Question

Two statements are given below.
Statement I: Adsorption of a gas on the surface of charcoal is primarily an exothermic process.

Statement II: A closed vessel containing \( O_2(g) \), \( H_2(g) \), \( Cl_2(g) \), \( NH_3(g) \) has a pressure of 9 atm. About 1 g of charcoal was added to this vessel and after some time its pressure is \( P' \) atm. It is observed that \( P'>P \). Choose the correct answer.

• A. Both statements I and II are correct
• B. Both statements I and II are not correct
• C. Statement I is correct but statement II is not correct
• D. Statement I is not correct but statement II is correct

Hint:

In adsorption, the process is generally exothermic, and it causes a decrease in pressure due to the transition of gas molecules to the surface.

Answer 1

The Correct Option is C

Step 1:
Statement I is correct. Adsorption of gases on a surface is indeed an exothermic process, as the gas molecules lose energy while being adsorbed onto the surface.
Step 2:
Statement II is incorrect. When a gas is adsorbed on charcoal, it leads to a decrease in pressure, not an increase. This happens because the molecules move from the gas phase to the surface, reducing the volume of the gas phase and therefore lowering the pressure in the vessel. Hence, the pressure \( P' \) should be less than \( P \), not greater. Thus, the correct answer is option (3).