Q1 · June 2021 · 2 marks
The maximum number of phases that can be simultaneously in equilibrium for a one component system is
- (a) 1
- (b) 2
- (c) 3
- (d) 4
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Answer: (c)
CSIR NET Chemical Science — Chemical Thermodynamics previous year questions
51 questions · 2011–2021 · all with verified answer · last checked 2026-11-06
Q2 · June 2021 · 2 marks
When yellow phosphorous is converted to red phosphorous, the entropy and volume of the system do not change. The order of this phase transition is most likely to be
- (a) 3
- (b) 2
- (c) 1
- (d) 0
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Answer: (b)
Q3 · June 2019 · 2 marks
The chemical potential (\mu) of a 2 molar \mathrm{Na_2SO_4} solution is expressed in terms of mean ionic activity co-efficient (\gamma_\pm) as
- (a) \mu^0 + 5RT\ln 2 + 3RT\ln\gamma_\pm
- (b) \mu^0 + 53T\ln 2 + 3RT\ln\gamma_\pm
- (c) \mu^0 + +3RT\ln\gamma_\pm
- (d) \mu^0 + +4RT\ln\gamma_\pm
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Answer: (a)
Q4 · Dec 2019 · 2 marks
The excess molar entropy of mixing of liquid A with liquid B is -R\ln 2. The experimentally observed change in entropy upon mixing 1.0 mol of liquid A with 1.0 mol of liquid B is
- (a) -2R\ln 2
- (b) +4R\ln 2
- (c) 0
- (d) +R\ln 2
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Answer: (c)
Q5 · June 2019 · 2 marks
When two moles of liquid A are mixed with two moles of liquid B at 300K, the excess molar Gibbs energy of the solution is -1.5 \mathrm{~kJ} \mathrm{~mol}^{-1}. The corresponding value of Gibbs energy of mixing (in kJ ) is closest to ( \mathrm{R}=8.3 \mathrm{~J} \mathrm{~K}^{-1} \mathrm{~mol}^{-1} )
- (a) -12.9
- (b) -6.0
- (c) -1.5
- (d) -0.9
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Answer: (a)
Q6 · June 2019 · 2 marks
A sample of 2.0 moles of \mathrm{O}_{2}(\mathrm{~g}) (assumed ideal) at 500 K is expanded from 5 L to 50 L under adiabatic and reversible conditions. The change in its internal energy (in kJ) is close to
R=8.3 \mathrm{~K}^{-1} \mathrm{~mol}^{-1} ; \mathrm{C}_{\mathrm{V}, \mathrm{~m}}=\frac{5}{2} \mathrm{R}
- (a) -22.5
- (b) -12.5
- (c) -19.1
- (d) -7.5
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Answer: (b)
Q7 · June 2019 · 2 marks
The chemical potential (\mu) of a 2 molar \mathrm{Na_2SO_4} solution is expressed in terms of mean ionic activity co-efficient (\gamma_\pm) as
- (a) \mu_0 + 5RT\ln 2 + 3RT\ln\gamma_\pm
- (b) \mu_0 + 53T\ln 2 + 3RT\ln\gamma_\pm
- (c) \mu_0 + +3RT\ln\gamma_\pm
- (d) \mu_0 + +4RT\ln\gamma_\pm
Show answer
Answer: (a)
Q8 · Dec 2019 · 2 marks
(C_p - C_v) for a non-ideal gas differs from (C_p - C_v) for a perfect gas by the expression (1) \left(\frac{\partial P}{\partial T}\right)_V\left(\frac{\partial U}{\partial P}\right)_S (2) \left(\frac{\partial V}{\partial T}\right)_P\left(\frac{\partial U}{\partial V}\right)_T (3) -\frac{1}{T}\left(\frac{\partial V}{\partial T}\right)_P\left(\frac{\partial U}{\partial V}\right)_T (4) \left(\frac{\partial P}{\partial T}\right)_V\left(\frac{\partial U}{\partial T}\right)_P
- (a) 1
- (b) 2
- (c) 3
- (d) 4
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Answer: (b)
Q9 · Dec 2019 · 2 marks
A monatomic perfect gas undergoes expansion from (p_1, V_1) to (p_2, V_2) under isothermal or adiabatic conditions. The pressure of the gas will fall more rapidly under adiabatic conditions because
