1. Select the most apropriate option.

i. The correct thermodynamic
conditions for the spontaneous
reaction at all temperatures are
a. ΔH < 0 and ΔS > 0
b. ΔH > 0 and ΔS < 0
c. ΔH < 0 and ΔS < 0
d. ΔH < 0 and ΔS = 0

ii. A gas is allowed to expand in a well insulated container against a constant external pressure of 2.5 bar from an initial volume of 2.5 L to a final volume of 4.5 L. The change in internal energy, ΔU of the gas will be

a. -500 J

b. + 500 J
c. -1013 J

d. + 1013 J

iii. In which of the following, entropy of the system decreases?

a. Crystallization of liquid into solid
b. Temperature of crystalline solid is increased from 0 K to 115 K
c. H2(g)→ 2H(g)

d. 2 NaHCO3(s) →Na2CO3(s) + CO2(g) + H2O(g)

iv. The enthalpy of formation for all elements in their standard states is
a. unity
b. zero
c. less than zero
d. different elements

v. Which of the following reactions is exothermic?

a. H2(g) →2H(g)
b. C(s)→ C(g)
c. 2 Cl(g) →Cl2(g)
d. H2O(s)→ H2O(l).

vi. 6.24 g of ethanol are vaporized by supplying 5.89 kJ of heat. Enthalpy of vaporization of ethanol will be
a. 43.4 kJ mol-1
b. 60.2 kJ mol-1
c. 38.9 kJ mol-1
d. 20.4 kJ mol-1

vii. If the standard enthalpy of formation of methanol is -238.9 kJ mol-1 then entropy change of the surroundings
will be
a. -801.7 J K-1

b. 801.7 J K-1
c. 0.8017 J K-1

d. -0.8017 J K-1

viii. Which of the following are not state functions?
1. Q + W            2. Q                3. W                4. H-TS

a. 1,2 and 3

b. 2 and 3
c. 1 and 4

d. 2,3 and 4

ix. For vaporization of water at 1 bar, ΔH = 40.63 kJ mol-1 and ΔS = 108.8 J K-1 mol-1. At what temperature, ΔG = 0 ?
a. 273.4 K

b. 393.4 K
c. 373.4 K

d. 293.4 K

x. Bond enthalpies of H-H, Cl-Cl and H-Cl bonds are 434 kJ mol-1, 242 kJ mol-1 and 431 kJ mol-1, respectively. Enthalpy of formation of HCl is
a. 245 kJ mol-1

b. -93 kJmol-1
c. -245 kJ mol-1

d. 93 kJ mol-1

2. Answer the following in one or two sentences.

i. Comment on the statement: no workis involved in an expansion of gas in vacuum

ii. State the first law of thermodynamics

iii. What is enthalpy of fusion?

iv. What is standard state of a substance?.

v. State whether ΔS is positive, negative or zero for the reaction 2H(g) →H2(g). Explain.

vi. State second law of thermodynamics in terms of entropy.

vii. If the enthalpy change of a reaction is ΔH how will you calculate entropy of surroundings?

viii. Comment on spontaneity of reactions for which ΔH is positive and ΔS is negative.

3. Answer in brief.

i. Obtain the relationship between ΔG0 of a reaction and the equilibrium constant.

ii. What is entropy? Give its units.

iii. How will you calculate reaction enthalpy from data on bond enthalpies?

iv. What is the standard enthalpy of combustion ? Give an example.

v. What is the enthalpy of atomization?
Give an example.

vi. Obtain the expression for work done in chemical reaction.

vii. Derive the expression for PV work

viii. What are intensive properties?
Explain why density is intensive property.

ix. How much heat is evolved when 12 g of CO reacts with NO2 ? The reaction is : 4 CO(g) + 2 NO2(g) → 4 CO2(g) + N2(g), ΔrH0 = -1200 kJ

4. Answer the following questions.

i. Derive the expression for the maximum work.

ii. Obtain the relatioship between ΔH and ΔU for gas phase reactions.

iii. State Hess’s law of constant heat summation. Illustrate with an example. State its applications.

iv. Although ΔS for the formation of two moles of water from H2 and O2 is -327JK-1, it is spontaneous. Explain. (Given ΔH for the reaction is -572 kJ).

v. Obtain the relation between ΔG and ΔStotal Comment on spontaneity of the reaction.

