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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

21.0 kJ

B

`-21.0 kJ`

C

`13.7 kJ`

D

`13.7 kJ.`

Text Solution

Verified by Experts

The correct Answer is:
B
`Delta H_("raction ")=2 Delta_f H^@(MgO) - Delta_f H^@(SiO_2)`
`=29-34.7)-(-48.4) =-21 kJ`
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