Neco Model Questions Vol1 2025 Chemistry Question 14

Practice objective / multiple choice question 14 from the 2025 Neco Model Questions Vol1 Chemistry examination.

Neco Model Questions Vol1 2025 Chemistry Objective / Multiple Choice Hard Difficulty
Question 14 NECO_MODEL_QUESTIONS_VOL1 • 2025 • CHEMISTRY • objective

A lake contains dissolved calcium at a concentration of 2.5 mg L⁻¹ as Ca²⁺ and bicarbonate at 150 mg L⁻¹ as HCO₃⁻. The water pH is 8.5. Using the second dissociation constant of carbonic acid K₂ = 4.7×10⁻¹¹ and the solubility product of calcite Ksp = 4.8×10⁻⁹ at 25 °C, calculate the saturation index (SI) for calcite and state whether the water is undersaturated, saturated or supersaturated with respect to calcite.

Answer Options

A. SI ≈ -0.32; the water is supersaturated with respect to calcite.
B. SI ≈ -0.10; the water is undersaturated with respect to calcite.
Correct Answer C. SI ≈ -0.32; the water is undersaturated with respect to calcite.
D. SI ≈ 0.15; the water is supersaturated with respect to calcite.
Correct Answer
C
Correct Option:
SI ≈ -0.32; the water is undersaturated with respect to calcite.

About This Question

This is Neco Model Questions Vol1 2025 Chemistry Question 14. It is one of the objective questions from the 2025 Neco Model Questions Vol1 Chemistry examination.

Difficulty level: Hard .

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