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Given: i. 2Fe(s) +(3)/(2)O(2)(g) rarr ...

Given:
i. `2Fe(s) +(3)/(2)O_(2)(g) rarr Fe_(2)O_(3)(s), DeltaH^(Theta) =- 193.4 kJ`
ii. `Mg(s) +(1)/(2)O_(2)(g) rarr MgO(s), DeltaH^(Theta) =- 140.2kJ`
What is `DeltaH^(Theta)`of the reaction?
`3Mg +Fe_(2)O_(3)rarr 3MgO +2Fe`

A

`-227.2kJ`

B

`-272.3kJ`

C

`227.2kJ`

D

`272.3kJ`

Text Solution

Verified by Experts

The correct Answer is:
A
Eq. (ii) multiplied by 3,
`2Fe(s)+(3)/(2)O_(2)(g)toFe_(2)O_(3)(s)" "(DeltaH=-193.4kJ)` . . .(i)
`3Mg(s)+(3)/(2)O_(2)(g)to3MgO(s)" "(DeltaH=-420.6kJ)` . . .(iii)
Subtracting eq. (i) from (iii),
`3Mg(s)+Fe_(2)O_(3)to3MgO+2Fe,DeltaH=-420.6-(-193.4)=-227.2kJ`
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