Thermodynamics

Consider the following reaction : 2A(g) + B(g) 2D(g) U = −10 kJ mol-1 and S = −44 J K-1 at 298 K. Identify the correct option with G for the reaction and spontaneity of the reaction at 298 K. (Given : R = 8.31 J mol-1 K-1)

1. +0.63568 kJ mol-1, non-spontaneous
2. −0.63568 kJ mol-1, spontaneous
3. −1.635 kJ mol-1, spontaneous
4. +1.635 kJ mol-1, non-spontaneous

A protein undergoes reversible thermal denaturation from its initial state N to denatured state D according to N D. At 60 C, the concentrations of both N and D are equal at equilibrium, and the standard enthalpy change of denaturation is 666 kJ mol-1. The standard entropy change ( S in kJ K-1 mol-1) of the protein upon denaturation at 60 C is closest to

1. 11.1
2. 2.0
3. 2000.0
4. 333.0

For a given reaction, H = 35.5 kJ mol-1 and S = 83.6 J K-1 mol-1. The reaction is spontaneous at (Assume that H and S do not vary with temperature.)

1. T > 425 K
2. all temperatures
3. T > 298 K
4. T < 425 K

Which of the following statements is correct for a reversible process in a state of equilibrium?

1. G = -2.30 RT K
2. G = 2.30 RT K
3. G = -2.30 RT K
4. G = 2.30 RT K

For the reaction, X2O4(l) 2XO2(g) = 2.1 kcal, S = 20 cal K-1 at 300 K Hence, is

1. 2.7 kcal
2. -2.7 kcal
3. 9.3 kcal
4. -9.3 kcal

In which of the following reactions, standard reaction entropy change ( S ) is positive and standard Gibb's energy change ( G ) decreases sharply with increasing temperature ?

1. C(graphite)+ 12O2(g) CO(g)
2. CO(g)+ 12O2(g) CO2(g)
3. Mg(s)+ 12O2(g) MgO(s)
4. 12C(graphite)+ 12O2(g) 12CO2(g)

For vaporization of water at 1 atmospheric pressure, the values of H and S are 40.63 kJ mol-1 and 108.8 J K-1 mol-1, respectively. The temperature when Gibbs energy change ( G) for this transformation will be zero, is

1. 273.4 K
2. 393.4 K
3. 373.4 K
4. 293.4 K

Standard entropies of X2, Y2 and XY3 are 60, 40 and 50 J K-1 mol-1 respectively. For the reaction 12X2 + 32Y2 XY3, H = -30 kJ, to be at equilibrium, the temperature should be

1. 750 K
2. 1000 K
3. 1250 K
4. 500 K

The values of and for the reaction, C(graphite) + CO2(g) 2CO(g) are 170 kJ and 170 J K-1, respectively. This reaction will be spontaneous at

1. 910 K
2. 1110 K
3. 510 K
4. 710 K

Identify the correct statement for change of Gibbs energy for a system ( Gsystem) at constant temperature and pressure.

1. If Gsystem < 0, the process is not spontaneous.
2. If Gsystem > 0, the process is spontaneous.
3. If Gsystem = 0, the system has attained equilibrium.
4. If Gsystem = 0, the system is still moving in a particular direction.

The enthalpy and entropy change for the reaction: Br2(l) + Cl2(g) 2BrCl(g) are 30 kJ mol-1 and 105 J K-1 mol-1 respectively. The temperature at which the reaction will be in equilibrium is

1. 300 K
2. 285.7 K
3. 273 K
4. 450 K

A reaction occurs spontaneously if

1. T S < H and both H and S are +ve
2. T S > H and H is +ve and S is −ve
3. T S > H and both H and S are +ve
4. T S = H and both H and S are +ve

Standard enthalpy and standard entropy changes for the oxidation of ammonia at 298 K are -382.64 kJ mol-1 and -145.6 J K-1 mol-1, respectively. Standard Gibbs energy change for the same reaction at 298 K is

1. -221.1 kJ mol-1
2. -339.3 kJ mol-1
3. -439.3 kJ mol-1
4. -523.2 kJ mol-1

The densities of graphite and diamond at 298 K are 2.25 and 3.31 g cm-3, respectively. If the standard free energy difference ( G ) is equal to 1895 J mol-1, the pressure at which graphite will be transformed into diamond at 298 K is

1. 11.14 108 Pa
2. 11.14 107 Pa
3. 11.14 106 Pa
4. 11.14 105 Pa