Question

What is the enthalpy change for the given reaction, if enthalpies of formation of $Al_2O_3$ and $Fe_2O_3$ are $-1670\, kj\, mol^{-1}$ and $-834 \,kj \,mol^{-1}$ respectively?
$Fe_{2}O_{3} + 2Al \to Al_{2}O_{3}+2Fe$

• A. $-836 \,kj\, mol^{-1}$
• B. $+ 836\,kj\, mol^{-1}$
• C. $- 424\,kj\, mol^{-1}$
• D. $+ 424\,kj\, mol^{-1}$

Answer 1

Answer: (A)

$\Delta H = \Sigma\,\Delta H_{P} - \Sigma\,\Delta H_{R}$
$= -1670 - \left(-834\right) = -836\, kj\, mol^{-1}$