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Consider the following reactions: (i) H_(a q)^++ OH_(a q)^- → H_2 O_( i), Δ H =- X_1 ~kJ ~mol^-1 (ii) H_2(a q)+ 1 2 O_2(a q) → H_2 O_( I) Δ H =- X_2…

NEET UG 2007 — Chemistry Physical Chemistry

2007mcqmedium

Consider the following reactions: (i) H(aq)++OH(aq)−→H2O(i),ΔH\mathrm{H}_{(a q)}^{+}+\mathrm{OH}_{(a q)}^{-} \rightarrow \mathrm{H}_2 \mathrm{O}_{(\mathrm{i})}, \Delta \mathrm{H}H(aq)+​+OH(aq)−​→H2​O(i)​,ΔH =−X1 kJ mol−1=-\mathrm{X}_1 \mathrm{~kJ} \mathrm{~mol}^{-1}=−X1​ kJ mol−1 (ii) H2(aq)+12O2(aq)→H2O(I)ΔH\mathrm{H}_{2(a q)}+\frac{1}{2} \mathrm{O}_{2(a q)} \rightarrow \mathrm{H}_2 \mathrm{O}_{(\mathrm{I})} \Delta \mathrm{H}H2(aq)​+21​O2(aq)​→H2​O(I)​ΔH =−X2 kJ mol−1=-\mathrm{X}_2 \mathrm{~kJ} \mathrm{~mol}^{-1}=−X2​ kJ mol−1 (iii) CO2( g)+H2(g)→CO(g)+H2O,ΔH\mathrm{CO}_{2(\mathrm{~g})}+\mathrm{H}_{2(g)} \rightarrow \mathrm{CO}_{(g)}+\mathrm{H}_2 \mathrm{O}, \Delta \mathrm{H}CO2( g)​+H2(g)​→CO(g)​+H2​O,ΔH =−X3 kJ mol−1=-\mathrm{X}_3 \mathrm{~kJ} \mathrm{~mol}^{-1}=−X3​ kJ mol−1 (iv) C2H2(g)+52O2(g)→2CO2(g)+H2O(i), \mathrm{C}_2 \mathrm{H}_{2(g)}+\frac{5}{2} \mathrm{O}_{2(g)} \rightarrow 2 \mathrm{CO}_{2(g)}+\mathrm{H}_2 \mathrm{O}_{(i) \text {, }}C2​H2(g)​+25​O2(g)​→2CO2(g)​+H2​O(i), ​ ΔH=+X4 kJ mol−1\Delta \mathrm{H}=+\mathrm{X}_4 \mathrm{~kJ} \mathrm{~mol}^{-1}ΔH=+X4​ kJ mol−1 Enthalpy of formation of H2O(l)\mathrm{H}_2 \mathrm{O}_{(l)}H2​O(l)​ is:

Official previous-year question

Held on 30 Apr 2007 · Verified 9 Jul 2026.

Options

  1. A

    +X3 kJ mol−1+\mathrm{X}_3 \mathrm{~kJ} \mathrm{~mol}^{-1}+X3​ kJ mol−1

  2. B

    −X4 kJ mol−1-\mathrm{X}_4 \mathrm{~kJ} \mathrm{~mol}^{-1}−X4​ kJ mol−1

  3. C

    +X1 kJ mol−1+\mathrm{X}_1 \mathrm{~kJ} \mathrm{~mol}^{-1}+X1​ kJ mol−1

  4. D

    −X2 kJmol−1-\mathrm{X}_2 \mathrm{~kJ}^{\mathrm{mol}}{ }^{-1}−X2​ kJmol−1

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