NEETChemistrySolutions
A mixture of ethanol and acetone shows a positive deviation from Raoult's law. Which of the following best explains this behaviour at the molecular level?
Options
- AFormation of new intermolecular hydrogen bonds between ethanol and acetone molecules.
- BAcetone molecules get between ethanol molecules and break some of the existing hydrogen bonds.
- CThe escaping tendency of the molecules from the liquid phase decreases upon mixing.
- DAn increase in the strength of dipole-dipole interactions between the two components.
Correct answer
B. Acetone molecules get between ethanol molecules and break some of the existing hydrogen bonds.
Step-by-step solution
In pure ethanol, the molecules are strongly held together by intermolecular hydrogen bonding. When acetone is added to ethanol, the acetone molecules get between the ethanol molecules and break some of these hydrogen bonds. Due to the weakening of the attractive forces, the interactions between the unlike molecules (ethanol and acetone) become weaker than those between the like molecules (ethanol-ethanol). This increases the escaping tendency of the molecules from the liquid phase, resulting in a higher vapour pres