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Chemistry

Thermodynamics

174 questions · Click an option and press Check Answer to reveal the result

For the process : NH₃ (g) + HCl (g) → NH₄Cl (s) ; Which one is correct ?

ΔH > 0 ; ΔS > 0

ΔH < 0 ; ΔS > 0

ΔH > 0 ; ΔS < 0

ΔH < 0 ; ΔS < 0

Enthalpy of formation of compound is -

always positive

always negative

can be either negative or zero

can be positive or negative

Heats of combustion of CH₄, C₂H₆ , C₃H₈ , C₈H₁₈ in K. cals mole⁻¹ as − 210.8, − 368.4, − 526.3, −1302.7 respectively. Decide which is better rocket fuel -

C₈H₁₈

CH₄

C₃H₈

C₂H₆

For a reversible process -

Δ Ssys. + Δ Ssurr. > 0

ΔG > 0

ΔSsys. = − ΔSsurr.

ΔG < 0

Given that CO(g) + O₂(g) ⟶ CO₂(g); ΔH° = − x kJ which of the following is correct –

ΔH°comb of C = − x kJ mol⁻¹

ΔHf° of CO₂ = − x kJ mol⁻¹

ΔHcomb. of CO(g) = − x kJ mol⁻¹

ΔHf of CO = +x kJ mol⁻¹

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.

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

q = 0, ∆T < 0, w ≠ 0

For the process - CO₂(s) → CO₂(g)

Both ΔH and ΔS are positive

ΔH is negative and ΔS is positive

ΔH is positive and ΔS is negative

Both ΔH and ΔS are negative

Free energy change of reversible reaction at equilibrium is -

Infinite

Zero

Positive

Negative

The total entropy change for a system and its surroundings increases, if the process is

Reversible

Irreversible

Exothermic

Endothermic

The enthalpy of the reaction H₂O₂(l) → H₂O(l) + 1/2 O₂(g) − 23.5 kcal mol⁻¹ and the enthalpy of formation of H₂O(l) is − 68.3 kcal mol⁻¹. The enthalpy of formation of H₂O₂(l) is -

−44.8 kcal mol⁻¹

44.8 kcal mol⁻¹

−91.8 kcal mol⁻¹

91.8 kcal mol⁻¹

Heat of neutralisation of HF is -

57.32 kJ

> 57.32 kJ

< 57.32 kJ

None

For a reversible reaction at equilibrium, ΔG is -

positive

negative

zero

may be positive or negative

Bond energy of a substance -

Is always negative

Is always positive

Either positive or negative

Depends upon the physical state of the system

The heat of combustion of ethylene C₂H₄(g) is − 1420 kJ/mole. The volume of C₂H₄ at NTP that would evolve 355 kJ on combustion is -

2.8 lit

8.4 lit

5.6 lit

11.2 lit

In the combustion of 4 g of CH₄, 2.5 kcal of heat is liberated. The heat of combustion of CH₄ is -

20 kcal

10 kcal

2.5 kcal

5 kcal

The enthalpy of formation of ammonia is −46.0 kJ mol⁻¹. The enthalpy for the reaction 2N₂(g) + 6H₂(g) → 4NH₃(g) is equal to -

−46.0 kJ

46.0 kJ

184.0 kJ

−184.0 kJ

HA + OH⁻ → H₂O + A⁻ + q₁ kJ H⁺ + OH⁻ → H₂O + q₂ kJ The enthalpy of dissociation of HA is

(q₁ + q₂)

(q₁ − q₂)

(q₂ − q₁)

−(q₁ + q₂)

The heats of neutralisation of four acids a, b, c and d when neutralised against a common strong base are 13.7, 9.4, 11.2 and 12.4 kcal respectively. The weakest acid among these is

The heat change accompanying the reaction 2H₂ (g) + O₂ (g) → 2H₂ O (ℓ) ; Δ H = −136 kcal is called -

heat of combustion of hydrogen

heat of reaction

heat of formation of water

none of these

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 reaction at constant volume (ΔE) and that at constant pressure (ΔH) are related as-

ΔE = ΔH + ΔnRT

ΔH = ΔE − ΔnRT

ΔH = ΔE + ΔnRT

ΔH = ΔE + nRT

The heat of combustion of ethanol determined in a bomb calorimeter is −670.48 K. cals mol⁻¹ at 25°C. What is ΔE at 25°C for the reaction -

