Answer
Molecular formula is $B_{2}H_{6}$ .
Work Step by Step
Strategy: 1- Find the empirical formula mass.
2- by dividing molecular mass with empirical formula mass, we can find the number that empirical formula mass must be multiplied to find the molecular formula.
The empirical formula mass for $BH_{3}$ :
1x11.0 + 3x1.0 = 14.0 amu
We are given the molecular mass of compound 28 amu, so we can find the number empirical formula mass must be multiplied to find the molecular mass:
n = $\frac{Molecular mass}{empirical (formula-mass)}$
n = $\frac{28}{14}$ = 2
So molecular formula should be $(BH_{3})_2$
Therefore molecular formula is $B_{2}H_{6}$ .
