Water contains 80 mg L⁻¹ nitrate (NO₃⁻). Two treatment options are considered.

Option A: First‑order decay with rate constant $k_{A}=0.15$ min⁻¹.

Option B: An adsorption step that instantly removes 60 % of nitrate, after which the remaining concentration decays by first‑order kinetics with $k_{B}=0.05$ min⁻¹.

For each option, calculate the time required to reduce the nitrate concentration to 10 mg L⁻¹. Which option achieves the target faster?

Question

Water contains 80 mg L⁻¹ nitrate (NO₃⁻). Two treatment options are considered.

Option A: First‑order decay with rate constant $k_{A}=0.15$ min⁻¹.

Option B: An adsorption step that instantly removes 60 % of nitrate, after which the remaining concentration decays by first‑order kinetics with $k_{B}=0.05$ min⁻¹.

For each option, calculate the time required to reduce the nitrate concentration to 10 mg L⁻¹. Which option achieves the target faster?

Accepted Answer

Option A: 13.9 min; Option B: 23.3 min; Option A is faster.

Igcse Model Questions Vol1 2020 Chemistry Question 32

Answer Options

About This Question

Master the Exam!