Post-UTME Chemistry 2016 Objective — Question 6
Question 6 of 20 from the Post-UTME Screening (Post-UTME) Chemistry 2016 Objective paper, with the correct answer and a full explanation.
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Cu2+(aq) [pale blue] + 4NH3(aq) <=> [Cu(NH3)4]2+(aq) [Deep blue solution]. In the equation above, addition of a few drops of dilute hydrochloric acid will produce
- A. an increase in the deepness of the solution
- B. a stable chemical system
- C. a decrease in the deepness of the solutionCorrect
- D. a decrease in the concentration of Cu2+
Explanation
HCl reacts with (protonates) free NH3, reducing its concentration and shifting equilibrium back towards pale blue Cu2+, decreasing the deep blue colour.
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