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5. Thermodynamics and thermochemistry — Chemistry STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 ScienceChemistry5. Thermodynamics and thermochemistry1 Mark
MCQ
The incubation heat of $ SiO_2 $ and $MgO$  is respectively $-48.4 $ and $ 34.7\,kJ$.

The heat of the reaction $2Mg + Si{O_2} \to 2MgO + Si$ is......$kJ$

  • A
    $21.16$
  • ✓
    $ - 21.10$
  • C
    $ - 13.62$
  • D
    $13.6$
✓

Answer

Correct option: B.
$ - 21.10$
(b)$\Delta {H_{({\rm{reaction}})}} = 2\Delta H_f^o\,(MgO) = - \Delta H_f^o\,(Si{O_2})$
$ = 2\,( - \,34.7) - ( - \,48.4) = - 21\,kJ.$

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