−335.24 K. cals

−669.28 K.cals

−670.48 K.cals

+ 670.48 K.cals

Heat evolved in the reaction H₂ + Cl₂ → 2HCl is 182 KJ. Bond energies H − H =430 KJ/mole, Cl − Cl = 242 KJ/mole. The H − Cl bond energy is-

763 kJ mole⁻¹

427 kJ mole⁻¹

336 kJ mole⁻¹

154 kJ mole⁻¹

From the following data, the heat of formation of Ca(OH)₂(s) at 18°C is ______ kcal:

−98.69

−235.43

194.91

98.69

If the enthalpy of vapourisation of water is 186.5 J mol⁻¹, the entropy of its vapourisation will be -

0.5 JK⁻¹ mol⁻¹

1.0 JK⁻¹ mol⁻¹

1.5 JK⁻¹ mol⁻¹

2.0 JK⁻¹ mol⁻¹

The solubility of NaCl in water at 25° C is about 6 moles per litre. Suppose you add 1 mole of NaCl to a litre of water. For the reaction, NaCl + H₂O → Salt solution -

ΔG > 0, ΔS > 0

ΔG < 0, ΔS > 0

ΔG > 0, ΔS < 0

ΔG < 0, ΔS < 0

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

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.

Which of the following state function is not zero at standard state -

Enthalpy

Entropy

Free energy

Entropy and enthalpy

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

Which among the following is not a state function -

Internal energy

Free energy

Work

Enthalpy

When an egg is hard boiled, there is -

Increase in disorder

Decrease in disorder

No change in disorder

ΔG is negative

Which one of the following is correct -

−ΔG = ΔH − TΔS

ΔH = ΔG − T Δ S

ΔS = 1/T [ΔG − Δ H ]

ΔS = 1/T [ΔH − ΔG]

For which of the following substances, the standard heat of formation is zero :

C(graphite)

C(diamond)

CO₂

O₃

In any natural process -

The entropy of the universe remains constant

The entropy of universe tends towards maximum.

The entropy of universe tends towards minimum.

Any of the above can happen

The enthalpy of formation for C₂H₄(g), CO₂(g) and H₂O(l) at 25°C and 1 atm pressure be 52, −394 and −286 kJ mol⁻¹ respectively. The enthalpy of combustion of C₂H₄(g) will be -

+ 1412 kJ mol⁻¹

− 1412 kJ mol⁻¹

+ 141.2 kJ mol⁻¹

− 141.2 kJ mol⁻¹

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.

Enthalpy of neutralisation of NaOH with H₂SO₄ is − 57.3 KJ mole⁻¹ and − 55.2 KJ mol⁻¹ with ethanoic acid. Which of the following is the best explanation of this difference -

Ethanoic acid is a weak acid and thus requires less NaOH for neutralisation

Ethanoic acid is only partly ionised, neutralisation is therefore incomplete

Ethanoic acid is monobasic while H₂SO₄ is di-basic

Some heat is used to ionized ethanoic acid completely

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

Given that ΔHcomb. of cyclopropane is − 4000 kJ mol⁻¹. The amount of cyclopropane that needs to be burnt in oxygen for producing 2 × 10⁵ kJ of heat is -

20 kg

2.1 kg

21 g

210 mg

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

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

The occurrence of reaction is impossible if

ΔH is +ve ; ΔS is +ve

ΔH is −ve ; ΔS is −ve

ΔH is −ve ; ΔS is +ve

ΔH is +ve ; ΔS is −ve

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

q = 0, ΔT < 0, w ≠ 0

q = 0, ΔT ≠ 0, w = 0

q ≠ 0, ΔT = 0, w = 0

q = 0, ΔT = 0, w = 0

One litre-atmosphere is approximately equal to-

19.2 J

101 J

8.31 J

831 J

For the process 2F (g) → F₂(g), the sign of ΔH and ΔS respectively are -

+, −

+, +

−, −

−, +

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.

