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Chemistry

Thermodynamics

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For the given reaction : CO2(g) + H2(g) → CO(g) + H2O(g); ∆H = 40 kJ The ∆H is called;

Heat of formation of CO

Heat of combustion

Heat of reaction

Heat of hydrogenation of C = O bond

Given below are two statements: Statement I: First law of thermodynamics is able to predict the spontaneity of a chemical reaction. Statement II: For chemical reactions, heat absorbed at constant volume, is measured in a bomb calorimeter.

Statement I is correct but Statement II is incorrect.

Statement I is incorrect but Statement II is correct.

Both Statement I and Statement II are correct.

Both Statement I and Statement II are incorrect.

∆H and ∆S for a reaction are 4500 J mol–1 and 4.5 J K–1 mol–1 respectively. The reaction will be spontaneous;

Above 1000 K

At 900 K

Below 1000 K

Below 900 K

Enthalpy of combustion of carbon to CO2 is –393.52 kJ/mol. The heat released upon the formation of 11 g of CO2 from carbon and dioxygen is:

35.77 kJ

98.38 kJ

1574.08 kJ

393.52 kJ

Identify the correct statement regarding entropy.

At 0°C the entropy of a perfectly crystalline substance is taken to be zero.

At absolute zero of temperature, the entropy of a perfectly crystalline substance is +ve.

At absolute zero of temperature, the entropy of all crystalline substances is taken to be zero.

At absolute zero of temperature, the entropy of a perfectly crystalline substance is taken to be zero.

The value of Cp/Cv γ for a monoatomic gas is;

1.66

1.4

1.33

0.33

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

5.260 cal/(mol K)

0.526 cal/(mol K)

10.52 cal/(mol K)

21.04 cal/(mol K)

Which of the following reactions correctly indicates the process of atomization?

CH4(g) → CH3(g) + H(g)

CH4(g) → C(g) + 4H(g)

C(g) + O2(g) → CO2(g)

N2(g) + 3H2(g) → 2NH3(g)

100

In which of the following cases entropy decreases?

Solid changing to liquid

Expansion of a gas

Dissolution of crystals

Polymerisation

For which of the following species, standard molar enthalpy of formation at 298 K will not be zero?

H₂(g)

Cl₂(g)

Br₂(g)

I₂(s)

Heat required to raise the temperature of 1 mole of a substances by 1°C is called:

specific heat.

molar heat capacity.

water equivalent.

specific gravity.

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

q = 0, ∆T ≠ 0, w = 0

q ≠ 0, ∆T = 0, w = 0

q = 0, ∆T = 0, w = 0

The ∆H°f for CO2(g), CO(g) and H2O(g) are –393.5, –110.5 and –241.8 kJ mol–1 respectively the standard enthalpy change (in kJ) for the reaction CO2(g) + H2(g) → CO(g) + H2O(g) is:

524.1

41.2

–262.5

–41.2

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

+− − xyz

xyz + +

z (x y) − +

−− + z (x y)

When 1 mol of gas is heated at constant volume, temperature is raised from 298 to 308 K. Heat supplied to the gas is 500 J. Then which statement is correct?

q = w = 500 J, ∆U ≠ 0

q = ∆U = 500 J, w = 0

q = w = 500 J, ∆U = 0

∆U = 0, q = w = –500 J

When 229 J of energy is supplied as heat at constant pressure to 3 mol Ar(g), the temperature of the sample is increased by 2.55K. Calculate the molar heat capacity at constant volume;

30 kJ K–1 mol–1

30 J K–1 mol–1

21.7 J K–1 mol–1

21.7 kJ K–1 mol–1

The difference between enthalpy of reaction and change in internal energy at constant volume for the reaction given below at 25°C in kJ is: 2C6H6(l) + 15O2(g) → 12CO2(g) + 6H2O(l)

–7.43

+3.72

–3.72

+7.43

Formation of ozone takes place as O2(g) + O(g) → O3(g), ΔH = –107.2 kJ Assuming O = O bond energy as 498.8 kJ mol–1, the average bond energy of ozone is;

391.6 kJ mol–1

606.0 kJ mol–1

107.2 kJ mol–1

303 kJ mol–1

If the enthalpy change for the transition of liquid water to steam is 300 kJ mol–1 at 27°C, the entropy change for the process would be:

1000 JK–1 mol–1

10 JK–1 mol–1

1 JK–1 mol–1

0.1 JK–1 mol–1

The temperature of an ideal gas increases in an:

adiabatic expansion.

isothermal expansion.

adiabatic compression.

isothermal compression.

A gas expands from a volume of 1 m3 to a volume of 2 m3 against an external pressure of 105 N m–2. The work done by the gas will be;

105 kJ

102 kJ

102 J

103 J

In an adiabatic process which of the following is true :–

q = +w

–ΔU = –w

PΔV = 0

q = ΔU

An ideal gas expands in volume from 1 × 10–3 m3 to 1 × 10–2 m3 at 300 K against a constant pressure 1 × 10^5 Nm–2. The work done is;

–900 J

–900 kJ

270 kJ

900 kJ

A well stoppered thermos flask contains some ice cubes. This is an example of:

Closed system

Open system

Isolated system

Non-thermodynamic system

The heat of dissociation of benzene in isolated gaseous atoms is 5535 kJ/mol. The bond enthalpies of C–C, C=C and C–H bonds are 347.3, 615 and 416.2 kJ respectively. Magnitude of resonance energy of benzene is :

1.15 kJ

15.1 kJ

151 kJ

1511 kJ

Thermochemical reactions C(graphite) + 1/2 O2(g) → CO(g) ; ΔH = –110.5 kJ …(i) CO(g) + 1/2 O2(g) → CO2(g) ; ΔH = –283.2 kJ …(ii) From the above reaction, the heat of reaction for C(graphite)+O2(g) → CO2(g) will be

–393.7 kJ

+393.7 kJ

–172.7 kJ

+172.7 kJ

∆Hneutralisation is;

always positive.

always negative.

always zero.

positive or negative.

