The highly exothermic thermite reaction, in which aluminum reduces iron(III) oxide to elemental iron, has been used by railroad repair crews to weld rails together.
2Al(s) + Fe₂O₃(s) $\to$ 2Fe(s) + Al₂O₃(s) $\Delta$ H = -850 kJ
What mass of iron is formed when 725 kJ of heat are released?

Question

The highly exothermic thermite reaction, in which aluminum reduces iron(III) oxide to elemental iron, has been used by railroad repair crews to weld rails together.
2Al(s) + Fe₂O₃(s)

\to

2Fe(s) + Al₂O₃(s)

\Delta

H = -850 kJ
What mass of iron is formed when 725 kJ of heat are released?

Quizplus · Accepted Answer

The thermite reaction releases 850 kJ of heat for every 2 moles of Fe produced. To find the mass of Fe formed when 725 kJ of heat are released, use the ratio (725 kJ / 850 kJ) and multiply by the molar mass of 2 moles of Fe (2 x 55.85 g/mol = 111.7 g). This gives approximately 95 g of Fe.

The Highly Exothermic Thermite Reaction, in Which Aluminum Reduces Iron(III) →\to→

The Highly Exothermic Thermite Reaction, in Which Aluminum Reduces Iron(III) $\to$