Answer Options

A. a) 130 g of Zn lost; b) 6.5 % of total mass
Correct Answer B. a) 138 g of Zn lost; b) 6.9 % of total mass
C. a) 115 g of Zn lost; b) 5.8 % of total mass
D. a) 145 g of Zn lost; b) 7.2 % of total mass
Correct Answer
B
Correct Option:
a) 138 g of Zn lost; b) 6.9 % of total mass

About This Question

This is Waec Model Questions Vol1 2025 Chemistry Question 5. It is one of the objective questions from the 2025 Waec Model Questions Vol1 Chemistry examination.

Difficulty level: Hard .

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