PYQs Homework Notes Mocks Board Daily Homework JEE Mains Chemistry Question type Born-Haber cycle: lattice enthalpy or bond dissociation enthalpy This type of question, asked 2 times: 23 Jan 2025, 22 Jan 2026 S2. All 2 questions below, oldest first.
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Question 1 23 Jan 2025
124 The bond dissociation enthalpy of X 2 X_{2} X 2 , Δ H bond ∘ \Delta H_{\text{bond}}^{\circ} Δ H bond ∘ , calculated from the given data is _ _ _ _ _ \_\_\_\_\_ _____ k J m o l − 1 kJmol^{- 1} k J m o l − 1 . (Nearest integer) M + X − ( s ) → M + ( g ) + X − ( g ) Δ H lattice ∘ = 800 k J m o l − 1 M ( s ) → M ( g ) Δ H sub ∘ = 100 k J m o l − 1 M ( g ) → M + ( g ) + e − ( g ) Δ H ∘ i = 500 k J m o l − 1 X ( g ) + e − ( g ) → X − ( g ) Δ H ∘ e g = − 300 k J m o l − 1 M ( s ) + 1 2 X 2 ( g ) → M + X − ( s ) Δ H f ∘ = − 400 k J m o l − 1 \begin{matrix} & M^{+}X^{-}(s) \rightarrow M^{+}(g) +X^{-}(g)\Delta H_{\text{lattice~}}^{\circ}= 800\text{ }kJ{\text{ }mol}^{- 1} \\ & M(\text{ }s) \rightarrow M(\text{ }g)\Delta H_{\text{sub~}}^{\circ}= 100\text{ }kJ{\text{ }mol}^{- 1} \\ & M(\text{ }g) \rightarrow M^{+}(g)+e^{-}(g)\Delta H^{\circ}\ _{i}= 500\text{ }kJ{\text{ }mol}^{- 1} \\ & X(\text{ }g) +e^{-}(g) \rightarrow X^{-}(g)\Delta H^{\circ}\ _{eg}= - 300\text{ }kJ{\text{ }mol}^{- 1} \\ & M(\text{ }s) +\frac{1}{2}X_{2}(\text{ }g) \rightarrow M^{+}X^{-}(s)\Delta H_{f}^{\circ}= - 400\text{ }kJ{\text{ }mol}^{- 1} \end{matrix} M + X − ( s ) → M + ( g ) + X − ( g ) Δ H lattice ∘ = 800 k J m o l − 1 M ( s ) → M ( g ) Δ H sub ∘ = 100 k J m o l − 1 M ( g ) → M + ( g ) + e − ( g ) Δ H ∘ i = 500 k J m o l − 1 X ( g ) + e − ( g ) → X − ( g ) Δ H ∘ e g = − 300 k J m o l − 1 M ( s ) + 2 1 X 2 ( g ) → M + X − ( s ) Δ H f ∘ = − 400 k J m o l − 1 [Given : M + X − M^{+}X^{-} M + X − is a pure ionic compound and X forms a diatomic molecule X 2 X_{2} X 2 in gaseous state]
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Question 2 22 Jan 2026 S2
47 If the enthalpy of sublimation of Li is 155 k J m o l − 1 155\text{ }kJ{\text{ }mol}^{- 1} 155 k J m o l − 1 , enthalpy of dissociation of F 2 F_{2} F 2 is 150 k J m o l − 1 150\text{ }kJ{\text{ }mol}^{- 1} 150 k J m o l − 1 , ionization enthalpy of Li is 520 k J m o l − 1 520\text{ }kJ{\text{ }mol}^{- 1} 520 k J m o l − 1 , electron gain enthalpy of F F F is − 313 k J m o l − 1 - 313\text{ }kJ{\text{ }mol}^{- 1} − 313 k J m o l − 1 , standard enthalpy of formation of LiF is − 594 k J m o l − 1 - 594\text{ }kJ{\text{ }mol}^{- 1} − 594 k J m o l − 1 . The magnitude of lattice enthalpy of LiF is _ _ _ _ \_\_\_\_ ____ k J m o l − 1 kJ{mol}^{- 1} k J m o l − 1 (Nearest integer).
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