1.

Given :2Fe+(3)/(2)O_(2)rarrFe_(2)O_(3), DeltaH=-193.4 kJ,Mg+(1)/(2)O_(2)rarrMgO, DeltaH=-140.2 kJWhat is the DeltaH of the reactionMg+Fe_(2)O_(3)rarr3MgO+2Fe

Answer»

`-1802 KJ`
`+1802 kJ`
`-800 kJ`
`-228 kJ`

Solution :`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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