Thermodynamic Laws and Thermochemistry - Thermodynamics - Life Sciences Previous Year Questions

1

2007 · Life Sciences · Thermodynamics · Thermodynamic Laws and Thermochemistry

Life Sciences (XL) 2007

For the reaction A ⇌ B, the activation energy for the forward reaction is 123 kJ/mol. The activation energy for the reverse reaction is 140 kJ/mol. The enthalpy change for the forward reaction is

A

263 kJ/mol

B

-263 kJ/mol

C

17 kJ/mol

D

-17 kJ/mol

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2

2007 · Life Sciences · Thermodynamics · Thermodynamic Laws and Thermochemistry

Life Sciences (XL) 2007

Assuming that the standard enthalpy change (ΔH°) for the above reaction is constant in this temperature range, its value is

A

33.3 kJ/mol

B

76.6 kJ/mol

C

-33.3 kJ/mol

D

-76.6 kJ/mol

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3

2008 · Life Sciences · Thermodynamics · Thermodynamic Laws and Thermochemistry

Life Sciences (XL) 2008

Liquid bromine boils at 59 °C. Assuming it to be a normal liquid, which of the following gives its standard molar enthalpy of vaporization?

A

\((8.314 \times 332)\) J mol\(^{-1}\)

B

\((85 \times 332)\) J mol\(^{-1}\)

C

\((332 / 85)\) J mol\(^{-1}\)

D

\((332 / 8.314)\) J mol\(^{-1}\)

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4

2011 · Life Sciences · Thermodynamics · Thermodynamic Laws and Thermochemistry

Life Sciences (XL) 2011

Trouton’s rule is obeyed by

A

hydrogen

B

methanol

C

benzene

D

acetic acid

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5

2013 · Life Sciences · Thermodynamics · Thermodynamic Laws and Thermochemistry

Life Sciences (XL) 2013

The given equation \[ \left(\frac{d(\Delta H)}{dT}\right)_p = \Delta C_p \] where \(H\), \(T\) and \(C_p\) are the enthalpy, temperature and heat capacity at constant pressure, respectively, is called

A

Clausius-Clapeyron equation

B

Hess's law

C

Kirchhoff's equation

D

Trouton's rule

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6

2014 · Life Sciences · Thermodynamics · Thermodynamic Laws and Thermochemistry

Life Sciences (XL) 2014

At 298 K, the bond dissociation energies of C–H, C–C and C=C are 415, 344 and 615 kJ mol\(^{-1}\), respectively. The enthalpy of atomization of carbon is 717 kJ mol\(^{-1}\) and that of hydrogen is 218 kJ mol\(^{-1}\). The heat of formation of naphthalene at 298 K is _____ kJ mol\(^{-1}\).

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7

2014 · Life Sciences · Thermodynamics · Thermodynamic Laws and Thermochemistry

Life Sciences (XL) 2014

Assuming ideal behavior, the density of fluorine gas at 20 °C and 0.3 atm is ____ g L\(^{-1}\). (Molecular weight of \(F_2\) = 38 g mol\(^{-1}\), R = 0.082 L atm mol\(^{-1}\) K\(^{-1}\))

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8

2016 · Life Sciences · Thermodynamics · Thermodynamic Laws and Thermochemistry

Life Sciences (XL) 2016

Combinations of a process and equation are given below. The INCORRECT combination is

A

Constant pressure heating with no phase change; \(w = -\int_{1}^{2} P \, dV \)

B

Reversible adiabatic process in a perfect gas; \(\Delta U = \int_{1}^{2} C_V (T) dT \)

C

Reversible isothermal process in a perfect gas; \(w_{rev} = -\int_{1}^{2} P \, dV \)

D

Constant volume heating with no phase change; \(\Delta U = \int_{1}^{2} C_V dT \)

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9

2016 · Life Sciences · Thermodynamics · Thermodynamic Laws and Thermochemistry

Life Sciences (XL) 2016

For propene at 298 K, the molar enthalpy of hydrogenation is \( -124.27 \text{ kJ mol}^{-1} \) and the standard enthalpy of formation is \( 20.42 \text{ kJ mol}^{-1} \). For propane at 298 K, the standard enthalpy of formation in kJ mol^-1 is ______________.

