Spontaneity; entropy and the second law — NEET & JEE Questions

Question 1 · difficulty L1 · recall

The second law of thermodynamics is commonly expressed by stating that the entropy of an isolated system

• A. tends to increase for a spontaneous process
• B. must always decrease
• C. is always zero
• D. is identical to enthalpy

Question 2 · difficulty L2 · understanding

Statement 1 : There is a natural asymmetry between converting work to heat and converting heat to work. Statement 2 : No process is possible in which the sole result is the absorption of heat from a reservoir and its complete conversion into work.

• A. Statement 1 is True, Statement 2 is True; Statement 2 is a CORRECT explanation for Statement 1.
• B. Statement 1 is True, Statement 2 is True; Statement 2 is a NOT CORRECT explanation for Statement 1.
• C. Statement 1 is True, Statement 2 is False.
• D. Statement 1 is False, Statement 2 is True.

Question 3 · difficulty L2 · understanding

Which change generally increases entropy?

• A. Expansion of a gas into a larger volume
• B. Freezing of a liquid
• C. Condensation of a gas
• D. Formation of a more ordered crystal

Question 4 · difficulty L2 · understanding

For a spontaneous process, the entropy change of the universe satisfies

• A. $\Delta S_{univ}>0$
• B. $\Delta S_{univ}<0$
• C. $\Delta S_{univ}=0$ always
• D. $\Delta S_{univ}$ is undefined

Question 5 · difficulty L3 · understanding

One mole of an ideal gas at $$350 \mathrm{~K}$$ is in a $$2.0 \mathrm{~L}$$ vessel of thermally conducting walls, which are in contact with the surroundings. It undergoes isothermal reversible expansion from 2.0 L to $$3.0 \mathrm{~L}$$ against a constant pressure of $$4 \mathrm{~atm}$$. The change in entropy of the surroundings ( $$\Delta \mathrm{S})$$ is ___________ $$\mathrm{J} \mathrm{K}^{-1}$$ (Nearest integer) Given: $$\mathrm{R}=8.314 \mathrm{~J} \mathrm{~K}^{-1} \mathrm{~mol}^{-1}$$.

Question 6 · difficulty L3 · understanding

Ice and water are placed in a closed container at a pressure of 1 atm and temperature 273.15 K . If pressure of the system is increased 2 times, keeping temperature constant, then identify correct observation from following

• A. Liquid phase disappears completely.
• B. The amount of ice decreases.
• C. The solid phase (ice) disappears completely.
• D. Volume of system increases .

Question 7 · difficulty L3 · understanding

For irreversible expansion of an ideal gas under isothermal condition, the correct option is :

• A. $$\Delta$$U $$\ne$$ 0, $$\Delta$$S total = 0
• B. $$\Delta$$U = 0, $$\Delta$$S total = 0
• C. $$\Delta$$U $$\ne$$ 0, $$\Delta$$S total $$\ne$$ 0
• D. $$\Delta$$U = 0, $$\Delta$$S total $$\ne$$ 0

Question 8 · difficulty L3 · application

Which process is most likely to have a positive entropy change for the system?

• A. Melting ice
• B. Freezing water
• C. Condensing steam
• D. Compressing a gas isothermally

Question 9 · difficulty L4 · application

A process has $\Delta S_{system}=+50$ J K$^{-1}$ and $\Delta S_{surroundings}=-20$ J K$^{-1}$. Is the process spontaneous by the entropy criterion?

• A. Yes, because $\Delta S_{universe}=+30$ J K$^{-1}$
• B. No, because surroundings entropy decreases
• C. No, because system entropy is positive
• D. It must be at equilibrium

Question 10 · difficulty L4 · application

At equilibrium in an isolated system, entropy is best described as

• A. maximum with no net spontaneous change
• B. minimum
• C. continuously decreasing
• D. necessarily zero