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Values of heats of formation for SiO(2) ...

Values of heats of formation for `SiO_(2)` and `MgO` are `-48.4` and `-34.7 kJ` respectively. The heat of the reaction `2Mg+SiO_(2)rarr2MgO+Si` is

A

21.16 kJ

B

`-21.0 kJ`

C

`-13.62` kJ

D

13.6 kJ

Text Solution

Verified by Experts

The correct Answer is:
B
`DeltaH_(("reaction"))=2DeltaH_(f)^(@)(MgO)=-DeltaH_(f)^(@)(SiO_(2))`
`=2(-34.7)-(-48.4)=-21 kJ`.
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