Thermodynamic Relations - Thermodynamics - GATE Questions - with Solutions at MSubbu Academy

Thermodynamics - GATE-CH Questions

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Thermodynamic Relations

GATE-CH-1994-4-o-td-1mark

Match the following:

GATE-CH-1989-6-ii-b-td-1mark

Entropy is :

GATE-CH-1991-7-iv-td-2mark

To obtain the integrated form of Clausius-Clapeyron equation \[ \ln \frac {P_2}{P_1} = \frac {\Delta H_V}{R}\left (\frac {1}{T_1} - \frac {1}{T_2} \right ) \] from the exact Clapeyron equation, it is assumed that:

GATE-CH-1993-5-e-td-1mark

Which among the following relations is/are valid ONLY for reversible process undergone by a pure substance?

GATE-CH-1996-1-20-td-1mark

The equation \(dU = TdS - PdV\) is applicable to infinitesimal changes occurring in


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GATE-CH-1997-1-20-td-1mark

The change in Gibbs free energy for vaporization of a pure substance is

GATE-CH-2001-2-4-td-2mark

The Maxwell relation derived from the differential expression for the Helmholtz free energy (\(dA\)) is:

GATE-CH-2001-2-5-td-2mark

At 100oC , water and methylcyclohexane both have vapor pressures of 1.0 atm. Also at 100oC , the latent heats of vaporization of these compounds are 40.63 kJ/mol for water and 31.55 kJ/mol for methylcyclohexane. The vapor pressure of water at 150oC is 4.69 atm. At 150oC , the vapor pressure of methylcyclohexane would be expected to be:

GATE-CH-2002-1-23-td-1mark

Which of the following identities can be most easily used to verify steam table data for superheated steam?

GATE-CH-2007-31-td-2mark

For a pure substance, the Maxwell’s relation obtained from the fundamental property relation \(dU = TdS - PdV\) is


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GATE-CH-2009-6-td-1mark

An ideal gas at temperature \(T_1\) and pressure \(P_1\) is compressed isothermally to pressure \(P_2(>P_1)\) in a closed system. Which ONE of the following is TRUE for internal energy (\(U\)) and the Gibbs free energy (\(G\)) of the gas at the two states?

GATE-CH-2012-7-td-1mark

If the temperature of saturated water is increased infinitesimally at constant entropy, the resulting state of water will be

GATE-CH-2015-7-td-1mark

Three identical closed systems of pure gas are taken from an initial temperature and pressure (\(T_1,P_1\)) to a final state (\(T_2,P_2\)), each by a different path. Which of the following is ALWAYS TRUE for the three systems? (\(\Delta \) represents the change between the initial and final states; \(U, S, G, Q\) and \(W\) are internal energy, entropy, Gibbs free energy, heat added and work done, respectively.)

GATE-CH-2015-9-td-1mark

If \(V,U,S\) and \(G\) represent respectively the molar volume, molar internal energy, molar entropy and molar Gibbs free energy, then match the entries in the Group-1 and Group-2 below and choose the correct option.

Group-1 Group-2
P. \(-(\partial U/\partial V)_S\) I. Temperature
Q. \((\partial G/\partial P)_T\) II. Pressure
R. \(-(\partial G/\partial T)_P\)      III. \(V\)
S. \((\partial U/\partial S)_V\) IV. \(S\)

GATE-XE-2009-E-7-td-1mark

On a \(T\)-\(S\) diagram, the slope of the constant volume line for an ideal gas is


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GATE-XE-2014-E-7-td-1mark

For a superheated vapor that cannot be approximated as an ideal gas, the expression determining a small change in the specific internal energy is

GATE-CH-2015-6-td-1mark

For a pure liquid, the rate of change of vapor pressure with temperature is 0.1 bar/K in the temperature range of 300 to 350 K. If the boiling point of the liquid at 2 bar is 320 K, the temperature (in K) at which it will boil at 1 bar (up to one decimal place is) ____________

GATE-CH-2003-48-49-td-4mark

One kg of saturated steam at 100oC and 1.01325 bar is contained in a rigid walled vessel. It has a volume of 1.673 m3. It cools to 98oC; the saturation pressure is 0.943 bar; one kg of water vapor under these conditions has a volume of 1.789 m3.

