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

Difficulty level: Hard .

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