What is the percentage by mass of oxygen in Al2(SO4)3. 2H2O? [Al = 27, S = 32, H = 1, O = 16]

A. 14.29%
B. 25.39%
C. 50.79%
D. 59.25%

Correct Answer:

Option D – 59.25%

Explanation

Al2(SO4)3. 2H2O

2 * 27 + 3*32 + 14 * 16 + 4 * 1 =
54 + 96 + 224 + 4 = 378
% O2 = (224/378) * (100/1) = 59.25%