WAEC Chemistry 2013 Objective — Question 36

Question 36 of 50 from the West African Examinations Council (WAEC) Chemistry 2013 Objective paper, with the correct answer and a full explanation.

Which of the following substances are electrolytes? I. PbBr2(l) II. NaCl(aq) III. NaCl(s) IV. C6H12O6(aq)

A. I and II onlyCorrect
B. I, II and IV only
C. III and IV only
D. I and III only

Explanation

Electrolytes must be composed of ions, rather than molecules. Thus, C6H12O6 is not an electrolyte. Also, for any substance (which is already composed of ions) to serve as an electrolyte, it must be in either molten or aqueous form. Thus, NaCl(s) which is solid sodium chloride, is not an electrolyte. PbBr2(l) means molten form of lead(II) bromide, NaCl(aq) means aqueous form of sodium chloride. Both of them are fully functioning electrolytes.

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