JAMB Chemistry 2020 Objective — Question 9

Question 9 of 40 from the Joint Admissions and Matriculation Board (JAMB) Chemistry 2020 Objective paper, with the correct answer and a full explanation.

9. A hydrated salt of formula FeSO4.xH2O contains 45.3% of water of crystallization. Calculate the value of x [Fe=56,S=32,O=16,H=1]

A. A. 7Correct
B. B. 6
C. C. 5
D. D. 4

Explanation

Molar mass of FeSO4 = 152. Let x = number of water molecules: (18x)/(152+18x) = 0.453. Solving gives x ≈ 7, so the formula is FeSO4.7H2O (green vitriol).

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