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30/09/2021 10:21 am
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The enthalpies of formation of Al2O3 and Cr2O3 are -1596 kJ and -1134 kJ respectively. ΔH for the reaction 2Al + Cr2O3 → 3Cr + Al2O3 is
(a) -2730 kJ
(b) -462 kJ
(c) -1365 kJ
(d) +2730 kJ
1 Answer
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30/09/2021 10:26 am
Correct answer: (b) -462 kJ
Explanation:
2Al + 3/2O2 → Al2O3, ΔH = -1596 kJ .....(i)
2Cr + 3/2O2 → Cr2O3, ΔH = -1134 kJ .....(ii)
By (i) – (ii)
2Al + Cr2O3 → 2Cr + Al2O3, ΔH = -462 kJ