MCQ
Heat of formation of ${H_2}O$ is $ - 188\,kJ/mole$ and ${H_2}{O_2}$ is $ - 286\,kJ/mole.$ The enthalpy change for the reaction $2{H_2}{O_2}\, \to \,2{H_2}O + {O_2}$ is......$kJ$
- ✓$196 $
- B$-196 $
- C$984$
- D$-984$
✓
Answer
Correct option: A.
$196 $
(a) ${H_2} + \frac{1}{2}{O_2} \to {H_2}O\,\,\,\Delta H = - 188\,kJ/mole$..…..$(i)$
${H_2} + {O_2} \to {H_2}{O_2};\,\,\,\Delta H = - 286\,kJ/mole$..….$(ii)$
By $2 × (i)$ and $(ii)$
$2{H_2} + {O_2} \to 2{H_{2}}O\,;\,\,\Delta H = - 376\,kJ/mole$…..$(iii)$
$2{H_2} + 2{O_2} \to 2{H_2}{O_2}\,\,\,\Delta H = - 572\,kJ/mole$…..$(iv)$
By $(iii) -(iv)$
$2{H_2}{O_2} \to 2{H_2}O + {O_2}\,\,\,\Delta H = + 196\,kJ$.
${H_2} + {O_2} \to {H_2}{O_2};\,\,\,\Delta H = - 286\,kJ/mole$..….$(ii)$
By $2 × (i)$ and $(ii)$
$2{H_2} + {O_2} \to 2{H_{2}}O\,;\,\,\Delta H = - 376\,kJ/mole$…..$(iii)$
$2{H_2} + 2{O_2} \to 2{H_2}{O_2}\,\,\,\Delta H = - 572\,kJ/mole$…..$(iv)$
By $(iii) -(iv)$
$2{H_2}{O_2} \to 2{H_2}O + {O_2}\,\,\,\Delta H = + 196\,kJ$.
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