Class 12th

This is a Multiple Choice Type Questions as classified in NCERT Exemplar

Ans: Correct option is (ii)

As the process of adsorption is an exothermic one; physical adsorption occurs readily at low temperature and decreases with an increase in the temperature as equilibrium shifts in the backward direction. This is known as Le-Chatelier's principle, hence the correct option is (ii).

This is a Multiple Choice Type Questions as classified in NCERT Exemplar

Ans: Correct option is (iii)

When both adsorption and absorption occur simultaneously it is known as sorption; hence the correct option is (iii).

This is a Multiple Choice Type Questions as classified in NCERT Exemplar

Ans: Correct option is (iv) 

As gas-gas forms up a homogeneous composition, so the correct option is (iv).

This is a Multiple Choice Type Questions as classified in NCERT Exemplar

Ans: Correct option is (iv)

In equilibrium ΔG=0 so ΔG=ΔH-TΔS which means ΔH=TΔS therefore the correct option is (ii).

This is a Multiple Choice Type Questions as classified in NCERT Exemplar

Ans: Correct option is (iii)

In homogeneous catalysis, the reactant as well as the product both are in same phase and composition is uniform throughout hence the correct option is (iii).

This is a Short Answers Type Questions as classified in NCERT Exemplar

Ans: The rate of an enzyme reaction is maximum at a definite temperature, called the optimum temperature. On either side of the optimum temperature, the enzyme activity decreases. The optimum temperature range for enzymatic activity is 298-310 K. Human body temperature being 310 K is suited for enzyme-catalysed reactions. Therefore, during fever, catalytic activity of the enzyme may get affected.

This is a Short Answers Type Questions as classified in NCERT Exemplar

Ans: When gaseous molecules come in contact with the surface of a solid catalyst, a weak chemical combination takes place between the surface of the catalyst and the gaseous molecules, which increases the concentration of reactants on the surface. Different molecules adsorbed side by side have better chance to react and form new molecules. This enhances the rate of reaction. Also, adsorption is an exothermic process. The heat released in the process of adsorption is utilised in enhancing the reaction rate.

This is a Short Answers Type Questions as classified in NCERT Exemplar

Ans: The gaseous molecules diffuse on to the surface of the solid catalyst and get adsorbed. After the required chemical changes the products diffuse away from the surface of the catalyst leaving the surface free for more reactant molecules to get adsorbed and undergo reaction.

This is a Short Answers Type Questions as classified in NCERT Exemplar

Ans: After the reaction is over between adsorbed reactants, the process of desorption is important to remove products and further create space for the other reactant molecules to approach the surface and react.

This is a Short Answers Type Questions as classified in NCERT Exemplar

Ans: The process of physisorption for example that of H2 on finely divided nickel, involves weak van there Waals' forces. With increase in temperature, hydrogen molecules dissociate into hydrogen atoms which are held on the surface by chemisorption.