The work done by the system in a cyclic process involving one mole of an ideal monoatomic gas is −50 kJ/cycle. The heat absorbed by the system per cycle is -

Zero

50 kJ

− 50 kJ

250 kJ

Difference between ΔH and ΔE for the combustion of liquid benzene at 27°C is -

7.48 kJ

3.74 kJ

14.86 kJ

5.73 kJ

A gas absorbs 200J of heat and expands against the external pressure of 1.5 atm from a volume of 0.5 litre to 1.0 litre, Calculate the change in internal energy

124 J

224 J

114 J

154 J

For the reversible vapourisation of water at 100° C and 1 atmospheric pressure. ΔG is equal to?

ΔH

ΔS

Zero

ΔH/T

In which of the following cases entropy decreases?

Solid changing to liquid

Expansion of a gas

Dissolution of crystals

Polymerisation

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

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

1.66

1.4

1.33

0.33

Under the same conditions how many ml of 1 M KOH and 0.5 M H₂SO₄ solutions respectively when mixed for a total volume of 100 ml produce the highest rise in temperature -

67, 33

36, 67

40, 60

50, 50

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 heat of neutralisation is constant when dilute solution of -

strong acid and strong base react

strong acid and weak base react

strong base and weak acid react

in all the cases

A gas is allowed to expand at constant pressure from a volume of 1.0 litre to 10.0 litre against an external pressure of 0.50 atm. If the gas absorbs 250 J of heat from the surroundings, what are the values of q, w and ΔE ? (Given 1 L atm = 101 J)

250 J, − 455 J, − 205 J

−250 J, − 455 J, − 710 J

250 J, 455 J, 710 J

−250 J, 455 J, 205 J

One mole of an ideal gas at 300 K is expanded isothermally from an initial volume of 1 litre to 10 litres. The ΔE for this process is (R = 2 cal mol⁻¹ K⁻¹) -

163.7 cal

zero

138.1 cal

9 lit atm.

F₂C = CF−CF = CF₂ ⟶ cyclic product For this reaction (ring closure), ΔH = −49 kJ mol⁻¹, ΔS = −40.2 J K⁻¹ mol⁻¹. Upto what temperature is the forward reaction spontaneous ?

1492°C

1219°C

946°C

1080°C

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

ΔS° and ΔH° for combustion of methane are 186 JK⁻¹ and − 74.8 kJ mol⁻¹ respectively. The value of ΔU° for the process would be -

unpredictable

(74.8 − R) JK⁻¹

74.78 kJ

(596 R − 74.8) kJ

For the spontaneity of a reaction , which is true-

ΔG = +ve, ΔH = + ve

ΔH = +ve, ΔS = - ve

ΔG = +ve, ΔH = - ve

ΔH = - ve, ΔS = + 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

For a reaction A (g) + 3 B (g) → 2C(g) ; Δ H° = −24 kJ The value of ΔG° is - 9 kJ. The standard entropy change of reaction is :

5 JK⁻¹

−50 JK⁻¹

500 JK⁻¹

0.5 JK⁻¹

An exothermic reaction has a large positive entropy change. The reaction will be -

Possible → Spontaneous at all temperatures

Possible → Spontaneous at low temperatures only

Impossible → Non-spontaneous at all temperatures

Possible → Spontaneous at high temperatures only

The enthalpy of combustion at 25°C of H₂, cyclohexane (C₆H₁₂) and cyclohexene (C₆H₁₀) are − 241, −3920 and −3800 kJ/mol respectively. The heat of hydrogenation of cyclohexene is -

−121 kJ/mol

+121 kJ/mol

−242 kJ/mol

+242 kJ/mol

For hypothetical reaction - A(g) + B(g) → C(g) + D(g) Which of the following statements is correct -

ΔH = ΔE

ΔH > ΔE

ΔH < ΔE

unpredictable

Given : Heat of ionization of two acids : ΔH° (HCN) = 45.2 kJ mol⁻¹ ΔH° (CH₃COOH) = 2.1 kJ mol⁻¹ which relationship for the two acids is true –

pKa (HCN) = pKa (CH₃COOH)

pKa (HCN) > pKa(CH₃COOH)

pKa (HCN) < pKa(CH₃COOH)

pKa(HCN) = 45.2/2.1 pKa(CH₃COOH)

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

Ammonium nitrate can decompose with explosion: NH₄NO₃(s) → N₂O(g) + 2H₂O ; ΔH = −37.0 kJ mol⁻¹ Calculate the heat produced when 2.50 g NH₄NO₃ decomposes -

1.06 kJ

0.96 kJ

1.16 kJ

1.26 kJ

The least random state of H₂O is -

Ice

liquid water

Steam

Randomness is same in all

The heat change for the reaction C (s) + 2S (s) → CS₂(ℓ) is called -

Heat of transition

Heat of fusion

Heat of formation

Heat of combustion.