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10

2017 · Life Sciences · Thermodynamics · Thermodynamic Laws and Thermochemistry

Life Sciences (XL) 2017

The extensive quantity among the following is

A

Pressure

B

Temperature

C

Chemical potential

D

Volume

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11

2018 · Life Sciences · Thermodynamics · Thermodynamic Laws and Thermochemistry

Life Sciences (XL) 2018

For the complete combustion of graphite and diamond in oxygen individually, the standard enthalpy change (ΔH°₂₉₈) values are –393.5 kJ mol^–1 and –395.4 kJ mol^–1, respectively. Then, the ΔH°₂₉₈ for the conversion of graphite into diamond is

A

+1.9 kJ mol^–1

B

–1.9 kJ mol^–1

C

+3.8 kJ mol^–1

D

–3.8 kJ mol^–1

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12

2020 · Life Sciences · Thermodynamics · Thermodynamic Laws and Thermochemistry

Life Sciences (XL) 2020

The standard enthalpy of reaction (in kJ mol^-1) for obtaining three moles of H₂ (g) from atomic hydrogen in gas phase is __________. (Given: Standard enthalpy of formation of atomic hydrogen in gas phase is 218 kJ mol^-1)

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13

2021 · Life Sciences · Thermodynamics · Thermodynamic Laws and Thermochemistry

Life Sciences (XL) 2021

Given the following standard heats of formation, $\Delta_f H^\circ(P_4, g) = 314.6 \text{ kJ mol}^{-1}$, $\Delta_f H^\circ(PH_3, g) = 5.4 \text{ kJ mol}^{-1}$, and $\Delta_f H^\circ(H, g) = 218.0 \text{ kJ mol}^{-1}$, the average bond enthalpy of a P–H bond in PH3(g) is ________ kJ mol⁻¹ (rounded off to one decimal place).

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14

2023 · Life Sciences · Thermodynamics · Thermodynamic Laws and Thermochemistry

Life Sciences (XL) 2023

Consider two different paths in which the volume of an ideal gas doubles isothermally:
i) Reversible expansion (work done = W_rev)
ii) Irreversible expansion, with the external pressure equal to the final pressure of the gas (work done = W_irrev)
Here, W_rev/W_irrev = __________.

A

2 ln 2

B

\(\frac{1}{2} \ln 2 \)

C

\(\frac{1}{2} \ln \frac{1}{2} \)

D

\(2 \ln \frac{1}{2} \)

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15

2024 · Life Sciences · Thermodynamics · Thermodynamic Laws and Thermochemistry

Life Sciences (XL) 2024

One mole of an ideal gas expands isothermally and reversibly to double its volume. If the expansion work done by the system is 1728.85 J, the temperature of the system is ______ K (rounded off to 2 decimal places).

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16

2025 · Life Sciences · Thermodynamics · Thermodynamic Laws and Thermochemistry

Life Sciences (XL) 2025

The standard enthalpy of the reaction,
\( C(\text{graphite}) + H_2O (g) \rightarrow CO (g) + H_2 (g) \) is found to be +131.3 kJ mol⁻¹ and the \( \Delta_f H^0 \) value for CO (g) is –110.5 kJ mol⁻¹.
The value of \( \Delta_f H^0 \) (in kJ mol⁻¹) for H₂O (g) is
(The standard enthalpies of formation of elements in their reference states are zero at all temperatures)

A

+241.8

B

0.0

C

–241.8

D

+20.8

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17

2025 · Life Sciences · Thermodynamics · Thermodynamic Laws and Thermochemistry

Life Sciences (XL) 2025

The isothermal expansion of one mole of an ideal gas from \( V_i \) to \( V_f \) at temperature, T occurs in two ways.
Path I: a reversible isothermal expansion;
Path II: free expansion against zero external pressure
The CORRECT option for the values of \( \Delta U \), \( q \) and \( w \) for Path I and Path II is

A

Path I: \(\Delta U = 0, q > 0, w < 0 \)
Path II: \(\Delta U = 0, q = 0, w = 0 \)

B

Path I: \(\Delta U = 0, q > 0, w < 0 \)
Path II: \(\Delta U > 0, q > 0, w = 0 \)

C

Path I: \(\Delta U = 0, q < 0, w > 0 \)
Path II: \(\Delta U = 0, q > 0, w < 0 \)

D

Path I: \(\Delta U = 0, q < 0, w > 0 \)
Path II: \(\Delta U < 0, q = 0, w = 0 \)

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18

2026 · Life Sciences · Thermodynamics · Thermodynamic Laws and Thermochemistry

Life Sciences (XL) 2026

An ideal gas in an insulated container expands against zero external pressure. For this expansion, the CORRECT statement is

A

Work is done by the gas

B

Work is done on the gas

C

Pressure of the gas remains unchanged

D

Temperature of the gas remains unchanged

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19

2026 · Life Sciences · Thermodynamics · Thermodynamic Laws and Thermochemistry

Life Sciences (XL) 2026

For a given temperature difference between the top and bottom surfaces of a flat metal plate, Fourier’s law of heat conduction implies that

A

temperature gradient increases with increase in heat transfer area

B

heat flux is proportional to the thermal conductivity of the metal

C

heat flux increases with increase in thickness of the metal plate

D

temperature gradient decreases with increase in thickness of the metal plate

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