What is the percentage composition of oxygen in water (H2O)?
A
66.7%
B
11.1%
C
88.9%
D
50%
Correct Answer: Option C — 88.9%
Explanation:
Water's molar mass is 18 g/mol, of which oxygen contributes 16 g. Dividing 16 by 18 and multiplying by 100 gives approximately 88.9 percent oxygen by mass in water.