Thermodynamics

At a certain temperature, T(K), during a process, 500 J is absorbed by the system and work of 200 J is done by the system. Then change in internal energy of the system is :

1. 700 J
2. 400 J
3. 300 J
4. 500 J

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

Two moles of an ideal gas undergo free expansion from 10 L to 100 L at 300 K. The values of Ssystem and Ssurroundings are (R is universal gas constant)

1. Ssystem = 4.606 R; Ssurroundings = 0
2. Ssystem = 0; Ssurroundings = 0
3. Ssystem = 4.606 R; Ssurroundings = -4.606 R
4. Ssystem = 0; Ssurroundings = 4.606 R

Consider the reversible processes for 1.0 mol of an ideal gas as shown in the figure. [figure] w1, w2, w3 and w4 represent work done (in calories) in the processes 1, 2, 3 and 4, respectively; U2 and U4 are changes in the internal energy for the processes 2 and 4, respectively. [use R = 2 cal K-1 mol-1] The correct option is

1. w1 + w2 + w3 + w4 = 0
2. w1 + w3 = -2T1 V2V1 - 2T2 V4V3
3. w2 + w4 = U2 - U4
4. w1 + w2 = 2T1 V2V1

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

The standard heat of formation, in kcal/mol of Ba2+ is : [Given : standard heat of formation of SO42- ion (aq) = -216 kcal/mol, standard heat of crystallisation of BaSO4(s) = -4.5 kcal/mol, standard heat of formation of BaSO4(s) = -349 kcal/mol]

1. +133.0
2. +220.5
3. -128.5
4. -133.0

C(s) + 2H2(g) CH4(g); H = -74.8 kJ mol-1. Which of the following diagrams gives an accurate representation of the above reaction? [R reactants; P products]

1. [figure]
2. [figure]
3. [figure]
4. [figure]

In which of the following processes entropy increases? Choose the correct answer from the options given below:

1. A and C
2. A, B and D
3. A, C and D
4. C and D

The work done during reversible isothermal expansion of one mole of hydrogen gas at 25 from pressure of 20 atmosphere to 10 atmosphere is (Given R = 2.0 cal K-1 mol-1)

1. 0 calorie
2. -413.14 calories
3. 413.14 calories
4. 100 calories

Choose the correct statement for the work done in the expansion and heat absorbed or released when 5 litres of an ideal gas at 10 atmospheric pressure isothermally expands into vacuum until volume is 15 litres :

1. Both the heat and work done will be greater than zero
2. Heat absorbed will be less than zero and work done will be positive
3. Work done will be zero and heat will also be zero
4. Work done will be greater than zero and heat will remain zero

For an endothermic reaction: Choose the correct answer from the options given below:

1. B and D
2. C and D
3. A and B
4. A and C

For the following reaction at 300 K A2(g) + 3B2(g) 2AB3(g) the enthalpy change is +15 kJ, then the internal energy change is :

1. 19988.4 J
2. 200 J
3. 1999 J
4. 1.9988 kJ

Which amongst the following options is the correct relation between change in enthalpy and change in internal energy?

1. H = U + ng RT
2. H - U = - n RT
3. H + U = n R
4. H = U - ng RT

Which of the following p-V curve represents maximum work done?

1. [figure]
2. [figure]
3. [figure]
4. [figure]

One mole of an ideal gas at 300 K is expanded isothermally from 1 L to 10 L volume. U for this process is : (Use R = 8.314 J K-1 mol-1)

1. 0 J
2. 1260 J
3. 2520 J
4. 5040 J

Which one among the following is the correct option for right relationship between CP and CV for one mole of ideal gas?

1. CV = RCP
2. CP + CV = R
3. CP - CV = R
4. CP = RCV

For irreversible expansion of an ideal gas under isothermal condition, the correct option is :

1. U 0, Stotal = 0
2. U = 0, Stotal = 0
3. U 0, Stotal 0
4. U = 0, Stotal 0

For the reaction, 2Cl(g) Cl2(g), the correct option is :

1. r H > 0 and r S < 0
2. r H < 0 and r S > 0
3. r H < 0 and r S < 0
4. r H > 0 and r S > 0

The correct option for free expansion of an ideal gas under adiabatic condition is :

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

In which case change in entropy is negative?

1. Sublimation of solid to gas
2. 2H(g) H2(g)
3. Evaporation of water
4. Expansion of a gas at constant temperature

Under isothermal condition, a gas at 300 K expands from 0.1 L to 0.25 L against a constant external pressure of 2 bar. The work done by the gas is [Given that 1 L bar = 100 J]

1. 25 J
2. 30 J
3. −30 J
4. 5 kJ

The bond dissociation energies of X2, Y2 and XY are in the ratio of 1 : 0.5 : 1. H for the formation of XY is -200 kJ mol-1. The bond dissociation energy of X2 will be

1. 800 kJ mol-1
2. 200 kJ mol-1
3. 400 kJ mol-1
4. 100 kJ mol-1

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

A gas is allowed to expand in a well insulated container against a constant external pressure of 2.5 atm from an initial volume of 2.50 L to a final volume of 4.50 L. The change in internal energy U of the gas in joules will be

1. -500 J
2. -505 J
3. +505 J
4. 1136.25 J

For a sample of perfect gas when its pressure is changed isothermally from pi to pf, the entropy change is given by

1. S = nR ( pfpi )
2. S = nR ( pipf )
3. S = nRT ( pfpi )
4. S = RT ( pipf )

The heat of combustion of carbon to CO2 is -393.5 kJ/mol. The heat released upon formation of 35.2 g of CO2 from carbon and oxygen gas is

1. +315 kJ
2. -630 kJ
3. -3.15 kJ
4. -315 kJ

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

When 5 litres of a gas mixture of methane and propane is perfectly combusted at 0 and 1 atmosphere, 16 litres of oxygen at the same temperature and pressure is consumed. The amount of heat released from this combustion in kJ ( Hcomb.(CH4) = 890 kJ mol-1, Hcomb.(C3H8) = 2220 kJ mol-1) is

1. 38
2. 317
3. 477
4. 32

Three thermochemical equations are given below (i) C(graphite) + O2(g) CO2(g); r H = x kJ mol-1 (ii) C(graphite) + 12O2(g) CO(g); r H = y kJ mol-1 (iii) CO(g) + 12O2(g) CO2(g); r H = z kJ mol-1 Based on the above equations, find out which of the relationship given below is correct.

1. z = x + y
2. x = y + z
3. y = 2z − x
4. x = y − z