In thermodynamics, a process is called reversible when:

surroundings and system change into each other

there is no boundary between system and surroundings.

the surroundings are always in equilibrium with system.

the system changes into the surroundings spontaneously.

Which of the following relations are correct? A. ΔU = q + PV B. ΔG = ΔH – TΔS C. ΔS = qrev/T D. ΔH = ΔU + nRT

C and D only

B and C only

A and B only

B and D only

The incorrect option in the following table is:

– , + → spontaneous at all temperatures

+ , – → non-spontaneous at all temperatures

+ , + → spontaneous at low temperatures

– , – → spontaneous at low temperatures

Lattice and hydration energies of NaCl are +777.8 kJ mol–1 and –774.1kJ mol–1 respectively. Heat of solution of NaCl will be;

+1551.9 kJ mol–1

–15519 kJ mol–1

–37 kJ mol–1

+3.7 kJ mol–1

Hess’s law is used in the determination of

heat of reaction

heat of combustion

heat of formation

all of these.

Which of the following is not a state function?

Internal energy

Gibbs free energy

Heat

Enthalpy

a(iii), b(ii), c(iv), d(i)

a(iii), b(iv), c(ii), d(i)

a(i), b(iii), c(iv), d(ii)

a(i), b(iv), c(iii), d(ii)

Hess’s law states that;

The standard enthalpy of an overall reaction is the sum of the enthalpy changes in individual reactions at the same temperature.

Enthalpy of formation of a compound is same as the enthalpy of decomposition of the compound into constituent elements, but with opposite sign.

At constant temperature the pressure of a gas is inversely proportional to its volume.

The mass of a gas dissolved per litre of a solvent is proportional to the pressure of the gas in equilibrium with the solution.

Given below are two statements: Statement I: System and surroundings together constitute the universe. Statement II: The wall that separates the system from the surroundings is called boundary.

Statement I is correct but Statement II is incorrect.

Statement I is incorrect but Statement II is correct.

Both Statement I and Statement II are correct.

Both Statement I and Statement II are incorrect.

The property, which can be classified as an intensive property, is;

volume

mass

heat capacity

temperature.

Given below are two statements: Statement I: A process or change is said to be reversible, if a change is brought out in such a way that the process could be reversed by an infinitesimal change. Statement II: A reversible process proceeds infinitely slowly by a series of equilibrium states such that system and the surroundings are always in near equilibrium with each other.

Statement I is correct but Statement II is incorrect.

Statement I is incorrect but Statement II is correct.

Both Statement I and Statement II are correct.

Both Statement I and Statement II are incorrect.

Calculate the work done when 1 mole of an ideal gas is compressed reversibly from 1.0 bar to 4.00 bar at constant temperature of 300 K.

3.46 kJ

–8.20 kJ

18.02 kJ

–14.01 kJ

∆U is always positive when;

system absorbs heat and work is done on it

system emits heat and work is done by it.

system emits heat and no work is done on it.

system absorbs heat and work is done by it.

Given below are two statements: Statement I: If work is done on the system then work is positive. Statement II: If the work is done by the system then work is negative.

Statement I is correct but Statement II is incorrect.

Statement I is incorrect but Statement II is correct.

Both Statement I and Statement II are correct.

Both Statement I and Statement II are incorrect.

In the combustion of 0.4 g of CH4, 0.25 kCal. of heat is liberated. The heat of combustion of CH4 is

–20 kCal

–10 kCal

–2.5 kCal

–5 kCal

Calculate entropy change when 5 moles of an ideal gas expands reversibly and isothermally from an initial volume of 5 litre to 50 litre at 27°C.

190.15 J K–1

95.74 J K–1

87.25 J K–1

90.13 J K–1

Consider the reaction, 2X(s) + Y(g) → 2Z(g) + 700 kJ The signs of ΔH, ΔS and ΔG respectively are;

∆H = –ve, ∆S = –ve, ∆G = –ve

∆H = –ve, ∆S = +ve, ∆G = +ve

∆H = –ve, ∆S = –ve, ∆G = +ve

∆H = –ve, ∆S = +ve, ∆G = –ve

Heat evolved in the reaction H2 + Cl2 → 2HCl is 182 kJ. Bond energies of H—H and Cl—Cl are 430 and 242 kJ mol–1 respectively. The H–Cl bond energy is :

245 kJ mol–1

427 kJ mol–1

336 kJ mol–1

154 kJ mol–1

Two moles of an ideal gas are allowed to expand reversibly and isothermally at 300 K from a pressure of 1 atm to a pressure of 0.1 atm. The change in Gibbs free energy is:

–11.488 J

+11.488 J

–11.488 kJ

zero.

X = 2Y

X = 3Y

X = 4Y

X = Y/2