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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

Substracting equation (i) from equation and (ii) multiplied by `3`, we get
i. `2Fe(s) +(3)/(2) O_(2)(g) rarr Fe_(2)O_(3)(g), DeltaH^(Theta) =- 193.4kJ`
ii. `3Mg(s) +(3)/(2) O_(2)(g)rarr 3MgO(s), DeltaH =- 420.6 kJ`
Subtracting (i) from (ii),
`3Mg(s) + Fe_(2)O_(3) rarr 3MgO + 2Fe`,
`DeltaH^(Theta) =- 420.6 -(-193.4) =- 227.2kJ`
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