Chemical Thermodynamics · JEE Main previous year questions

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2026 16 questions

Q742026 · 8 Apr 2026 · Shift 2· Numerical answer
Consider the reaction $2 H_{2} S (g) + 3 O_{2} (g) \to 2 H_{2} O (l) + 2 S O_{2} (g)$ The magnitude of enthalpy change for the reaction in $kJ mo l^{- 1}$ is ____. (Nearest integer) Given : $Δ_{f} H^{⊖} (H_{2} S) = - 20.1 kJ mo l^{- 1}$ $Δ_{f} H^{⊖} (H_{2} O) = - 286.0 kJ mo l^{- 1}$ $Δ_{f} H^{⊖} (S O_{2}) = - 297.0 kJ mo l^{- 1}$
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Answer: 1126
Q552026 · 6 Apr 2026 · Shift 1
Arrange the following isothermal processes in order of the magnitude of the work $(p - V)$ involved between states 1 and 2. A. Expansion in single stage $w_{A}$ B. Expansion in multi stages $w_{B}$ C. Compression in single stage $w_{C}$ D. Compression in multi stages $w_{D}$ Choose the correct option.
1. A. $∣ w_{B} ∣ > ∣ w_{A} ∣ > ∣ w_{C} ∣ > ∣ w_{D} ∣$
2. B. $∣ w_{C} ∣ > ∣ w_{D} ∣ > ∣ w_{A} ∣ > ∣ w_{B} ∣$
3. C. $∣ w_{C} ∣ > ∣ w_{D} ∣ > ∣ w_{B} ∣ > ∣ w_{A} ∣$
4. D. $∣ w_{B} ∣ > ∣ w_{A} ∣ > ∣ w_{D} ∣ > ∣ w_{C} ∣$
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Answer: C
Q542026 · 6 Apr 2026 · Shift 2
Match List - I with List - II. Given $V_{1}$ and $V_{2}$ are initial and final volumes respectively. List - I (Isothermal process) A. Reversible expansion B. Free expansion C. Irreversible Compression D. Cyclic reversible List - II (Expression) I. $q = 0$ II. $q = n R T ln \frac{V _{2}}{V _{1}}$ III. $w = - P_{ext} (V_{1} - V_{2})$ IV. $\frac{q _{rev}}{T} = 0$ Choose the correct answer from the options given below :
1. A.A-II, B-III, C-I, D-IV
2. B.A-II, B-I, C-IV, D-III
3. C.A-II, B-I, C-III, D-IV
4. D.A-I, B-II, C-III, D-IV
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Answer: C
Q602026 · 6 Apr 2026 · Shift 2
The correct order of first ( $Δ_{i} H_{1}$ ) and second ( $Δ_{i} H_{2}$ ) ionisation enthalpy values of Cr and Mn are : A. $Δ_{i} H_{1} : Cr > Mn$ B. $Δ_{i} H_{2} : Cr > Mn$ C. $Δ_{i} H_{1} : Mn > Cr$ D. $Δ_{i} H_{2} : Mn > Cr$ Choose the correct answer from the options given below :
1. A.A and B only
2. B.B and C only
3. C.A and D only
4. D.C and D only
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Answer: B
Q572026 · 4 Apr 2026 · Shift 2
The $1^{st}$ ionization enthalpy for $Mg$ is $+ 737 kJ/mol$ . The most probable estimated value of the $2^{nd}$ ionization enthalpy of $Mg$ is ____.
1. A. $- 906 kJ/mol$
2. B. $- 856 kJ/mol$
3. C. $+ 1450 kJ/mol$
4. D. $+ 590 kJ/mol$
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Answer: C
Q712026 · 4 Apr 2026 · Shift 2· Numerical answer
If $3.365 g$ of ethanol ( $l$ ) is burnt completely in a bomb calorimeter at $298.15 K$ , the heat produced is $99.472 kJ$ . The $∣Δ H_{f}^{\circ} ∣$ of ethanol at $298.15 K$ is ____ $\times 1 0^{2} kJ mo l^{- 1}$ . (Nearest integer) Given: Standard enthalpy for combustion of graphite $= - 393.5 kJ mo l^{- 1}$ Standard enthalpy of formation of water (l) $= - 285.8 kJ mo l^{- 1}$ Molar mass in $g mo l^{- 1}$ of C, H, O are 12 , 1 and 16 respectively
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Answer: 3
Q542026 · 2 Apr 2026 · Shift 1
Consider the following data. (i) $2Al (s) + 6HCl (aq) \to A l_{2} C l_{6} (aq) + 3 H_{2} (g) + 1200 kJ/mol$ (ii) $H_{2} (g) + C l_{2} (g) \to 2HCl (g) + 164 kJ/mol.$ (iii) $HCl (g) + aq \to HCl (aq) + 83 kJ/mol.$ (iv) $A l_{2} C l_{6} (s) + aq \to A l_{2} C l_{6} (aq) + 663 kJ/mol$ The enthalpy of formation of anhydrous solid $A l_{2} C l_{6}$ is :
1. A. $- 648 kJ mo l^{- 1}$
2. B. $- 1350 kJ mo l^{- 1}$
3. C. $- 2002 kJ mo l^{- 1}$
4. D. $- 1527 kJ mo l^{- 1}$
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Answer: D
Q592026 · 2 Apr 2026 · Shift 1
Given below are two statements : Statement (I) : The first ionisation enthalpy of the elements Na, Mg, Cl and Ar follows the order $Na > Mg > Cl > Ar.$ Statement (II) : Among Ca, Al, Fe and B, the third ionisation enthalpy is very high for Ca. In the light of the above statements, choose the correct answer from the options given below :
1. A.Both Statement I and Statement II are true
2. B.Both Statement I and Statement II are false
3. C.Statement I is true but Statement II is false
4. D.Statement I is false but Statement II is true
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Answer: D
Q542026 · 2 Apr 2026 · Shift 2
Gas 'A' undergoes change from state 'X' to state 'Y'. In this process, the heat absorbed and work done by the gas is $10 J$ and $18 J$ respectively. Now gas is brought back to state 'X' by another process during which $6 J$ of heat is evolved. In the reverse process of 'Y' to 'X',
