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Chemical Engineering Thermodynamics MCQ Questions & Answers | Chemical Engineering

Learn Chemical Engineering Thermodynamics MCQ questions & answers are available for a Chemical Engineering students to clear GATE exams, various technical interview, competitive examination, and another entrance exam. Chemical Engineering Thermodynamics MCQ question is the important chapter for a Chemical Engineering and GATE students. Page-8 section-5

Each section contains 100 MCQs on Chemical Engineering Thermodynamics .
71
Specific __________ does not change during phase change at constant temperature and pressure.
Discuss
Answer & Solution
Answer: Option B
Solution:
We know specific Gibbs free energy is:
$$dG=vdp-sdT$$     for pure substance so, under constant temperature and pressure the gibbs free energy is equal to zero.
72
Tea kept in a thermos flask is vigorously shaken. If the tea is considered as a system, then its temperature will
Discuss
Answer & Solution
Answer: Option A
Solution:
As thermos flask is insulated no heat energy added or taken from the system so, by first law of thermodynamics we can write $$dU = - \delta W$$   as we work done on the system is negative so, the internal energy will be positive. And therefore there will be a raise in temperature.
73
Which of the following is an extensive property of a system?
Discuss
Answer & Solution
Answer: Option A
Solution:
Heat capacity is an extensive property as it dependent on the extent or amount of the substance.
74
The expression for entropy change, ΔS = nCp.ln$$\left( {\frac{{{{\text{T}}_2}}}{{{{\text{T}}_1}}}} \right),$$  is valid for the __________ of a substance.
Discuss
Answer & Solution
Answer: Option D
Solution:
Actually the Entropy of an ideal gas is given by:
$$\Delta S = \int_{{T_i}}^{{T_f}} {} \frac{{{C_p}dT}}{T} - nR\ln \left( {\frac{{{P_f}}}{{{P_i}}}} \right).$$
$$ \Rightarrow $$  it depends upon both temperature and pressure.
Under constant pressure process we can write $$\Delta S = {C_p}.\ln \left( {\frac{{{T_f}}}{{{T_i}}}} \right).$$    The final temperature can be greater or lesser than the initial temperature.
75
When a system in equilibrium is subjected to a change in temperature, pressure or concentration, the equilibrium is displaced in a direction which tends to undo the effect of the change. This is called the
Discuss
Answer & Solution
Answer: Option A
Solution:
Le Chatelier's principle states that a system will react to a change (disturbing the equilibrium) in such a way that it minimizes the change.
76
Dryness fraction of wet steam is defined as the ratio of mass of vapour in the mixture to the mass of mixture __________ calorimeter is not used for measuring the dryness fraction of steam.
Discuss
Answer & Solution
Answer: Option A
Solution:
Bomb calorimeter is usually used to measure the calorific values of the fuels.
77
Steam undergoes isentropic expansion in a turbine from 5000 kPa and 400°C (entropy = 6.65 kJ/kg.K) to 150 kPa) (entropy of saturated liquid = 1.4336 kJ/kg.K, entropy of saturated vapour = 7.2234 kJ/kg.K) The exit condition of steam is
Discuss
Answer & Solution
Answer: Option A
Solution:
For an isentropic process $$s{\text{ }}initial = s{\text{ }}final{\text{ }}\left( {exit} \right)$$
$$\eqalign{ & \Rightarrow 6.65 = {S_{liq}} + x\left( {{S_{liq}} - {\text{ }}{S_v}} \right) \cr & \Rightarrow 6.63 = 1.4336 + x\left( {7.2234 - 1.4336} \right) \cr & \Rightarrow x = 0.9 \cr} $$
So, we are getting partially condensed vapour with quality = 0.9.
78
The extensive properties are
Discuss
Answer & Solution
Answer: Option C
Solution:
Extensive properties are those which depend on the extent or amount of the substance present.
79
The intensive properties are
Discuss
Answer & Solution
Answer: Option C
Solution:
Intensive properties are those which doesn’t depends on the extent or amount of the substance present.
80
Which of the following has the least thermal efficiency?
Discuss
Answer & Solution
Answer: Option A
Solution:
Steam engine has the least thermal efficiency as some of the heat is lost in warming the vessel.