The percent composition of hydrogen is 18.3%.
What is percent composition?
The term percent composition refers to the percentage of a particular component in a compound. It is contained as the ratio of the mass of that component to the total mass multiplied by 100.
From the law of conservation of mass, total mass of beryllium hydride(BeH2) = 85.2 g
Mass of hydrogen = 15.6 g
Percent composition of hydrogen = 15.6 g/ 85.2 g × 100/1 = 18.3%
