Question

The number of $C$ atoms in $2-$methyl branched alkane having a molecular mass of $254$ are:

(Enter answer in terms of number of carbons$/3$)

Answer 1

Since it is an alkane, it's molecular formula is $C_n{H}_{2n+2}$.
Molecular weight $=12n+2n+2=254$
$⟹14n=252$
$⟹n=18$
The compound is a 18 carbon alkane.

So the answer is $\frac{18}{3}=6$.