- (a) p \propto \frac{1}{V}
- (b) p \propto \frac{1}{V^{7/5}}
- (c) p \propto \frac{1}{V^{3/2}}
- (d) p \propto \frac{1}{V^{5/3}}
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Answer: (d)
Q10 · Dec 2019 · 2 marks
For a van der Waals gas, the partial derivative is \left(\frac{\partial U}{\partial V}\right)_T
- (a) \frac{V_m}{a}
- (b) \frac{V_m^2}{a}
- (c) \frac{a}{V_m^2}
- (d) \frac{a}{V_m}
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Answer: (c)
Q11 · Dec 2019 · 2 marks
The excess molar entropy of mixing of liquid A with liquid B is -R\ln 2. The experimentally observed change in entropy upon mixing 1.0 mol of liquid A with 1.0 mol of liquid B is
- (a) -2R\ln 2
- (b) +4R\ln 2
- (c) 0
- (d) +R\ln 2
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Answer: (c)
Q12 · Dec 2019 · 2 marks
The change in chemical potential (in J) of one mole of an ideal gas, when it is compressed isothermally at 300 K from 1.0 atm to 2.0 atm, is closest to (ln 2 = 0.69)
- (a) 1225
- (b) 1725
- (c) 2425
- (d) 2725
Show answer
Answer: (c)
Q13 · Dec 2018 · 2 marks
For a closed system in the absence of non-PV work, the correct statement is
- (a) \mathbf{d U}=\mathbf{T d S}-\mathbf{P d V}
- (b) \mathbf{d G}=\mathbf{V d P}+\mathbf{S d T}
- (c) \mathbf{d U}=\mathbf{T d S}+\mathbf{P d V}
- (d) \mathbf{d U}=\mathbf{V d P}-\mathbf{S d T}
Show answer
Answer: (a)
Q14 · Dec 2018 · 2 marks
The volume change in a certain phase transition is 2.0\,\mathrm{mL\,mol^{-1}} at the transition point. From this, we may conclude that the transition is most likely to
- (a) First order phase transition
- (b) Second order phase transition
- (c) Third order phase transition
- (d) λ phase transition
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Answer: (a)
Q15 · Dec 2018 · 2 marks
Consider a phase transition between two incompressible phases. The correct statement among the following is
- (a) The transition is independent of pressure
- (b) The transition is independent of temperature
- (c) The entropy of such transition is always zero
- (d) The enthalpy of such transition is always non-zero
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Answer: (a)
Q16 · June 2017 · 2 marks
The correct statement for any cyclic thermodynamic process is
- (a) \oint dq = 0
- (b) \oint dw = 0
- (c) \oint dU = 0
- (d) \oint V dq = 0
Show answer
Answer: (c)
Q17 · Dec 2017 · 2 marks
Enthalpy is equal to
- (a) TS + PV + \sum \mu_i n_i
- (b) TS + \sum \mu_i n_i
- (c) \sum \mu_i n_i
- (d) PV + \sum \mu_i n_i
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Answer: (b)
Q18 · June 2017 · 2 marks
A phase transition process is always
- (a) isothermal - isoentropic
- (b) isochoric - isothermal
- (c) isobaric - isochoric
- (d) isothermal - isobaric
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Answer: (d)
Q19 · June 2017 · 2 marks
The correct statement for any cyclic thermodynamic process is
- (a) dq = 0
- (b) dw = 0
- (c) dU = 0
- (d) Vdq = 0
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Answer: (c)
Q20 · June 2017 · 2 marks
The fugacity of a real gas is less than the pressure (P) of an ideal gas at the same temperature (T) only when (T_b is the Boyle temperature of the real gas)
- (a) high P, T < T_b
