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The enthalpies of formation of Al(2)O(3)...

The enthalpies of formation of `Al_(2)O_(3)` and `Cr_(2)O_(3)` are `-1596KJ` and `-1134KJ` respectively. `DeltaH` for the reaction
`2Al+Cr_(2)O_(2)rarr2Cr+Al_(2)O_(3)` is

A

`-2730 kJ`

B

`-462 kJ`

C

`-1365 kJ`

D

`+2730 kJ`

Text Solution

Verified by Experts

The correct Answer is:
B
According to equation,
`2Al + 3/2 O_(2) to Al_(2)O_(3) , " "Delta H = -1596 kJ`….(i)
`2Cr + 3/2 O_(2) to Cr_(2)O_(3), " "Delta H = -1134 J` …..(ii)
Reversing Equation (ii) and adding both reactions, we get :
`2Al _ Cr_(2)O_(3) to 2Cr + Al_(2)O_(3) , Delta H = -4.62 kJ`.
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