Question

The general chemical formula of alkanes is:

• A. $C_n{H}_{4n}$
• B. $C_n{H}_{2n+2}$
• C. $C_n{H}_{2n}$
• D. $C_n{H}_{2n-2}$

Answer 1

The correct option is B $C_n{H}_{2n+2}$

The general formula of a non-cyclic alkane is $C_n{H}_{2n+2}$. In unbranched carbon chain, each carbon in the middle of the chain is connected to 2 carbon atoms and 2 hydrogen atoms. The terminal carbon atoms are connected to 3 hydrogen atoms each.
In case of a branched alkane, one of the hydrogens on a carbon is replaced by carbon, but that increases one more terminal carbon which connects to 3 hydrogens. So the general form $C_n{H}_{2n+2}$ remains the same (except for cycloalkanes).