Physical Chemistry Questions and Answers – Gas Equations

This set of Physical Chemistry Multiple Choice Questions & Answers (MCQs) focuses on “Gas Equations”.

1. Which one of the following formula is true for Second Law of Thermodynamics?
a) dS ≥ Q/T
b) dU = Q – W
c) dU ≤ Q – W
d) dS = Q/T
View Answer

Answer: a
Explanation: The second law of thermodynamics states that entropy changes of a closed system obeys the following equation inequality dS ≥ Q / T.

2. What is the fundamental equation of thermodynamics?
a) dU ≤ 0
b) dU ≤ TdS – pdV
c) dS ≤ 0
d) dU = TdS – pdV
View Answer

Answer: d
Explanation: The fundamental equation of thermodynamics shows a little change in internal energy in terms of entropy and volume for a closed system. This relation applies to a change in a closed system.

3. What is the equation of an ideal gas?
a) P V = K
b) P V = n K T
c) P V = m R T
d) P V = n R T
View Answer

Answer: a
Explanation: The ideal gas equation is P V = n R T, where R is universal gas constant. It is used to calculate either the pressure, volume or number of moles.

4. Select the correct statement for an irreversible process.
a) No gain of heat
b) Gain of heat
c) Loss of heat
d) No loss of heat
View Answer

Answer: c
Explanation: Some amount of the energy will be used as the molecules when they change from one state to another. During this transformation, there will be a certain amount of heat loss.

5. The Constant-Volume cycle also known as __________
a) Brayton cycle
b) Otto cycle
c) Rankine cycle
d) Stirling cycle
View Answer

Answer: b
Explanation: Otto cycle describes the functioning of a spark ignition piston engine. This cycle is also known as Constant-Volume cycle.

6. What is the value of Gas Constant R?
a) 8.934 J mol−1⋅ K−1
b) 8.134 J mol−1⋅ K−1
c) 8.314 J mol−1⋅ K−1
d) 7.306 J mol−1⋅ K−1
View Answer

Answer: c
Explanation: The gas constant is a physical constant that features in many equations. The value of gas constant is R = 8.314 J mol−1⋅ K−1

7. When does the highest temperature occurs in the Brayton cycle?
a) At the end of combustion process
b) When the ambient air is drawn to the compressor
c) At the time of heat rejection
d) During expansion
View Answer

Answer: a
Explanation: The higher temperature occurs at the end of the combustion process, which limits the pressure ratio.

8. What is an Adiabatic process?
a) In which pressure remains constant
b) Occurs without transfer of heat or matter
c) In which volume remains constant
d) Proceeds without any change in enthalpy
View Answer

Answer: b
Explanation: An Adiabatic process occurs without transfer of heat or matter. In this process, no energy is transferred by heat.

9. What is the entropy of the universe?
a) Zero
b) Continually increasing
c) Continually decreasing
d) Infinite
View Answer

Answer: b
Explanation: The entropy of the universe keeps increasing. In universe, there is a consistent creation of organization, so there is a constant increase in entropy. The second law of thermodynamics states that “The entropy of the universe tends to be maximum.”

10. What is Raoult’s Law?
a) Vapor pressure of an ideal solution is proportional to the mole fraction
b) The enthalpy change for the reactions is the sum of the all changes
c) It is used to calculate maximum reversible work
d) No heat flows through them when the path is permeable
View Answer

Answer: a
Explanation: Raoult’s law states that the freezing and boiling point of solution are depressed and elevated to that of the pure solvent by an amount proportional to the mole fraction of the solute.

Sanfoundry Global Education & Learning Series – Physical Chemistry.

To practice all areas of Physical Chemistry, here is complete set of Multiple Choice Questions and Answers.

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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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