Question

The overall reaction in a commercial heat pack can be representedas shown below.

Answer 1

Explanation:

$4 Fe(s) + 3O_2(g)\rightarrow 2Fe_2O_3(s) ,\Delta H = -1652 kJ$

a) Heat released when 4.48 moles of iron is reacted with excessive oxygen:

According to reaction, when 4 moles of an iron reacts with 3 moles of oxygen it gives 1625 kilo Joules of heat.

Then 4.48 moles of iron will give:

$\frac{1652 kJ}{4}\times 4.48=1850.24 kJ$

1850.24 kJ of heat is released when 4.48 moles of an iron is reacted with excess oxygen.

b) Heat released when 1.76 mol $Fe_2O_3$ is produced.

According to reaction, when 2 moles of an $Fe_2O_3$ are produced 1625 kilo Joules of heat is released

Then heat released on production of 1.76 mol $Fe_2O_3$ :

$\frac{1652 kJ}{2}\times 1.76=1453.76 kJ$

1453.76 kJ heat is released when 1.76 mol $Fe_2O_3$ is produced.

c) Heat released when 2.66 grams of iron is reacted with excessive oxygen:

Moles of iron = $\frac{2.66 g}{56 g/mol}=0.0475 mol$

According to reaction, when 4 moles of an iron reacts with 3 moles of oxygen it gives 1625 kilo Joules of heat.

Then 0.0475 moles of iron will give:

$\frac{1652 kJ}{4}\times 0.0475=19.62 kJ$

19.62 kJ of heat is released when 2.66 grams of iron is reacted with excessive oxygen.

d) Heat released when 12.8 g Fe and 1.49 g oxygen gas are reacted:

Moles of iron = $\frac{12.8 g}{56 g/mol}=0.2286 mol$

According to reaction, 4 moles of iron reacts with 3 moles of oxygen.Then 0.2286 mol will react with:

$\frac{3}{4}\times 0.2286 mol=0.17145 mol$ of oxygen

Moles of oxygen = $\frac{1.49 g}{56 g/mol}=0.04656 mol$

According to reaction, 3  moles of oxygen gas reacts with 4 moles of iron .Then 0.04656 mol will react with:

$\frac{4}{3}\times 0.04656 mol=0.06208 mol$ of iron.

From this we can conclude that oxygen is in limiting amount. So, the amount of energy release will depend upon moles of oxygen gas.

According to reaction, when 4 moles of an iron reacts with 3 moles of oxygen it gives 1625 kilo Joules of heat.

Then 0.04656 moles of oxygen gas will give:

$\frac{1652 kJ}{3}\times 0.04656 =25.7011 kJ$

25.7011 kJ of Heat is released when 12.8 g Fe and 1.49 g oxygen gas are reacted