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.

Under certain conditions, the value of ΔG for a hypothetical reaction, X + Y ⟶ Z is greater than zero, then –

The reaction has tendency to proceed towards Z

The reaction has attained equilibrium

increase in temperature increases the yield of product Z

X and Y predominate in the final mixture

For the chemical reaction A + B ⟶ P + Q two paths are given in the diagram. Which of the following relationship is correct –

ΔH₁ + ΔH₂ = ΔH₃ + ΔH₄

ΔH₁ + ΔH₂ = ΔH₃ − ΔH₄

ΔH₃ − ΔH₁ = ΔH₄ − ΔH₂

ΔH₁ − ΔH₂ = ΔH₃ + ΔH₄

The latent heats of fusion in J g⁻¹ of five substances a (mol.mass = 18) ; b (mol. mass = 20) ; c (mol. mass = 30), d (mol. mass = 60) and e (mol. mass = 30) are respectively 80, 45, 90, 45, 45. Which of following pair has same value of ΔHfusion-

a,c

b,e

d,e

c,d

The work done by the system in the conversion of 1 mol of water at 100° C and 760 torr to steam is 3.1 KJ. Calculate Δ E for the conversion (Latent heat of vaporisation of water is 40.65 kJ. mol⁻¹)

43.75 KJ

101.35 KJ

37.55 KJ

− 40.65 KJ

A hypothetical reaction , A → 2B, proceeds through following sequence of steps - A → C; ΔH = q₁ C → D; ΔH = q₂ 1/2 D → B; ΔH = q₃ The heat of reaction is :

q₁ − q₂ + 2q₃

q₁ + q₂ − 2q₃

q₁ + q₂ + 2q₃

q₁ + 2q₂ − 2q₃

The temperature of an ideal gas increases in an:

adiabatic expansion.

isothermal expansion.

adiabatic compression.

isothermal compression.

The Bond-energies of C ≡ C, C—H, H—H and C = C are 198, 98, 103, 145 kcal respectively. The enthalpy change of the reaction HC ≡ CH + H₂ ⟶ C₂H₄ is -

− 152 kcal

96 kcal

48 kcal

− 40 kcal

Which of the following has highest entropy -

Water

Graphite

Mercury

Hydrogen

How much heat is liberated when 100 mL of 0.1 M NaOH are completely neutralised by 100 mL of 0.1 M HCl -

−57 kJ

−0.57 kJ

−5.7 kJ

−0.05 kJ

Standard enthalpies of formation of O₃, CO₂, NH₃ and HI are 142.2, −393.2, −46.2 and +25.9 kJ mol⁻¹ respectively. The order of their increasing stabilities will be -

O₃, CO₂, NH₃, HI

CO₂, NH₃, HI, O₃

O₃, HI, NH₃, CO₂

NH₃, HI, CO₂, O₃

Which of the following process/es proceed towards more disordered state ? (i) Stretching the rubber band (ii) Sublimation of dry ice (iii) Crystallisation of salt from solution (iv) dissolution of sugar in water

i, iv

i, iii

iii, iv

ii, iv

The product of combustion of an aliphatic thiol (R SH) at 298 K are :

CO₂(g), H₂O(g) and SO₂(g)

CO₂(g), H₂O(l) and SO₂(g)

CO₂(l), H₂O(l) and SO₂(g)

CO₂(g), H₂O(l) and SO₂(l)