(i) The amount of water vapor condensed (in kg) is

{#1}

(ii) The latent heat of condensation (kJ/kg) under these conditions is

{#2}

Solution

GATE-CH-2004-47-td-2mark

The vapor pressure of water is given by \(\displaystyle \ln P^{\text {sat}} = A - \frac {5000}{T}\), where \(A\) is a constant, \(P^{\text {sat}}\) is vapor pressure in atm, and \(T\) is temperature in K. The vapor pressure of water in atm at 50oC is approximately

GATE-CH-2007-33-td-2mark

2 kg of steam in a piston-cylinder device at 400 kPa and 175oC undergoes a mechanically reversible, isothermal compression to a final pressure such that the steam becomes just saturated. What is the work, \(W\) required for the process?

Data:
\(T=175\)oC, \(P = 400\) kPa, \(V=0.503\) m3/kg, \(U=2606\) kJ/kg, \(S = 7.055\) kJ/(kg.K)
\(T=175\)oC, saturated vapor, \(V=0.216\) m3/kg, \(U=2579\) kJ/kg, \(S = 6.622\) kJ/(kg.K)


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GATE-CH-2014-35-td-2mark

Which ONE of the following is CORRECT for an ideal gas in a closed system?

GATE-CH-1996-27-td-5mark

Calculate the change in internal energy (in J) of 25 kmol of \(\ce {CO2}\) gas when it is isothermally expanded from 10132 kPa to 101.32 kPa at 373 K, the corresponding molar volumes being 0.215 m\(^3\)/kmol and 30.53 m\(^3\)/kmol. Assume \(\ce {CO2}\) to obey \((P + 365/V^2)(V - 0.043) = RT\).

GATE-CH-2016-33-td-2mark

A gas obeying the Clausius equation of state is isothermally compressed from 5 MPa to 15 MPa in a closed system at 400 K. The Clausius equation of state is \(\displaystyle P= \frac {RT}{V-b}\) where \(P\) is the pressure, \(T\) is the temperature, \(V\) is the molar volume and \(R\) is the universal gas constant. The parameter \(b\) in the above equation varies with temperature as \(b(T)=b_0+b_1T\) with \(b_0=4\times 10^{-5}\) m3.mol-1and \(b_1=1.35\times 10^{-7}\) m3.mol-1.K-1. The effect of pressure on the molar enthalpy (\(H\)) at a constant temperature is given by \(\displaystyle \left (\frac {\partial H}{\partial P} \right )_T=V-T\left (\frac {\partial V}{\partial T} \right )_P\). Let \(H_i\) and \(H_f\) denote the initial and final molar enthalpies, respectively. The change in the molar enthalpy \(H_f-H_i\) (in J.mol\(^{-1}\), rounded off to the first decimal place) for this process is ____________

GATE-CH-2017-32-td-2mark

The pressure of a liquid is increased isothermally. The molar volume of the liquid decreases from \(50.45\times 10^{-6}\) m3/mol to \(48\times 10^{-6}\) m3/mol during this process. The isothermal compressibility of the liquid is \(10^{-9}\) Pa-1, which can be assumed to be independent of pressure. The change in molar Gibbs free energy of the liquid, rounded to nearest integer, is ____________J/mol.

GATE-CH-0200-2-td-5mark

For 1 mole of a van der Waals gas, evaluate the following coefficients:

  1. \(\displaystyle \left(\frac{\partial P}{\partial T}\right)_V\)

  2. \(\displaystyle \left(\frac{\partial^2 P}{\partial T^2}\right)_V\)

  3. \(\displaystyle \left(\frac{\partial V}{\partial P}\right)_T\)


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Last Modified on: 04-May-2024

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