1. A. $18 J$ of the work is done by the gas 'A'.
2. B. $2 J$ of the work is done by the gas 'A'.
3. C. $12 J$ of the work is done on the gas 'A' by the surrounding.
4. D. $14 J$ of the work is done on the gas 'A' by the surrounding.
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Answer: D
Q592026 · 2 Apr 2026 · Shift 2
Given below are two statements : Statement I : The second ionization enthalpy of B, Al and Ga is in the order of $B > Al > Ga$ . Statement II : The correct order in terms of first ionization enthalpy is $Si < Ge < Pb < Sn$ . In the light of the above statements, choose the correct answer from the options given below :
1. A.Both Statement I and Statement II are true
2. B.Both Statement I and Statement II are false
3. C.Statement I is true but Statement II is false
4. D.Statement I is false but Statement II is true
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Answer: B
Q702026 · 2 Apr 2026 · Shift 2
Among $F e^{2 +}$ , $F e^{3 +}$ , $C r^{2 +}$ and $Z n^{2 +}$ , the ion that shows positive borax bead test and with highest ionisation enthalpy is :
1. A. $F e^{2 +}$
2. B. $Z n^{2 +}$
3. C. $C r^{2 +}$
4. D. $F e^{3 +}$
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Answer: D
Q522026 · 24 Jan 2026 · Shift 1
Match the LIST-I with LIST-II $List-I Isothermal process for ideal gas system A. B. C. D. Reversible expansion Free expansion Irreversible expansion Irreversible compression List-II Work done (V_{f} > V_{i}) I. II. III. IV. w = 0 w = - n R T ln (\frac{V _{f}}{V _{i}}) w = - p_{ex} (V_{f} - V_{i}) w = - p_{ex} (V_{i} - V_{f})$ Choose the correct answer from the options given below:
1. A.A-IV, B-I, C-III, D-II
2. B.A-I, B-III, C-II, D-IV
3. C.A-II, B-I, C-III, D-IV
4. D.A-IV, B-II, C-III, D-I
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Answer: C
Q602026 · 24 Jan 2026 · Shift 1
1. A.
2. B.
3. C.
4. D.
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Answer: D
Q682026 · 22 Jan 2026 · Shift 1
Match the LIST-I with LIST-II $List-I Thermodynamic Process A. Work done in reversible, isothermal expansion of 2 mol of ideal gas from 2 d m^{3} to 20 d m^{3} at 300 K . B. Work done in irreversible isothermal expansion of 1 mol ideal gas from 1 m^{3} to 3 m^{3} at 300 K against a constant pressure of 3 kPa . C. Change in internal energy for adiabatic expansion of a 1 mol ideal gas with change of temperature = 320 K and \overline{C}_{V} = \frac{3}{2} R . D. Change in enthalpy at constant pressure of 1 mol ideal gas with change of temperature = 337 K and \overline{C}_{p} = \frac{5}{2} R . List-II Magnitude in kJ I. 4 II. 11.5 III. 6 IV. 7$
1. A.A-I, B-II, C-III, D-IV
2. B.A-III, B-II, C-IV, D-I
3. C.A-II, B-I, C-III, D-IV
4. D.A-II, B-III, C-I, D-IV
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Answer: D
Q592026 · 21 Jan 2026 · Shift 1
1. A.
2. B.
3. C.
4. D.
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Answer: A
Q652026 · 21 Jan 2026 · Shift 2
Given below are two statements : Statement I : The correct order in terms of bond dissociation enthalpy is $C l_{2} > B r_{2} > F_{2} > I_{2}$ . Statement II : The correct trend in the covalent character of the metal halides is $[SnC l_{4} > SnC l_{2}]$ , $[PbC l_{4} > PbC l_{2}]$ and $[U F_{4} > U F_{6}]$ . In the light of the above statements, choose the correct answer from the options given below :
1. A.Both Statement I and Statement II are true
2. B.Both Statement I and Statement II are false
3. C.Statement I is false but Statement II is true
4. D.Statement I is true but Statement II is false
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Answer: D