vi. One mole of an ideal gas is compressed from 500 cm3 against a constant external pressure of 1.2 × 105 Pa. The work involved in the process is 36.0 J. Calculate the final volume. (200 cm3)

vii. Calculate the maximum work when 24 g of O2 are expanded isothermally and reversibly from the pressure of 1.6 bar to 1 bar at 298 K.

viii. Calculate the work done in the decomposition of 132 g of NH4NO3 at  100 0C. NH4NO3(s)→ N2O(g) + 2 H2O(g) State whether work is done on the system or by the system.
ix. Calculate standard enthalpy of reaction, Fe2O3(s) + 3CO(g)→ 2 Fe(s) + 3CO2(g), from the following data. ΔfH0(Fe2O3) = -824 kJ/mol, ΔfH0(CO) = -110 kJ/mol, ΔfH0(CO2) = -393 kJ/mol

x. For a certain reaction ΔH0 =219 kJ and ΔS0 = -21 J/K. Determine whether the reaction is spontaneous or nonspontaneous.

xi. Determine whether the following reaction is spontaneous under standard state conditions. 2 H2O(l) + O2(g)→ 2H2O2(l) if ΔH0 = 196 kJ, ΔS0 = -126 J/K Does it have a cross-over temperature? (Nonspontaneous, No)
xii. Calculate ΔU at 298 K for the reaction, C2H4(g) + HCl(g)→ C2H5Cl(g), ΔH = -72.3 kJ How much PV work is done? Ans. : (-69.8 kJ, 2.48 kJ)

xiii. Calculate the work done during synthesis of NH3 in which volume changes from 8.0 dm3 to 4.0 dm3 at a constant external pressure of 43 bar. In what direction the
work energy flows?
Ans. : (17.2 kJ, work energy flows into system)

xiv. Calculate the amount of work done in the (a) oxidation of 1 mole HCl(g) at 200 0C according to reaction. 4HCl(g) + O2(g) →2 Cl2(g) + 2 H2O(g) (b) decomposition of one mole of NO at 300 0C for the reaction 2 NO(g)→ N2(g) + O2 Ans. : (a = + 983 kJ ; b = 0 kJ)
xv. When 6.0 g of O2 reacts with CIF as per 2Cl F(g) + O2(g) →Cl2O(g) + OF2(g) The enthalpy change is 38.55 kJ. What is standard enthalpy of the reaction ? (ΔrH0 = 205.6 kJ)

xvi. Calculate the standard enthalpy of formation of CH3OH(l) from the following data
i.CH3OH(l)+ 32O2(g)  →CO2(g)+ 2H2O(l), ΔH0 = -726 kJ mol-1


ii. C (Graphite) + O2(g) →CO2(g), ΔcH0 = -393 kJ mol-1


iii. H2(g) + 12 O2(g)→ H2O(l), ΔfH0 = -286 kJ mol-1

Ans. : (- 239 kJ mol-1)

xvii. Calculate ΔH0 for the following reaction at 298 K H2B4O7(s) + H2O(l) 4HBO2 (aq) i. 2H3BO3(aq)→ B2O3(s) + 3H2O(l), ΔH0 = 14.4 kJ mol-1 ii. H3BO3(aq)→ HBO2(aq) + H2O,(l) ΔH0 = -0.02 kJ mol-1 iii. H2B4O7(s)→ 2P2O3(s) + H2O(l), ΔH0 =17.3 kJ mol-1 Ans. : (- 11.58 kJ)

xviii. Calculate the total heat required (a) to melt 180 g of ice at 0 0C, (b) heat it to 100 0C and then (c) vapourise it at that
temperature. Given ΔfusH0(ice) = 6.01 kJ mol-1 at 0 0C, ΔvapH0(H2O) = 40.7 kJ mol-1 at 100 0C specific heat of water is 4.18 J g-1 K-1 Ans. : (542.3 kJ)

xix. The enthalpy change for the reaction, C2H4(g) + H2(g) →C2H6(g) is -620 J when 100 ml of ethylene and 100 mL of H2 react at 1 bar pressure. Calculate the pressure volume type of work and ΔU for the reaction. Ans.: (W = +10.13 J; ΔU = -609.9 J)

xx. Calculate the work done and comment on whether work is done on or by the system for the decomposition of 2 moles of NH4NO3 at 100 0C NH4NO3(s) N2O(g) + 2H2O(g)
Ans. (-18.61 kJ, work is done by the system)