The value of ΔHsol of BaCl₂(s) and BaCl₂·2H₂O(s) are −a kJ and b kJ respectively. The value of ΔHHydration of BaCl₂(s) is-

b − a

a + b

−a − b

a − b

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

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

Consider the following reactions at 1000°C - I. Zn(s) + 1/2 O₂(g) → ZnO(s); ΔG° = −360 kJ mol⁻¹ II. C(graphite) + 1/2 O₂(g) → CO(g); ΔG° = −460 kJ mol⁻¹ Choose the correct statement at 1000°C :

zinc can be oxidised by carbon monoxide

ZnO can be reduced by graphite

both (I) and (II) are true

both (I) and (II) are false

If for H₂ (g) + 1/2 O₂ (g) → H₂O (g); Δ H₁ is enthalpy of reaction and for H₂(g) + 1/2 O₂ (g) → H₂O (ℓ) Δ H₂ is enthalpy of reaction. Then magnitude of-

Δ H₁ > Δ H₂

Δ H₁ = Δ H₂

Δ H₁ < Δ H₂

Δ H₁ + Δ H₂ = 0.

The enthalpies of formation of N₂O and NO are 82 and 90 kJ mol⁻¹, respectively. The enthalpy of the reaction is : 2N₂O(g) + O₂(g) → 4NO(g) would be -

− 16 KJ

196 KJ

8 KJ

88 KJ

Which of the following is not a state function?

Internal energy

Gibbs free energy

Heat

Enthalpy

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

The value of ΔHf° of U₃O₈ is −853.5 KJ mol⁻¹. Also ΔH° for the reaction 3 UO₂ + O₂ ⟶ U₃O₈, is −76.00 KJ. The value of ΔHf° of UO₂ is approx –

−259.17 KJ

−310.17 KJ

+ 259.17 KJ

930.51 KJ

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

For the reaction between CO₂ and graphite CO₂(g) + C(s) → 2CO(g) ΔH = + 170.0 kJ and ΔS = 170 JK⁻¹. The reaction is spontaneous at -

298 K

500 K

900 K

1200 K

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.

100

Equal volumes of 1 M HCl and 1 M H₂SO₄ are neutralized by 1 M NaOH solution and x and y kJ/equivalent of heat are liberated respectively. Which of the following relations is correct ?

x = 2y

x = 3y

x = 4y

x = 1/2y

101

Select the correct order in the following:

1 erg > 1 joule > 1 cal

1 cal > 1 joule > 1 erg

1 erg > 1 cal > 1 joule

1 joule > 1 cal > 1 erg

102

The value of log₁₀K for a reaction A⇌B is: (Given, Δ_rH°_298K = −54.07 kJ mol⁻¹, Δ_rS°_298K = 10 JK⁻¹ mol⁻¹ and R = 8.314 JK⁻¹ mol⁻¹ ; 2.303 × 8.314 × 298 = 5705)

100

103

Two moles of an ideal monoatomic gas are allowed to expand adiabatically and reversibly from 300 K to 200 K. The work done in the process is (Cv = 12.5 J/K/mol) -

− 12.5 kJ

− 2.5 kJ

− 6.25 kJ

500 kJ

104

According to the diagram given below, the value of ΔH for conversion of A to B is -

− 40

+ 40

−120

+ 120

105

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)

106

The lattice enthalpy and hydration enthalpy of four compounds are given below – Compound Lattice enthalpy Hydration enthalpy P +780 −920 Q +1012 −812 R +828 −878 S +632 −600 The pair of compounds which is soluble in water is -

P and Q

Q and R

R and S

P and R

107

Which of the following process involves decrease in the entropy of system -

Br₂(ℓ) ⟶ Br₂(g)

Elongating the rubber band

N₂(g) [50°C] ⟶ N₂(g) [100°C]

Hard boiling of egg

108

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.

109

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

110

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)

111

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

q = +w

–ΔU = –w

PΔV = 0

q = ΔU

112

The enthalpies of combustion of carbon and carbon monoxide are − 390 KJ and −278 KJ respectively. The enthalpy of formation of CO in kJ is -

668

112

− 112

− 668

113

Hess’s law is used in the determination of

heat of reaction

heat of combustion

heat of formation

all of these.

