Thermodynamics · Question 20

Consider the following data : f H (methane, g) = -X kJ mol-1 Enthalpy of sublimation of graphite = Y kJ mol-1 Dissociation enthalpy of H2 = Z kJ mol-1 The bond enthalpy of C–H bond is given by :

1. X+Y+2Z4
2. X+Y+4Z2
3. -X+Y+Z4
4. X+Y+Z

Resonance in X2Y can be represented as [figure] The enthalpy of formation of X2Y ( X X(g) + 12Y = Y(g) X2Y(g) ) is 80 kJ mol-1. The magnitude of resonance energy of X2Y is kJ mol-1 (nearest integer value). Given: Bond energies of X X, X = X, Y = Y and X = Y are 940, 410, 500, and 602 kJ mol-1 respectively. Valence X: 3, Y: 2

Total enthalpy change for freezing of 1 mol of water at 10 C to ice at -10 C is (Given: fusH = x kJ/mol Cp[H2O(l)] = y J mol-1 K-1 Cp[H2O(s)] = z J mol-1 K-1)

1. -x-10y-10z
2. x-10y-10z
3. -10(100x+y+z)
4. 10(100x+y+z)

The hydration energies of K+ and Cl- are -x and -y kJ/mol respectively. If the lattice energy of KCl is -z kJ/mol, then the heat of solution of KCl is :

1. x + y + z
2. z - (x + y)
3. -z - (x + y)
4. x - y - z

The correct statement amongst the following is :

1. The standard state of a pure gas is the pure gas at a pressure of 1 bar and temperature 273 K.
2. f H 500 is zero for O2(g).
3. f H 298 is zero for O(g).
4. The term 'standard state' implies that the temperature is 0°C.

One mole of an ideal gas expands isothermally and reversibly from 10 dm3 to 20 dm3 at 300 K. U, q and work done in the process respectively are Given: R = 8.3 J K-1 mol-1 10 = 2.3 2 = 0.30 3 = 0.48

1. 0, 21.84 kJ, -1.726 J
2. 0, 21.84 kJ, 21.84 kJ
3. 0, 1.718 kJ, -1.718 kJ
4. 0, -17.18 kJ, 1.718 J

Let us consider a reversible reaction at temperature, T. In this reaction, both H and S were observed to have positive values. If the equilibrium temperature is Te, then the reaction becomes spontaneous at:

1. Te > T
2. T > Te
3. T = Te
4. Te = 5T

Consider the given data : (a) HCl(g) + 10H2O(l) HCl 10H2O; H = -69.01 kJ mol-1 (b) HCl(g) + 40H2O(l) HCl 40H2O; H = -72.79 kJ mol-1 Choose the correct statement :

1. The heat of dilution for the HCl (HCl 10H2O to HCl 40H2O) is 3.78 kJ mol-1.
2. Dissolution of gas in water is an endothermic process.
3. The heat of solution depends on the amount of solvent.
4. The heat of formation of HCl solution is represented by both (a) and (b).

Which of the following properties will change when system containing solution 1 will become solution 2 ? [figure]

1. Molar heat capacity
2. Concentration
3. Gibbs free energy
4. Density

Given : sub H [C (graphite)] = 710 kJ mol-1 C-H H = 414 kJ mol-1 H-H H = 436 kJ mol-1 C=C H = 611 kJ mol-1 The f H for CH2=CH2 is kJ mol-1 (nearest integer value)