NEET Chemistry: Thermodynamic Equilibrium questions with solutions

Q1. When a volatile liquid is introduced into an evacuated closed vessel at a particular temperature, both evaporation and condensation take place simultaneously. The system reaches equilibrium state when:

1. the liquid is completely transformed into the corresponding vapour
2. equal amounts of liquid and vapour are present in the
3. the rate of evaporation becomes equal to the rate of condensation
4. liquid cannot be converted into vapour and vice versa

Answer: the rate of evaporation becomes equal to the rate of condensation

In a closed vessel, vapor molecules keep returning to the liquid while liquid molecules keep escaping into vapor. Equilibrium is reached when these two opposing rates become equal, so the amounts of liquid and vapor stay constant overall.