QJEEM21Ch70d2: JEE Main 2021 Chemistry - Class 11 JEEM21Ch70d2 Solution: The standard enthalpies of formation of Al 2 O 3 and CaO are −…

Question

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The standard enthalpies of formation of Al₂O₃ and CaO are

-

1675 kJ mol^-1 and

-

635 kJ mol^{$-$ 1} respectively.

For the reaction

3CaO + 2Al

\to

3Ca + Al₂O₃ the standard reaction enthalpy

Δ

_rH⁰ = _________ kJ.

(Round off to the Nearest Integer)

Accepted Answer

3 C a O + 2 A l \underset{}{⟶} 3 C a + A l_{2} O_{3}

Δ H_{r e a c t i o n}^{o} = 3 Δ {H^{o}}_{f} (C a, s) + Δ {H^{o}}_{f} (A l_{2} O_{3}, s) - 3 Δ {H^{o}}_{f} (C a O, s) - 2 Δ {H^{o}}_{f} (A l, S)

= 0 + (- 1675) - 3 (- 635) - 0

= - 1675 + 1905

= 230

KJ

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