Question

the empirical formula of a compound of boron and hydrogen is bh₃. its molar mass is 27.7g/mol. determine the molecular formula of the compound.
bh₃
bh₆
b₂h₆
b₂h₃

Explanation:

Step1: Calculate empirical formula mass

The atomic mass of B (boron) is approximately 10.81 g/mol and H (hydrogen) is approximately 1.01 g/mol. For the empirical formula $BH_3$, the empirical - formula mass $M_{empirical}=(1\times10.81)+(3\times1.01)=10.81 + 3.03=13.84$ g/mol.

Step2: Find the ratio n

The ratio $n=\frac{M_{molecular}}{M_{empirical}}$, where $M_{molecular} = 27.7$ g/mol and $M_{empirical}=13.84$ g/mol. So, $n=\frac{27.7}{13.84}\approx2$.

Step3: Determine the molecular formula

The molecular formula is $(BH_3)_n$. Since $n = 2$, the molecular formula is $B_2H_6$.

Answer:

C. $B_2H_6$