114

ΔH for CaCO₃(s) → CaO(s) + CO₂(g) is 176 kJ mol⁻¹ at 1240 K. The ΔU for the change is equal to:

160 kJ

165.6 kJ

186.3 kJ

180.0 kJ

115

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)

116

For a certain reaction the change in enthalpy and change in entropy are 40.63 kJ mol⁻¹ and 100 JK⁻¹ mol⁻¹. What is the value of ΔG at 27°C and indicate whether the reaction is spontaneous or not -

+10630 J mol⁻¹; spontaneous

+10630 J mol⁻¹; non spontaneous

− 7990 J mol⁻¹; spontaneous

+ 7900 J mol⁻¹; spontaneous

117

For the reaction, bond energies are given as under – (i) C—C, 346 kJ/mol (ii) C—H, 413 kJ/mol (iii) H—H, 437 kJ/mol and (iv) C=C, 611 kJ/mol What will be the value of ΔH at 25°C for the above reaction ?

−289 kJ mol⁻¹

−124 kJ mol⁻¹

+124 kJ mol⁻¹

+289 kJ mol⁻¹

118

∆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.

119

∆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

120

The bond enthalpies of H₂, X₂ and HX are in the ratio of 2 : 1 : 2. if the enthalpy for formation of HX is − 50 kJ mol⁻¹, the bond enthalpy of H₂ is -

200 kJ mol⁻¹

400 kJ mol⁻¹

100 kJ mol⁻¹

300 kJ mol⁻¹

121

N₂(g) + 2O₂(g) → 2NO₂ + X kJ 2NO(g) + O₂(g) → 2NO₂(g) + Y kJ The enthalpy of formation of NO is

(2X − 2Y)

X − Y

1/2 (Y − X)

1/2 (X − Y)

122

A solution of 500 ml of 0.2 M KOH and 500 ml of 0.2 M HCl is mixed and stirred; the rise in temperature is T₁. The experiment is repeated using 250 ml of each solution, the temperature raised is T₂. Which of the following is true -

T₁ = T₂

T₁ = 2T₂

T₁ = 4T₂

T₂ = 9T₁

123

X g of ethanal (CH₃CHO) was subjected to combustion in a bomb calorimeter and the heat produced is Y Joules. Then which of following is correct -

ΔE(comb.) = − Y kJ

ΔE(comb.) = −(44Y/X) J mol⁻¹

ΔH(comb.) = −(44Y/X) J mol⁻¹

ΔH(comb.) = − Y J mol⁻¹

124

A state function is that -

Which is used in thermochemistry

Which obeys all the laws of thermodynamics

Quantity whose value depends only on the state of the system

Quantity which is used in measuring thermal change

125

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.

126

Which law of thermodynamics helps in calculating the absolute entropies of various substances at different temperatures -

First law

Second law

Third law

Zeroth law

127

For the reaction 2SO₂(g) + O₂(g) → 2SO₃(g) the entropy-

increases

decreases

remains unchanged

change cannot be predicted

128

For an endothermic reaction ΔS is positive. The reaction is -

Spontaneous at all temperatures

Spontaneous when TΔS > ΔH

Spontaneous when ΔH > TΔS

Non Spontaneous at all temperature

129

The solubility product of AgCl is 1.6 × 10⁻¹⁰ and log ksp is −9.80. The value of ΔG° for the process, AgCl (s) + aq ⇌ Ag⁺ (aq) + Cl⁻ (aq) is -

− 55.9 kJ

+ 55.9 kJ

+100.8 kJ

− 100.8 kJ

130

The heat of neutralization of HCN by NaOH is 13.3 kJ/mol, the energy of dissociation of HCN is -

43.8 kJ

−43.8 kJ

−68 kJ

68 kJ

131

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.

132

How many kcal of heat is evolved by the complete neutralisation of one mole sulphuric acid with NaOH -

13.7 kcal

27.4 kcal

6.85 kcal

None of the above

133

Match Bonds in List-I with their bond enthalpies in List-II

List-I List-II

a. H—H (i) 318 kJ mol⁻¹

b. O—H (ii) 464 kJ mol⁻¹

c. H—F (iii) 435.8 kJ mol⁻¹

d. P—H (iv) 569 kJ mol⁻¹

The correct option is

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)

134

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

135

The work done on the system when one mole of an ideal gas at 500 K is compressed isothermally and reversibly to 1/10th of its original volume (R = 2 cal) -

500 kcal

1.51 kcal

− 23.03 kcal

2.303 kcal

136

Latent heat of vaporisation of a liquid at 500 K and 1 atm pressure is 10.00 kcal/mol. What will be the change in internal energy (ΔE) for 3 mol of liquid at same temperature-

