1.

Given : `2Fe+(3)/(2)O_(2)rarrFe_(2)O_(3), DeltaH=-193.4 kJ`, `Mg+(1)/(2)O_(2)rarrMgO, DeltaH=-140.2 kJ` What is the `DeltaH` of the reaction `Mg+Fe_(2)O_(3)rarr3MgO+2Fe`A. `-1802 kJ`B. `+1802 kJ`C. `-800 kJ`D. `-228 kJ`

Answer» Correct Answer - D
`2Fe+(3)/(2)O_(2)rarrFe_(2)O_(3), DeltaH=-193.4 kJ " ...(i)"`
`Mg+(1)/(2)O_(2)rarrMgO, DeltaH=-140.2 kJ " ....(ii)"`
On multiplying eq. (ii) by 3
`3Mg+(3)/(2)O_(2)rarr3MgO, DeltaH=-420.6 kJ " ....(ii)"`
Resulting equation can be obtained by subtracting eq. (i) from (iii)
`3Mg+(3)/(2)O_(2)rarr3MgO, DeltaH=-420.6 kJ`
`(2Fe+(3)/(2)O_(2)rarrFe_(2)O_(3), DeltaH=-193.4 kJ)/("Subtraction : ")`
`3Mg+Fe_(2)O_(3)rarr2Fe+3MgO, DeltaH=-227.2 kJ`


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