What is the difference in molar mass of Undecane and Dodecane?

Alkanes follow the general formula $C_nH_{2n+2}$.
For undecane ($n=11$): $C_{11}H_{24}$
For dodecane ($n=12$): $C_{12}H_{26}$

Using atomic masses $C \approx 12.01 \text{ g/mol}$ and $H \approx 1.008 \text{ g/mol}$:
Undecane molar mass: $11 \times 12.01 + 24 \times 1.008 = 156.302 \text{ g/mol}$
Dodecane molar mass: $12 \times 12.01 + 26 \times 1.008 = 170.328 \text{ g/mol}$

The difference is $170.328 - 156.302 = 14.026 \text{ g/mol}$, which rounds to $14 \text{ g/mol}$.

Equivalently, consecutive alkanes differ by a $CH_2$ group with molar mass $12.01 + 2 \times 1.008 = 14.026 \text{ g/mol}$.

Correct option: D $14 \text{ g/mol}$