Chemical Thermodynamics · JEE Main previous year questions

2025 11 questions

1. Q512025 · 8 Apr 2025 · Shift 2

   The atomic number of the element from the following with lowest $1^{\mathrm{st}}$ ionisation enthalpy is :

   1. A.$32$
   2. B.$35$
   3. C.$19$
   4. D.$87$
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   Answer: D

2. Q752025 · 8 Apr 2025 · Shift 2· Numerical answer
   
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   Answer: 98

3. Q592025 · 4 Apr 2025 · Shift 1

   One mole of an ideal gas expands isothermally and reversibly from $10\mathrm{d}{\mathrm{m}}^3$ to $20\mathrm{d}{\mathrm{m}}^3$ at 300 K . $\Delta \mathrm{U}$, q and work done in the process respectively are Given: $\mathrm{R}=8.3\mathrm{J}{\mathrm{K}}^{-1}\mathrm{mo}{\mathrm{l}}^{-1}$ $\ln 10=2.3$ $\log 2=0.30$ $\log 3=0.48$

   1. A.$0,21.84\mathrm{kJ},-1.726\mathrm{J}$
   2. B.$0,21.84\mathrm{kJ},21.84\mathrm{kJ}$
   3. C.$0,1.718\mathrm{kJ},-1.718\mathrm{kJ}$
   4. D.$0,-17.18\mathrm{kJ},1.718\mathrm{J}$
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   Answer: C

4. Q662025 · 4 Apr 2025 · Shift 1

   Let us consider a reversible reaction at temperature, T. In this reaction, both $\Delta \mathrm{H}$ and $\Delta \mathrm{S}$ were observed to have positive values. If the equilibrium temperature is Te , then the reaction becomes spontaneous at:

   1. A.$\mathrm{Te}>\mathrm{T}$
   2. B.$\mathrm{T}>\mathrm{Te}$
   3. C.$\mathrm{T}=\mathrm{Te}$
   4. D.$\mathrm{Te}=5\mathrm{T}$
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   Answer: B

5. Q522025 · 3 Apr 2025 · Shift 1

   Which of the following statements are correct? A. The process of adding an electron to a neutral gaseous atom is always exothermic. B. The process of removing an electron from an isolated gaseous atom is always endothermic. C. The $1^{\text{st}}$ ionization energy of boron is less than that of beryllium. D. The electronegativity of C is 2.5 in $\mathrm{C}{\mathrm{H}}_4$ and $\mathrm{CC}{\mathrm{l}}_4$ E. Li is the most electropositive among elements of group I. Choose the correct answer from the options given below:

   1. A.A, C and D Only
   2. B.B and C Only
   3. C.B and D Only
   4. D.B, C and E Only
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   Answer: B

6. Q742025 · 3 Apr 2025 · Shift 2· Numerical answer
   
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   Answer: 304

7. Q752025 · 3 Apr 2025 · Shift 2· Numerical answer

   A sample of $\mathrm{n}$-octane ($1.14\mathrm{g}$) was completely burnt in excess of oxygen in a bomb calorimeter, whose heat capacity is $5{\mathrm{kJ}\mathrm{K}}^{-1}$. As a result of combustion reaction, the temperature of the calorimeter is increased by $5\mathrm{K}$. The magnitude of the heat of combustion of octane at constant volume is__________ ${\mathrm{kJmol}}^{-1}$ (nearest integer).

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   Answer: 2500

8. Q592025 · 2 Apr 2025 · Shift 2

   Arrange the following in order of magnitude of work done by the system/on the system at constant temperature. (a) $|w_{\text{reversible}}|$ for expansion in infinite stages. (b) $|w_{\text{irreversible}}|$ for expansion in single stage. (c) $|w_{\text{reversible}}|$ for compression in infinite stages. (d) $|w_{\text{irreversible}}|$ for compression in single stage. Choose the correct answer from the options given below :

   1. A.$d>c=a>b$
   2. B.$c=a>d>b$
   3. C.$a>c>b>d$
   4. D.$a>b>c>d$
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   Answer: A

