NEET Solved Paper 2014 Question 12
Question: Which of the following statements is correct for the spontaneous absorption of a gas? [AIPMT 2014]
Options:
A) $ \Delta S $ is negative and therefore, $ \Delta H $ should be highly positive
B) $ \Delta S $ is negative and therefore, $ \Delta H $ should be highly negative
C) $ \Delta S $ is positive and therefore, AH should be negative
D) $ \Delta S $ is positive and therefore, $ \Delta H $ should also be highly positive.
Show Answer
Answer:
Correct Answer: A
Solution:
$ \Delta S $ [change in entropy] and $ \Delta H $ [change in enthalpy] are related by the equation
$ \Delta G=\Delta H-T\Delta S $ [here, $ \Delta G $ = change in Gibbs free energy] For adsorption of a gas,
$ \Delta S $ is negative because randomness decreases.
Thus, in order to make $ \Delta G $ negative [for spontaneous reaction], $ \Delta H $ must be highly negative.
Hence, for the adsorption of a gas, if ] $ \Delta S $ is negative, therefore, $ \Delta H $ should be highly negative.
BETA
