1.

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)` isA. `-1365 kJ`B. `+2730 kJ`C. `-2730 kJ`D. `-462 kJ`

Answer» Correct Answer - D
`DeltaH=sumDeltaH_(f)("Products")-sumDeltaH_(f)("reactants")`
`=DeltaH_(f)(Al_(2)O_(3))-DeltaH_(f)(Cr_(2)O_(3))`
[`DeltaH_(f)` of elements in standard state `=0`]
`=-1596 kJ-(-1134 kJ)`
`=1134 kJ-1596kJ=-462 kJ`


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