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The standard enthalpy of formation of H(...

The standard enthalpy of formation of `H_(2)O(l)` and `Fe_(2)O_(3)(s)` are respectively `-286 kJ mol^(-1)` and `-824 kJ mol^(-1)`. What is the standard enthalpy change for the following raction ?
`Fe_(2)O_(3)(s) + H_(2)(g) rarr 3H_(2)O(l) + 2Fe(s)`

A

`-538 kJ mol^(-1)`

B

`+538 kJ mol^(-1)`

C

`-102 k J mol^(-1)`

D

`-34 kJ mol^(-1)`

Text Solution

Verified by Experts

The correct Answer is:
D
Given reaction,
`Fe_(2)O_(3)(s) + 3H_(2)(g) rarr 3H_(2)O(l)+2Fe(s)`
and `H_(f)^(@) (H_(2)O) = -286.00 kJ//mol`
`H_(f)^(@)(F_(2)O_(3)) = -824 kJ//mol`
Therefore, `H_(R)` (Heat of reaction)
`= Sigma H_(f)^(@)` (products) `- Sigma H_(f)^(@)` (reactants)
`H_(R) = -(3 xx 286) - (-824)`
`because (H_(f)^(@) " and Fe = 0")`
`H_(R) = -858 + 824`
`H_(R) = -34 kJ//mol`
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