NEET-UG and JEE Main Chemistry · Class 11
Third law of thermodynamics — NEET & JEE Questions
Third law of thermodynamics is a topic in Chemical Thermodynamics, a Class 11 Chemistry chapter of the NEET-UG and JEE Main syllabus. TestBudy holds 12 published NEET-UG and JEE Main questions on Third law of thermodynamics, each with the marking scheme of the real paper.
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Third law of thermodynamics MCQs with solutions
10 of the 12 published questions on this topic, exactly as they appear in a test. Answers and worked solutions come with your result rather than on this page.
The third law of thermodynamics states that the entropy of a perfect crystal at absolute zero is
- A. zero
- B. infinite
- C. one joule per kelvin
- D. equal to its enthalpy
The third law is especially useful because it provides
- A. a reference for absolute entropy values
- B. a direct formula for pressure
- C. a definition of enthalpy
- D. a law for reaction rate
The phrase 'perfect crystal' in the third law implies
- A. complete structural order
- B. maximum disorder
- C. a liquid state
- D. a gas with random positions
At temperatures above 0 K, the entropy of a substance is generally
- A. greater than or equal to its 0 K reference value
- B. always exactly zero
- C. necessarily negative
- D. undefined
Which substance is the best ideal example for assigning zero entropy at 0 K?
- A. A perfect crystalline solid
- B. A gas with random molecular positions
- C. A liquid mixture
- D. A disordered glass
Why can a real crystal with orientational disorder at very low temperature have residual entropy?
- A. More than one microscopic arrangement may remain accessible
- B. Its temperature is necessarily above 1000 K
- C. Entropy cannot exist in solids
- D. The third law requires all real crystals to have zero entropy regardless of disorder
Which process would normally increase the entropy of a substance most clearly?
- A. Heating a perfect crystal from near 0 K
- B. Cooling a gas toward 0 K
- C. Increasing structural order
- D. Freezing a liquid
The absolute entropy of a substance at temperature T can conceptually be obtained by
- A. starting from the 0 K reference and summing entropy changes on heating and phase transitions
- B. setting entropy equal to enthalpy
- C. measuring only pressure
- D. using atomic number
A perfectly ordered crystal and a disordered solid are both hypothetically at 0 K. Which statement best matches third-law reasoning?
- A. The perfect crystal has zero entropy, while disorder may produce residual entropy
- B. Both must have infinite entropy
- C. The disordered solid must have lower entropy
- D. Order has no relation to entropy
Why is absolute zero important in the third law?
- A. It provides the limiting reference state for perfect-crystal entropy
- B. It is the temperature of maximum entropy
- C. It defines boiling point
- D. It eliminates the need for heat capacities
Common mistakes in Third law of thermodynamics
Recorded against questions in this topic that are not shown above, so none of these points at an answer you can see on this page.
- Confuses the thermodynamic laws because both discuss state functions.
- Applies the perfect-crystal zero entropy to a system with persistent configurational disorder.
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