- (b) low P, T < T_b
- (c) high P, T > T_b
- (d) low P, T > T_b
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Answer: (b)
Q21 · June 2017 · 2 marks
The minimum work required by an engine to transfer 5 J of heat from a reservoir at 100 K to one at 300 K is
- (a) 5 J
- (b) 10 J
- (c) 15 J
- (d) 20 J
Show answer
Answer: (b)
Q22 · Dec 2017 · 2 marks
Enthalpy is equal to
- (a) TS + PV + \Sigma\mu_i n_i
- (b) TS + \Sigma\mu_i n_i
- (c) \Sigma\mu_i n_i
- (d) PV + \Sigma\mu_i n_i
Show answer
Answer: (b)
Q23 · Dec 2016 · 2 marks
The equation of state for one mole of a gas is given by P(V - b) = RT, where b and R are constants. The value of \left(\frac{\partial H}{\partial P}\right)_T is
- (a) V - b
- (b) b
- (c) 0
- (d) \frac{RT}{P} + b
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Answer: (b)
Q24 · June 2016 · 2 marks
\left(\frac{\partial H}{\partial P}\right)_T has the dimension of
- (a) pressure
- (b) volume
- (c) temperature
- (d) heat capacity
Show answer
Answer: (b)
Q25 · June 2016 · 2 marks
For an ideal gas at 300 K
- (a) \left(\frac{\partial U}{\partial V}\right)_T = 0
- (b) \left(\frac{\partial U}{\partial T}\right)_V = 0
- (c) \left(\frac{\partial H}{\partial T}\right)_P = 0
- (d) \left(\frac{\partial G}{\partial T}\right)_P = 0
Show answer
Answer: (a)
Q26 · Dec 2016 · 2 marks
The parameter which always decreases during a spontaneous process at constant S and V, is
- (a) U
- (b) H
- (c) C_p
- (d) q
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Answer: (a)
Q27 · Dec 2016 · 2 marks
Triple point pressure of substances A, B, C and D are 0.2, 0.5, 0.8 and 1.2 bar, respectively. The substance which sublimes under standard conditions on increasing temperature is
- (a) A
- (b) B
- (c) C
- (d) D
Show answer
Answer: (d)
Q28 · Dec 2016 · 2 marks
The partial derivative \left(\frac{\partial T}{\partial V}\right)_P is equal to
- (a) -\left(\frac{\partial P}{\partial S}\right)_T
- (b) -\left(\frac{\partial P}{\partial S}\right)_V
- (c) -\left(\frac{\partial P}{\partial S}\right)_n
- (d) -\left(\frac{\partial P}{\partial S}\right)_H
Show answer
Answer: (a)
Q29 · June 2015 · 2 marks
Heat capacity of a species is independent of temperature if it is
- (a) tetratomic
- (b) triatomic
- (c) diatomic
- (d) monatomic
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Answer: (d)
Q30 · June 2015 · 2 marks
A thermodynamic equation that relates the chemical potential to the composition of a mixture is known as
- (a) Gibb's-Helmholtz equation
- (b) Gibbs-Duhem equation
- (c) Joule-Thomson equation
- (d) Debye-Huckel equation
Show answer
Answer: (b)
Q31 · Dec 2015 · 2 marks
The value of \quad \Delta \mathrm{U}-\Delta \mathrm{H} for the reaction \quad \mathrm{Fe}_{2} \mathrm{O}_{3}(\mathrm{~s})+3 \mathrm{C}(\mathrm{s}) \rightarrow 2 \mathrm{Fe}(\mathrm{s})+3 \mathrm{CO}(\mathrm{g}) is
- (a) -3RT
- (b) +3RT
- (c) +RT
- (d) -RT
Show answer
Answer: (a)
Q32 · Dec 2015 · 2 marks
\Delta H of a reaction is equal to slope of the plot of
- (a) \Delta G vs (1/T)
- (b) \Delta G vs T
- (c) (\Delta G/T) vs T
- (d) (\Delta G/T) vs (1/T)
Show answer
Answer: (d)
Q33 · June 2014 · 2 marks
In a bomb calorimeter, the combustion of 0.5 g of compound A (molar mass = 50 \mathrm{g\,mol^{-1}}) increased the temperature by 4 K. If the heat capacity of the calorimeter along with that of the material is 2.5 \mathrm{kJ\,K^{-1}}, the molar internal energy of combustion, in kJ, is
