How many kilojoules of heat will be released when exactly 1 mole of iron, Fe, is burned to form Fe₂O₃(s) at standard state conditions?

To evaluate the amount of heat released for exactly 1 mole of iron, we have to follow the below-mentioned steps.

\(\begin{array}{l}{\rm{Combustion reaction of Fe(s) to F}}{{\rm{e}}_{\rm{2}}}{{\rm{O}}_{\rm{3}}}{\rm{(s) is:}}\\{\rm{ 2Fe(s) + }}{\rm{ }}\frac{{\rm{3}}}{{\rm{2}}}{{\rm{O}}_{\rm{2}}}{\rm{(g)}} \to {\rm{F}}{{\rm{e}}_{\rm{2}}}{{\rm{O}}_{\rm{3}}}{\rm{(s)}}\\{\rm{Now, }}{\bf{\Delta }}{{\bf{{\rm H}}}^{\bf{^\circ }}}_{{\bf{reaction}}}{\bf{ = }}\sum {{\bf{\Delta }}{{\bf{{\rm H}}}^{\bf{^\circ }}}_{{\bf{product}}}{\bf{ - }}\sum {{\bf{\Delta }}{{\bf{{\rm H}}}^{\bf{^\circ }}}_{{\bf{reactant}}}} } \\{\rm{ \Delta }}{{\rm{{\rm H}}}^{\rm{^\circ }}}_{{\rm{reaction}}}{\rm{ = }}{\left( {{\rm{\Delta {\rm H}}}_{{\rm{formation}}}^{\rm{^\circ }}} \right)_{{\rm{F}}{{\rm{e}}_{\rm{2}}}{{\rm{O}}_{\rm{3}}}{\rm{(s)}}}}{\rm{ - }}\left( {{{\left( {{\rm{2 \times \Delta {\rm H}}}_{{\rm{formation}}}^{\rm{^\circ }}} \right)}_{{\rm{Fe(s)}}}}{\rm{ + }}{{\left( {\frac{{\rm{3}}}{{\rm{2}}}{\rm{ \times \Delta {\rm H}}}_{{\rm{formation}}}^{\rm{^\circ }}} \right)}_{{{\rm{O}}_{\rm{2}}}{\rm{(g)}}}}} \right)\\{\rm{ \Delta }}{{\rm{{\rm H}}}^{\rm{^\circ }}}_{{\rm{reaction}}}{\rm{ = ( - 824}}{\rm{.2 kJ mo}}{{\rm{l}}^{{\rm{ - 1}}}}{\rm{) - (0 + 0)}}\\{\rm{ \Delta }}{{\rm{{\rm H}}}^{\rm{^\circ }}}_{{\rm{reaction}}}{\rm{ = - 824}}{\rm{.2 kJ mo}}{{\rm{l}}^{{\rm{ - 1}}}}\end{array}\)

The amount of heat released in the above chemical reaction is 824.2 kJ.

We have already calculated the total amount of heat released in the combustion of iron.

\(\begin{array}{l}{\rm{Amount of heat released during the combustion, due to, 2 mole of Fe amount of energy released is 824}}{\rm{.2 kJ}}{\rm{.}}\\1{\rm{ mole of Fe will release }}\frac{{824.2{\rm{ KJ}}}}{2}{\rm{ = 412}}{\rm{.1 kJ of heat }}\end{array}\)

Hence, the amount of energy released when exactly 1 mole of Fe is burnt to produce \({\rm{F}}{{\rm{e}}_2}{{\rm{O}}_{\rm{3}}}{\rm{(s)}}\)is 412.1 kJ.