Iron is oxidized to iron(III) oxide according to 4 ,Fe(s)+3 ,O_2(g) ; ;2 ,Fe_2O_3(s)…

CHEMISTRY · Multi-part · A Level · Chemistry · Energetics · Energetics

Problem

Iron is oxidized to iron(III) oxide according to

\mathrm{4\,Fe(s)+3\,O_2(g)\;\longrightarrow\;2\,Fe_2O_3(s)}

with an enthalpy change of

\Delta H=-825\,\text{kJ\,mol}^{-1}

referenced to one mole of

\mathrm{Fe_2O_3}

produced. An endothermic industrial step elsewhere in the plant requires a steady supply of

5.00\times10^{5}\,\text{kJ}

of thermal energy. Management intends to obtain this energy by completely oxidizing metallic iron that is

95.0\%

pure by mass (the remainder is inert slag). (a) Calculate the number of moles of

\mathrm{Fe_2O_3}

that must form to provide the required

5.00\times10^{5}\,\text{kJ}

of thermal energy. (b) Determine the corresponding number of moles of metallic iron that must react. (c) Compute the minimum mass of the

95.0\%

pure iron sample that must be supplied to the reactor in order to deliver the thermal energy requirement. (d) The process engineer assumes that oxygen is present in large excess and therefore does not limit the reaction. Justify, using stoichiometric reasoning, why this assumption permits the calculation carried out in parts (a)–(c).

Related theory

Browse the problem library