- (a) 1000
- (b) -1000
- (c) 20
- (d) -20
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Answer: (b)
Q34 · June 2014 · 2 marks
The number of phases, components and degrees of freedom, when Ar is added to an equilibrium mixture of NO, \mathrm{O_2} and \mathrm{NO_2} in gas phase are, respectively,
- (a) 1, 3, 5
- (b) 1, 4, 5
- (c) 1, 3, 4
- (d) 1, 4, 4
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Answer: (c)
Q35 · Dec 2014 · 2 marks
For a process in a closed system, temperature is equal to
- (a) \left(\frac{\partial H}{\partial P}\right)_{S}
- (b) -\left(\frac{\partial A}{\partial V}\right)_{T}
- (c) \left(\frac{\partial G}{\partial P}\right)_{T}
- (d) \left(\frac{\partial H}{\partial S}\right)_{P}
Show answer
Answer: (d)
Q36 · Dec 2014 · 2 marks
Given the following two relations,
x_{1} d \mu_{1}+x_{2} d \mu_{2}=0
And x_{1} d \tilde{V}_{1}+x_{2} d \tilde{V}_{2}=0 for a binary liquid mixture at constant temperature and pressure, the true statement is that, - (a) Both the relations are correct
- (b) Relation A is correct, but B is not
- (c) Relation B is correct, but A is not
- (d) Both the relations are incorrect, except for very dilute solutions.
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Answer: (a)
Q37 · Dec 2014 · 2 marks
At high pressure, the fugacity coefficient of a real gas is greater than one, because
- (a) Attractive term overweighs the repulsive term
- (b) Repulsive term overweighs the attractive term
- (c) Repulsive term is equal to the attractive term
- (d) The system is independent of both the attractive and repulsive terms
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Answer: (b)
Q38 · June 2013 · 2 marks
The lowest pressure at which the liquid phase of a pure substance can exist is known as
- (a) critical point pressure
- (b) super-incumbent pressure
- (c) triple-point pressure
- (d) saturation vapour pressure.
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Answer: (c)
Q39 · June 2013 · 2 marks
Which of the following statements is true for a cyclic process?
- (a) \partial q = 0
- (b) \partial w = 0
- (c) Heat can be completely converted into work
- (d) Work can be completely converted into heat
Show answer
Answer: (d)
Q40 · Dec 2013 · 2 marks
The correct thermodynamics relation among the following is
- (a) \left(\frac{\partial U}{\partial V}\right)_{S}=-P
- (b) \left(\frac{\partial H}{\partial V}\right)_{S}=-P
- (c) \left(\frac{\partial G}{\partial V}\right)_{S}=-P
- (d) \left(\frac{\partial A}{\partial V}\right)_{S}=-P
Show answer
Answer: (a)
Q41 · Dec 2013 · 2 marks
The heat capacity of 10 mol of an ideal gas at a certain temperature is 300\,\mathrm{JK^{-1}} at constant pressure. The heat capacity of the same gas at the same temperature and at constant volume would be
- (a) 383\,\mathrm{JK^{-1}}
- (b) 217\,\mathrm{JK^{-1}}
- (c) 134\,\mathrm{JK^{-1}}
- (d) 466\,\mathrm{JK^{-1}}
Show answer
Answer: (b)
Q42 · Dec 2013 · 2 marks
The boiling point of a solution of non-volatile solid is higher than that of the pure solvent. It always indicates that
- (a) the enthalpy of the solution is higher than that of the pure solvent
- (b) the entropy of the solution is higher than that of the pure solvent
