Thermodynamics

Equal volumes of two monoatomic gases, A and B at same temperature and pressure are mixed. The ratio of specific heats (Cp/Cv) of the mixture will be

1. 0.83
2. 1.50
3. 3.3
4. 1.67

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)

The enthalpy of fusion of water is 1.435 kcal/mol. The molar entropy change for the melting of ice at 0 C is

1. 10.52 cal/(mol K)
2. 21.04 cal/(mol K)
3. 5.260 cal/(mol K)
4. 0.526 cal/(mol K)

Standard enthalpy of vaporisation vapH for water at 100 C is 40.66 kJ mol-1. The internal energy of vaporisation of water at 100 C (in kJ mol-1) is

1. +37.56
2. -43.76
3. +43.76
4. +40.66

Consider the following processes : array|l|c| & H (kJ/mol) \ 12A B & +150 \ 3B 2C + D & -125 \ E + A 2D & +350 \ array For B + D E + 2C, H will be

1. 525 kJ/mol
2. -175 kJ/mol
3. -325 kJ/mol
4. 325 kJ/mol

If the enthalpy change for the transition of liquid water to steam is 30 kJ mol-1 at 27 , the entropy change for the process would be

1. 10 J mol-1 K-1
2. 1.0 J mol-1 K-1
3. 0.1 J mol-1 K-1
4. 100 J mol-1 K-1

Enthalpy change for the reaction, 4H(g) 2H2(g) is -869.6 kJ The dissociation energy of H-H bond is

1. -434.8 kJ
2. -869.6 kJ
3. +434.8 kJ
4. +217.4 kJ

Which of the following is correct option for free expansion of an ideal gas under adiabatic condition ?

1. q = 0, T 0, w = 0
2. q 0, T = 0, w = 0
3. q = 0, T = 0, w = 0
4. q = 0, T < 0, w 0

Three moles of an ideal gas expanded spontaneously into vacuum. The work done will be

1. infinite
2. 3 Joules
3. 9 Joules
4. zero

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

The following two reactions are known Fe2O3(s) + 3CO(g) 2Fe(s) + 3CO2(g); H = -26.8 kJ FeO(s) + CO(g) Fe(s) + CO2(g); H = -16.5 kJ The value of H for the following reaction Fe2O3(s) + CO(g) 2FeO(s) + CO2(g) is

1. +10.3 kJ
2. -43.3 kJ
3. -10.3 kJ
4. +6.2 kJ

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

From the following bond energies : H – H bond energy : 431.37 kJ mol-1 C = C bond energy : 606.10 kJ mol-1 C – C bond energy : 336.49 kJ mol-1 C – H bond energy : 410.50 kJ mol-1 Enthalpy for the reaction, [figure] will be

1. -243.6 kJ mol-1
2. -120.0 kJ mol-1
3. 553.0 kJ mol-1
4. 1523.6 kJ mol-1

Bond dissociation enthalpies of H2, Cl2 and HCl are 434, 242 and 431 kJ mol-1 respectively. Enthalpy of formation of HCl is

1. -93 kJ mol-1
2. 245 kJ mol-1
3. 93 kJ mol-1
4. -245 kJ mol-1

For the gas phase reaction, PCl5(g) PCl3(g) + Cl2(g) which of the following conditions are correct?

1. < 0 and < 0
2. > 0 and < 0
3. = 0 and < 0
4. > 0 and > 0

Which of the following are not state functions? (I) q + w (II) q (III) w (IV) H - TS

1. (I), (II) and (III)
2. (II) and (III)
3. (I) and (IV)
4. (II), (III) and (IV)

Consider the following reactions: (i) H+(aq) + OH-(aq) H2O(l), H = -X1 kJ mol-1 (ii) H2(g) + 12O2(g) H2O(l), H = -X2 kJ mol-1 (iii) CO2(g) + H2(g) CO(g) + H2O(l), H = -X3 kJ mol-1 (iv) C2H2(g) + 52O2(g) 2CO2(g) + H2O(l), H = +X4 kJ mol-1 Enthalpy of formation of H2O(l) is

1. +X3 kJ mol-1
2. -X4 kJ mol-1
3. +X1 kJ mol-1
4. -X2 kJ mol-1

Given that bond energies of H-H and Cl-Cl are 430 kJ mol-1 and 240 kJ mol-1 respectively and Hf for HCl is -90 kJ mol-1, bond enthalpy of HCl is

1. 380 kJ mol-1
2. 425 kJ mol-1
3. 245 kJ mol-1
4. 290 kJ mol-1

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.

Assume each reaction is carried out in an open container. For which reaction will H = E?

1. 2CO(g) + O2(g) 2CO2(g)
2. H2(g) + Br2(g) 2HBr(g)
3. C(s) + 2H2O(g) 2H2(g) + CO2(g)
4. PCl5(g) PCl3(g) + Cl2(g)

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

The enthalpy of hydrogenation of cyclohexene is -119.5 kJ mol-1. If resonance energy of benzene is -150.4 kJ mol-1, its enthalpy of hydrogenation would be

1. -358.5 kJ mol-1
2. -508.9 kJ mol-1
3. -208.1 kJ mol-1
4. -269.9 kJ mol-1

Which of the following pairs of a chemical reaction is certain to result in a spontaneous reaction ?

1. Exothermic and increasing disorder
2. Exothermic and decreasing disorder
3. Endothermic and increasing disorder
4. Endothermic and decreasing disorder

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

The absolute enthalpy of neutralisation of the reaction : MgO(s) + 2HCl(aq) MgCl2(aq) + H2O(l) will be

1. -57.33 kJ mol-1
2. greater than -57.33 kJ mol-1
3. less than -57.33 kJ mol-1
4. 57.33 kJ mol-1

If the bond energies of H-H, Br-Br, and H-Br are 433, 192 and 364 kJ mol-1 respectively, the H for the reaction H2(g) + Br2(g) 2HBr(g) is

1. -261 kJ
2. +103 kJ
3. +261 kJ
4. -103 kJ

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

Considering entropy (S) as a thermodynamic parameter, the criterion for the spontaneity of any process is

1. Ssystem + Ssurroundings > 0
2. Ssystem - Ssurroundings > 0
3. Ssystem > 0 only
4. Ssurroundings > 0 only

The work done during the expansion of a gas from a volume of 4 dm3 to 6 dm3 against a constant external pressure of 3 atm is (1 L atm = 101.32 J)

1. -6 J
2. -608 J
3. +304 J
4. -304 J