Question

Which of the following is not a case of physical equilibrium?

• A. Formation of ${\mathrm{NH}}_4\mathrm{OH}$
• B. Conversion of water into vapor
• C. Conversion of water vapor onto liquid water
• D. None of these

Answer 1

The correct option is A

Formation of ${\mathrm{NH}}_4\mathrm{OH}$

Explanation for correct option:

A. Formation of ${\mathrm{NH}}_4\mathrm{OH}$

Physical equilibrium:

• A physical change occurs when there is a change in phase from one substance to another.
• The equilibrium that is attained in physical processes is known as physical equilibrium.
• In this type of equilibrium, there is no chemical reaction involved.
• An example of physical equilibrium is the conversion of water into vapor.

Formation of ${\mathrm{NH}}_4\mathrm{OH}$ is not a case of physical equilibrium as it involves a chemical change.

Explanation for incorrect options:

B. Conversion of water into vapor is a physical equilibrium as there is a change in physical state from liquid to a gaseous state.

C. Conversion of water vapor onto liquid water is a physical equilibrium as there is a change in phase from gaseous to a liquid phase.

Hence, the correct option is A i.e. Formation of ${\mathrm{NH}}_4\mathrm{OH}$.