Neco 2017 Chemistry Question 47

Practice objective / multiple choice question 47 from the 2017 Neco Chemistry examination.

Neco 2017 Chemistry Objective / Multiple Choice Hard Difficulty
Question 47 NECO • 2017 • CHEMISTRY • objective

A wastewater sample contains 0.500 mg L⁻¹ of pollutant X. A treatment step removes 30 % of X. The treated effluent is then mixed with river water in a 1:3 volume ratio (treated:river). The resulting mixture is stored for 5 days, during which X degrades by first‑order kinetics with half‑life 2 days. (i) Calculate the concentration of X after the three operations. (ii) The permissible limit for X in surface water is 0.010 mg L⁻¹. Does the final concentration satisfy the limit? (iii) If it does not, determine the minimum overall percentage removal that the initial treatment must achieve (keeping the same dilution and degradation conditions) to meet the limit.

Answer Options

A. Final concentration ≈0.008 mg L⁻¹; meets limit; at least 40 % total removal (≈10 % more than the present 30 %) is required
B. Final concentration ≈0.020 mg L⁻¹; does not meet limit; at least 60 % total removal (≈30 % more than the present 30 %) is required
Correct Answer C. Final concentration ≈0.016 mg L⁻¹; does not meet limit; at least 55 % total removal (≈25 % more than the present 30 %) is required
D. Final concentration ≈0.012 mg L⁻¹; does not meet limit; at least 48 % total removal (≈18 % more than the present 30 %) is required
Correct Answer
C
Correct Option:
Final concentration ≈0.016 mg L⁻¹; does not meet limit; at least 55 % total removal (≈25 % more than the present 30 %) is required

About This Question

This is Neco 2017 Chemistry Question 47. It is one of the objective questions from the 2017 Neco Chemistry examination.

Difficulty level: Hard .

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