13.0 kcal

− 13.0 kcal

27.0 kcal

− 27.0 kcal

137

A mixture of 2 mole of carbon monoxide gas and one mole of dioxygen gas is enclosed in a vessel and is ignited to convert carbon monoxide into carbon dioxide. If the enthalpy change is ΔH and internal energy change is ΔU, then for the above process –

ΔH = ΔU

ΔH + ΔU = 1

ΔH − ΔU > 0

ΔH < ΔU

138

In a change from state A to state B -

'q' depends only on the initial and final state

'w' depends only on the initial and final state

ΔE depends only on the initial and final state

ΔE depends upon the path adopted by A to change into B

139

(i) H₂(g) + Cl₂(g) →2HCl(g) ; Δ H= − x kJ (ii) NaCl + H₂SO₄ → NaHSO₄ +HCl ; Δ H= − y kJ (iii)2H₂O +2Cl₂ →4HCl +O₂ ; Δ H= − z kJ From the above equations, the value of ΔHf of HCl is -

− x kJ

− y kJ

− z kJ

−x/2 kJ

140

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

141

Heat of reaction for

C₆H₁₂O₆ (s) + 6O₂(g) → 6CO₂ (g) + 6H₂O (g)

at constant pressure is –651 Kcal at 17ºC. Calculate the heat of reaction at constant volume at 17ºC

– 554.5 Kcal

– 654.5 Kcal

– 354.5 Kcal

– 154.5 Kcal

142

∆Hneutralisation is;

always positive.

always negative.

always zero.

positive or negative.

143

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

144

Latent heat of vaporisation of water is 540 cal g⁻¹. The entropy change during the evaporation of 1 mole of water at 100°C is -

5.4 cal K⁻¹ mol⁻¹

20 cal K⁻¹ mol⁻¹

25 cal K⁻¹ mol⁻¹

26.06 cal K⁻¹ mol⁻¹

145

Identify the state functions among the following

q–w

q + w

q/w

146

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

147

Which law of thermodynamics introduces the concept of entropy ?

First law

Zeroth law

Third law

Second law

148

The net heat change in a chemical reaction is same whether it is brought about in two or more different ways in one or several steps. It is known as -

Hess's law

Law of conservation of energy

Henry's law

Joule's principle

149

1 gm H₂ gas at S.T.P. is expanded so that volume is doubled. Hence work done is -

−22.4 ℓ-atm

−5.6 ℓ-atm

−11.2 ℓ-atm

−44.8 ℓ-atm

150

H₂ + Cl₂ → 2 HCl; ΔH = − 44K. cals. In this reaction heat of formation of 1 mole of HCl in K. cals is -

− 44.0

+ 44.0

− 22.0

+ 22.0

151

Work done in vaporisation of one mol of water at 373 K against the pressure of 1 atmosphere is approximately -

− 3100.0 J

31.20 J

− 20.2 J

+ 20.2 J

152

Calculate the temperature at which ΔG = − 5.2 kJ mol⁻¹ ΔH = 145.6 kJ mol⁻¹ and ΔS = 216 JK⁻¹ mol⁻¹ for a chemical reaction -

698°C

425°C

650 K

650°C

153

The enthalpies of all elements in their standard states are -

unity

zero

< 0

> 0

154

The heat of combustion of solid benzoic acid at constant volume is −321.30 kJ at 27°C. The heat of combustion at constant pressure is -

−321.30 − 300 R

−321.30 + 300 R

−321.30 − 150 R

−321.30 + 900 R

155

For the process, melting of ice at 260 K the ΔH is -

Negative

Positive

Zero

Cannot be predicted

156

When ethyne is passed through a red hot tube, then formation of benzene takes place - ΔHf°(C₂H₂)(g) = 230 kJ mol⁻¹ ΔHf°(C₆H₆)(g) = 85 kJ mol⁻¹ Calculate the standard heat of trimerisation of ethyne to benzene. 3 C₂H₂(g) ⟶ C₆H₆(g)

205 kJ mol⁻¹

605 kJ mol⁻¹

−605 kJ mol⁻¹

−205 kJ mol⁻¹

157

The lattice energy of solid NaCl is 180 kcal mol⁻¹. The dissolution of the solid in water in the form of ions is endothermic to the extent of 1 kcal mol⁻¹. If the hydration energies of Na⁺ and Cl⁻ ions are in the ratio 6 : 5, what is the enthalpy of hydration of sodium ion?

