Question

The heat of formation of Fe2O3(s) is –826.0 kJ/mol. Calculate the heat of the reaction 4Fe(s) + 3O2(g) → 2Fe2 O3(s) when a 53.99-g sample of iron is reacted.

Answer 1

Answer : The heat of the reaction is, 399.784 kJ

Explanation :

The given balanced chemical reaction is,

$4Fe(s)+3O_2(g)\rightarrow 2Fe_2O_3(s)$

First we have to calculate the moles of iron.

$\text{Moles of }Fe=\frac{\text{Mass of }Fe}{\text{Molar mass of }Fe}=\frac{53.99g}{55.8g/mole}=0.968moles$

Now we have to calculate the moles of $Fe_2O_3$

From the reaction we conclude that,

As, 4 moles of Fe react to give 2 moles of $Fe_2O_3$

So, 0.968 moles of Fe react to give $\frac{2}{4}\times 0.968=0.484$ moles of $Fe_2O_3$

Now we have to calculate the heat of the reaction.

As, 1 mole of $Fe_2O_3$ produce heat = 826.0 kJ

So, 0.484 mole of $Fe_2O_3$ produce heat = $0.484\times 826.0=399.784kJ$

Therefore, the heat of the reaction is, 399.784 kJ