Ncert Exercises & Solutions

Select the correct option based on statements below:

Assertion (A):	Spontaneous process is an irreversible process and may be reversed by some external agency.
Reason (R):	A decrease in enthalpy is a contributing factor to spontaneity.

1.	Both (A) and (R) are true and (R) is the correct explanation of (A).
2.	Both (A) and (R) are true but (R) is not the correct explanation of (A).
3.	(A) is true but (R) is false.
4.	(A) is false but (R) is true.

Hint: For a spontaneous reaction,

∆ G

value

is

negative

Spontaneous processes are those that can proceed without any outside intervention. Spontaneous processes are irreversible.

For a spontaneous,

∆ H

value

is

negative

and

∆ S

value is positive. Thus, a decrease in enthalpy is a contributing factor to

spontaneity. Hence, both assertion and reason are true and the reason is not the correct explanation of assertion.