Neco 2018 Chemistry Question 49

Practice objective / multiple choice question 49 from the 2018 Neco Chemistry examination.

Neco 2018 Chemistry Objective / Multiple Choice Hard Difficulty
Question 49 NECO • 2018 • CHEMISTRY • objective

A wastewater stream contains phenol at an initial concentration of 50 mg L⁻¹. The stream first undergoes a rapid treatment that instantaneously removes 40 % of the phenol. The remaining phenol then degrades biologically following first‑order kinetics with a rate constant \(k = 0.15\) day⁻¹ at 25 °C. (i) Calculate the phenol concentration after 5 days of treatment. (ii) Determine the time required for the phenol concentration to fall below 1 mg L⁻¹ after the start of treatment.

Answer Options

A. (i) 15.6 mg L⁻¹ after 5 days; (ii) ≈25.1 days to reach <1 mg L⁻¹.
B. (i) 13.4 mg L⁻¹ after 5 days; (ii) ≈21.9 days to reach <1 mg L⁻¹.
C. (i) 12.8 mg L⁻¹ after 5 days; (ii) ≈20.3 days to reach <1 mg L⁻¹.
Correct Answer D. (i) 14.2 mg L⁻¹ after 5 days; (ii) ≈22.7 days to reach <1 mg L⁻¹.
Correct Answer
D
Correct Option:
(i) 14.2 mg L⁻¹ after 5 days; (ii) ≈22.7 days to reach <1 mg L⁻¹.

About This Question

This is Neco 2018 Chemistry Question 49. It is one of the objective questions from the 2018 Neco Chemistry examination.

Difficulty level: Hard .

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