JAMB Chemistry 2008 Objective — Question 25

Question 25 of 50 from the Joint Admissions and Matriculation Board (JAMB) Chemistry 2008 Objective paper, with the correct answer and a full explanation.

If a given quantity of electricity liberates 0.65 g of Zn2+, what amount of Hg2+ would be liberated by the same quantity of current?

A. 1.00g
B. 2.01gCorrect
C. 4.02g
D. 8.04g

Explanation

From Faraday's second law: n1c1=n2c2. Here, let us write: nZn cZn = nHg cHg. Mole of Zn = (0.65/65)mol=0.01mol. cZn=+2, cHg=+2. 0.01mol x nZn x 2; nHg=0.01mol. Mass of Hg = mole of Hg x Molar mass = (0.01mol x 201g) = 2.01g.

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