Q19 / 150 · MHT CET 2026 (19 April Shift 2) · Chemistry
Which of the following hydrocarbons has stronger London dispersion forces ?
- AMethane
- BEthane
- Correct answerCn-pentane
- Dneo-pentane
Solution
London dispersion forces increase with an increase in molecular mass and the surface area of the molecule.
Methane ($CH_4$) and ethane ($C_2H_6$) have lower molecular masses compared to n-pentane and neo-pentane ($C_5H_{12}$), resulting in weaker dispersion forces.
Between n-pentane and neo-pentane, n-pentane is a straight-chain alkane, whereas neo-pentane is highly branched and nearly spherical.
The straight-chain structure of n-pentane provides a larger surface area for intermolecular contact compared to the compact structure of neo-pentane.
Therefore, n-pentane has the strongest London dispersion forces among the given hydrocarbons.
Answer: n-pentane
Methane ($CH_4$) and ethane ($C_2H_6$) have lower molecular masses compared to n-pentane and neo-pentane ($C_5H_{12}$), resulting in weaker dispersion forces.
Between n-pentane and neo-pentane, n-pentane is a straight-chain alkane, whereas neo-pentane is highly branched and nearly spherical.
The straight-chain structure of n-pentane provides a larger surface area for intermolecular contact compared to the compact structure of neo-pentane.
Therefore, n-pentane has the strongest London dispersion forces among the given hydrocarbons.
Answer: n-pentane
Hence, the correct answer is option: 'C'.