- (c) the Gibbs free energy of the solution is higher than that of the pure solvent
- (d) the internal energy of the solution is higher than that of the pure solvent
Show answer
Answer: (b)
Q43 · June 2012 · 2 marks
The vapour of a pure substance, when cooled under a pressure less than its triple-point pressure,
- (a) Liquefies
- (b) Liquefies first and then solidifies
- (c) Solidifies directly
- (d) Remains unchanged
Show answer
Answer: (c)
Q44 · June 2012 · 2 marks
The quantities, which are held fixed in a canonical ensemble are
- (a) N, T and P
- (b) V, T and N
- (c) N, V and E
- (d) \mu, V and P
Show answer
Answer: (b)
Q45 · June 2012 · 2 marks
An ideal gas was subjected to a reversible, adiabatic, expansion and then its initial volume was restored by a reversible, isothermal compression. If ' q ' denotes the heat added to the system and ' w ' the work done by the system, then
- (a) \mathbf{w}<\mathbf{0}, q <\mathbf{0}
- (b) \mathbf{w}>\mathbf{0}, \mathbf{q}<\mathbf{0}
- (c) \mathbf{w}<\mathbf{0}, \mathbf{q}>\mathbf{0}
- (d) \mathbf{w}>\mathbf{0}, \mathbf{q}>\mathbf{0}
Show answer
Answer: (b)
Q46 · Dec 2012 · 2 marks
The internal pressure (\partial U/\partial V)_T of a real gas is related to the compressibility factor Z = p\tilde{V}/RT by [where, \tilde{V} is the molar volume]
- (a) (\partial U/\partial V)_T = RT(\partial Z/\partial V)_T
- (b) (\partial U/\partial V)_T = RT(\tilde{V}Z)
- (c) (\partial U/\partial V)_T = (RT_2/\tilde{V})(\partial Z/\partial T)_V
- (d) (\partial U/\partial V)_T = (\tilde{V}/RT_2)(\partial Z/\partial T)_V
Show answer
Answer: (c)
Q47 · Dec 2011 · 2 marks
For the liquid \rightleftharpoons vapour equilibrium of a substance \frac{dP}{dT} at 1 bar and 400 K is 8 \times 10^{-3} bar \mathrm{K^{-1}}. If the molar volume in the vapour form is 200 \mathrm{L\,mol^{-1}} and the molar volume in the liquid form is negligible, the molar enthalpy of vapourisation is (1.0 bar L = 100 J)
- (a) 640 \mathrm{kJ\,mol^{-1}}
- (b) 100 \mathrm{kJ\,mol^{-1}}
- (c) 80 \mathrm{kJ\,mol^{-1}}
- (d) 64 \mathrm{kJ\,mol^{-1}}
Show answer
Answer: (d)
Q48 · June 2011 · 2 marks
A process is carried out at constant volume and at constant entropy. It will be spontaneous if:
- (a) \Delta G < 0
- (b) \Delta H < 0
- (c) \Delta U < 0
- (d) \Delta A < 0
Show answer
Answer: (c)
Q49 · 2011-2020 · 2 marks
The chemical potential of component 1 in a solution of binary mixture is \mu_{1}=\mu_{1}^{o}+R T \ln p_{1}, when p_{1} is the partial pressure of component 1 vapour phase. The standard state \mu_{1}^{o} is:
- (a) Independent of temperature and pressure
- (b) Depends on temperature and pressure both
- (c) Depends on temperature only
- (d) Depends on pressure only
Show answer
Answer: (c)
Q50 · Dec 2011 · 2 marks
For a system of constant composition, the pressure (P) is given by.
- (a) -\left(\frac{\partial U}{\partial S}\right)_V
- (b) -\left(\frac{\partial U}{\partial V}\right)_S
- (c) \left(\frac{\partial V}{\partial S}\right)_T
- (d) \left(\frac{\partial U}{\partial V}\right)_T
Show answer
Answer: (b)
Q51 · Dec 2011 · 2 marks
For the reaction \mathrm{C_2H_4(g) + 3O_2(g) \rightarrow 2CO_2(g) + 2H_2O}(l), the value of \Delta H - \Delta U (in kJ) at 300 K and 1 bar is
- (a) –5.0
- (b) 0.0
- (c) 2.5
- (d) 5.0
Show answer
Answer: (a)
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