−85.6 kcal/mol

−97.5 kcal/mol

82.6 kcal/mol

+100 kcal/mol

158

According to Hess's Law the thermal effect of a reaction depends on -

initial concentration of reactants

final condition of the reacting substance

intermediate states of a reaction

initial and final conditions of the reacting substances

159

For a chemical reaction, 2A₂(g) + 5B₂(g) → 2A₂B₅(g), at 27°C the difference between ΔH and ΔE is X. Then the ratio X/R -

Zero

Unity

−5 × 10⁰

−1.5 × 10³

160

The value of ΔH° for the reaction Cu⁺(g) + I⁻(g) → CuI(g) is − 446 kJ mol⁻¹. If the ionization energy of Cu(g) is 745 kJ mol⁻¹ and the electron affinity of I(g) is − 295 kJ mol⁻¹, then the value of ΔH° for the formation of one mole of CuI(g) from Cu(g) and I(g) is -

− 446 kJ

450 kJ

594 kJ

4 kJ

161

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

162

The enthalpy of neutralization of NH₄OH and CH₃COOH is − 10.5 kcal/mole and enthalpy of neutralization of strong base and CH₃COOH is − 12.5 kcal/mole. Calculate the enthalpy of dissociation of NH₄OH –

3.0

4.0

2.0

10.0

163

One mole of a non-ideal gas undergoes a change of state (2.0 atm, 3.0L, 95K) →(4.0 atm, 5.0L, 245 K) with a change in internal energy, ∆U = 30.0 L atm. The change in enthalpy (∆H) of the process in L atm is -

164

Enthalpy change of the reaction 2H (g) → H₂(g) is − 104 kcal The H - H bond dissociation energy is-

104 kcal

−104 kcal

− 52 kcal

+ 52 kcal

165

The heat of formation of water is given by :

H₂(g) + 1/2 O₂(g) → H₂O(l) ; ΔH = −68.3 kcal

2H₂(g) + O₂(g) → 2H₂O(l) ; ΔH = −136.6 kcal

H₂(g) + 1/2 O₂(g) → H₂O(g) ; ΔH = −86 kcal

H₂(g) + 1/2 O₂(g) → H₂O(l) ; ΔH = +68.3 kcal

166

The enthalpy of combustion of a substance -

is always positive

is always negative

can be either zero or greater than zero

is unpredictable till calculations are done

167

The heat produced by complete neutralisation of 100 ml of HNO₃ with 300 ml of decimolar KOH solution is 1.713 kJ. The molarity of HNO₃ solution will be –

0.1

0.3

0.5

168

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)

169

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

volume

mass

heat capacity

temperature.

170

The heat of combustion of benzene determined in a bomb calorimeter is − 870 K.cal. mol⁻¹ at 298 K. The value of ΔE for the reaction is -

− 1740 K. cal mol⁻¹

+ 870 K. cal mol⁻¹

− 870 K. cal mol⁻¹

+ 1740 K. cal mol⁻¹

171

Calculate the bond energy of C-H bond from the following data : (a) C(s) + 2H₂(g) → CH₄(g) ; ΔH = −74.8 KJ (b) H₂(g) → 2H(g) ; ΔH = 435.4 KJ (c) C(s) → C(g) ; ΔH = 718.4 KJ.

316.0 KJ/mol

416 KJ/mol

516 KJ/mol

616.0 KJ/mol

172

The standard free energy change ΔG° is related to equilibrium constant, Kp as -

Kp = −RT ℓn ΔG°

Kp = [ e ]^(−ΔG°/RT)

Kp = − ΔG/RT

Kp = e^(−ΔG°/RT)

173

An equal volume of 1M HCl and 1M H₂SO₄are neutralized by 1M NaOH solution and X and Y KJ/eq. of heat liberated respectively correct relationship is:-

X = 2Y

X = 3Y

X = 4Y

X = Y/2

174

The difference between Δ H and Δ E at constant volume is equal to -

PΔV

VΔP

3/2 R

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