This set of Physical Chemistry Multiple Choice Questions & Answers (MCQs) focuses on “Fundamental Laws of Thermodynamics”.
1. What is the mathematical form of the first law of thermodynamics?
a) ΔH = CP ΔT
b) ΔH = ΔU + Δ(PV)
c) ΔEK + ΔEP = 0
d) ΔU = Q – W
View Answer
Explanation: First law of thermodynamics states that the change in the internal energy (ΔU) of a closed system is equal to the amount of heat (Q) supplied to the system, minus the amount of work (W) done by the system.
2. Carnot’s theorem states that all the heat engines between two reservoirs are less efficient than the Carnot heat engine.
a) True
b) False
View Answer
Explanation: For a given heat reservoirs no engine can have a thermal efficiency higher than that of a Carnot’s engine. Every Carnot heat engine is equally efficient.
3. The thermal efficiency of the Carnot engine depends upon ____________
a) Pressure
b) Heat capacity
c) Temperature levels
d) Speed
View Answer
Explanation: The thermal efficiency of the Carnot engine depends only on the temperature levels and not on the working substance of the engine.
4. The area under temperature – entropy curve represents _________
a) Heat absorbed or heat rejected
b) heat rejected
c) heat absorbed
d) Does not represent anything
View Answer
Explanation: It represents changes to temperature and specific entropy in a thermodynamic process or cycle.
5. What is the Zeroth law of thermodynamics?
a) The entropy of the system at absolute zero is close to zero
b) The sum of the entropies of thermodynamic system increases
c) When energy passes the system’s internal energy changes
d) If two thermodynamic systems are each in thermal equilibrium with a third, then they are in thermal equilibrium
View Answer
Explanation: Zeroth law of thermodynamics states that there is no change in observable state over time and no flow occurs.
6. The efficiency of dual combustion cycle is _________
a) Greater than diesel cycle and greater than Otto cycle
b) Greater than diesel cycle
c) Less than diesel cycle
d) Less than diesel cycle and greater than Otto cycle
View Answer
Explanation: Diesel cycle is more efficient than Otto cycle. Otto cycle has lower compression ratio than the Diesel cycle.
7. Brayton cycle is also known as _________
a) Constant pressure cycle
b) Constant volume cycle
c) Constant temperature cycle
d) Constant volume and temperature cycle
View Answer
Explanation: Brayton cycle describes the working of a constant – pressure heat engine. Brayton cycle usually runs as an open system.
8. In an isothermal process, there is no change of enthalpy.
a) True
b) False
View Answer
Explanation: In an isothermal energy change in internal energy and change in PV is zero so there is no change in enthalpy.
9. The gas constant (R) is equal to the difference of two _________
a) Specific heat
b) Temperature
c) Pressure
d) Heat capacities
View Answer
Explanation: The specific heat of gases are CP and CV and their relation with gas constant (R) is CP = CV + R.
10. Select the correct statement.
a) Absolute pressure = Gauge pressure
b) Absolute pressure = Atmospheric pressure
c) Absolute pressure = Gauge pressure + Atmospheric pressure
d) Atmospheric pressure = Gauge pressure + Absolute pressure
View Answer
Explanation: Absolute pressure is equal to the gauge pressure plus atmospheric pressure. Gauge pressure is zero referenced against ambient air pressure, so it is equal to the absolute pressure minus atmospheric pressure.
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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