One of the hydrides of boron has molar mass=122.22g/mol and is 11.55% by mass hydrogen. Determine its molecular formula?

1 Answer
Mar 9, 2018



Atomic weight of boron is 10.8 and of hydrogen is 1.
Percentage of mass of boron is 88.45% and of hydrogen 11.55%. Dividing the percentages by the respective atomic masses, we obtain a ratio of boron to hydrogen of 1: 1.4, in integer numbers 5:7. The minimal formula is therefore #B_5H_7#, which has a molecular mass of 61. Since the molar mass of the compound is 122, the mole cular formula is #B_10H_14#