The standard enthalpies of formation of Al _ 2 O _ 3 and CaO are -1675 , kJ , mol ^ -1 and -635 , kJ , mol ^ -1 respectively. For the reaction 3 CaO +2 Al 3 Ca + Al _ 2 O _ 3 the standard reaction enthalpy _ r H ^ 0= .......... kJ. (Round off to the Nearest Integer).

The standard enthalpies of formation of Al _ 2 O _ 3 and CaO are …

MCQ

The standard enthalpies of formation of $Al _{2} O _{3}$ and $CaO$ are $-1675\, kJ\, mol ^{-1}$ and $-635\, kJ\, mol ^{-1}$ respectively.

For the reaction $3 CaO +2 Al \rightarrow 3 Ca + Al _{2} O _{3}$ the standard reaction enthalpy $\Delta_{ r } H ^{0=}$ .......... $kJ$.

(Round off to the Nearest Integer).

✓

Correct option: C.

$230$

c
Given reaction:

$3 CaO + Al \rightarrow Al _{2} O _{3}+3 Ca$

Now, $\Delta_{ r } H ^{\circ}=\Sigma \Delta_{ f } H _{\text {Products }}^{\circ}-\Sigma \Delta_{ f } H _{\text {Reactants }}^{\circ}$

$=[1 \times(-1675)+3 \times 0]-[3 \times(-635)+2 \times 0]$

$=+230 kJ mol ^{-1}$

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$Zn\left( s \right) + C{u^{2 + }}\left( {aq} \right) \rightleftharpoons Z{n^{2 + }}\left( {aq} \right) + Cu\left( s \right)$

Standard reaction enthalpy $\left( {{\Delta _r}{H^ - }} \right)$ ....... $\mathrm{kJ}$