Question

What is the molecular formula for a compound that has an empirical formula of $C_3{H}_7$ and a molar mass of $86.2g/mol$?

• A. $C_9{H}_{21}$
• B. $C_6{H}_{14}$
• C. $C_3{H}_7$
• D. None of the above

Answer 1

The correct option is B $C_6{H}_{14}$

Let the molecular formula of the compound be $(C_3{H}_7{)}_n$

Given, Molar mass of compound $=86.2$

Molar mass of $(C_3{H}_7{)}_n=n(3\times 12+7)=n(43)$

$\Rightarrow n\left(43\right)=86.2$

$\Rightarrow n\approx 2$

So, Molecular formula is $(C_3{H}_7{)}_2$ i.e. $C_6{H}_{1}4$