9. Q542025 · 24 Jan 2025 · Shift 2

   $\mathrm{S}(\mathrm{g})+\frac{3}{2}{\mathrm{O}}_2(\mathrm{g})\to \mathrm{S}{\mathrm{O}}_3(\mathrm{g})+2x\text{ kcal}$ $\mathrm{S}{\mathrm{O}}_2(\mathrm{g})+\frac{1}{2}{\mathrm{O}}_2(\mathrm{g})\to \mathrm{S}{\mathrm{O}}_3(\mathrm{g})+y\text{ kcal}$ The heat of formation of $\mathrm{S}{\mathrm{O}}_2(\mathrm{g})$ is given by :

   1. A.$2x+y\text{ kcal}$
   2. B.$\frac{2x}{y}\text{ kcal}$
   3. C.$y-2x\text{ kcal}$
   4. D.$x+y\text{ kcal}$
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   Answer: C

10. Q582025 · 23 Jan 2025 · Shift 2

    The effect of temperature on spontaneity of reactions are represented as : | | $\Delta \mathrm{H}$ | $\Delta \mathrm{S}$ | Temperature | Spontaneity | |---|---|---|---|---| | (A) | $+$ | $-$ | any T | Non spontaneous | | (B) | $+$ | $+$ | low T | spontaneous | | (C) | $-$ | $-$ | low T | Non spontaneous | | (D) | $-$ | $+$ | any T | spontaneous | The incorrect combinations are :

    1. A.(A) and (C) only
    2. B.(B) and (D) only
    3. C.(A) and (D) only
    4. D.(B) and (C) only
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    Answer: D

11. Q722025 · 23 Jan 2025 · Shift 2· Numerical answer

    The bond dissociation enthalpy of ${\mathrm{X}}_2$ $\Delta {\mathrm{H}}_{\mathrm{bond}}^{\circ }$ calculated from the given data is ____ $\mathrm{kJmo}{\mathrm{l}}^{-1}$. (Nearest integer) ${\mathrm{M}}^{+}{\mathrm{X}}^{-}(\mathrm{s})\to {\mathrm{M}}^{+}(\mathrm{g})+{\mathrm{X}}^{-}(\mathrm{g})\mathrm{\Delta }{\mathrm{H}}_{\mathrm{lattice}}^{\circ }=800\mathrm{kJ}\mathrm{mo}{\mathrm{l}}^{-1}$ $\mathrm{M}(\mathrm{s})\to \mathrm{M}(\mathrm{g})\mathrm{\Delta }{\mathrm{H}}_{\mathrm{sub}}^{\circ }=100\mathrm{kJ}\mathrm{mo}{\mathrm{l}}^{-1}$ $\mathrm{M}(\mathrm{g})\to {\mathrm{M}}^{+}(\mathrm{g})+{\mathrm{e}}^{-}(\mathrm{g})\mathrm{\Delta }{\mathrm{H}}_{\mathrm{i}}^{\circ }=500\mathrm{kJ}\mathrm{mo}{\mathrm{l}}^{-1}$ $\mathrm{X}(\mathrm{g})+{\mathrm{e}}^{-}(\mathrm{g})\to {\mathrm{X}}^{-}(\mathrm{g})\mathrm{\Delta }{\mathrm{H}}_{\mathrm{eg}}^{\circ }=-300\mathrm{kJ}\mathrm{mo}{\mathrm{l}}^{-1}$ $\mathrm{M}(\mathrm{s})+\frac{1}{2}{\mathrm{X}}_2(\mathrm{g})\to {\mathrm{M}}^{+}{\mathrm{X}}^{-}(\mathrm{s})\mathrm{\Delta }{\mathrm{H}}_{\mathrm{f}}^{\circ }=-400\mathrm{kJ}\mathrm{mo}{\mathrm{l}}^{-1}$ [Given : ${\mathrm{M}}^{+}{\mathrm{X}}^{-}$ is a pure ionic compound and $\mathrm{X}$ forms a diatomic molecule ${\mathrm{X}}_2$ in gaseous state]

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    Answer: 200