Question

Two statements are given below
Statement I: Adsorption of a gas on the surface of charcoal is primarily an exothermic reaction
Statement II: A closed vessel contains O$_2$, H$_2$, Cl$_2$, NH$_3$ gases. Its pressure is P (atm). About 1 g of charcoal is added to this vessel and after some time its pressure was found to be less than P (atm)
The correct answer is

• A. Both Statements - I and Statement - II are correct
• B. Both Statements - I and Statement - 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:

Remember that adsorption is generally exothermic. Also, adsorbents like charcoal can reduce the pressure of a gas mixture by adsorbing some of the gases.

Answer 1

The Correct Option is A

Statement I: Adsorption of a gas on the surface of charcoal is primarily an exothermic reaction. This statement is correct. Adsorption is generally an exothermic process because the adsorbate molecules lose kinetic energy upon adsorption onto the adsorbent surface. 

Statement II: A closed vessel contains O$_2$, H$_2$, Cl$_2$, NH$_3$ gases. Its pressure is P (atm). About 1 g of charcoal is added to this vessel and after some time its pressure was found to be less than P (atm). This statement is also correct. Charcoal is a good adsorbent. When charcoal is added, it adsorbs some of the gases present in the vessel. This reduces the number of gas molecules in the vessel, leading to a decrease in pressure. 

Since both statements are correct, the correct answer is option (1).