Chapter 10, Problem 81AP

Interpretation Introduction

(a)

Interpretation:

Amount of heat released should be calculated when $4$ moles of $\text{Fe}$ reacts with excess oxygen.

Concept Introduction:

Combustion of iron is an exothermic process that is heat is released in the chemical reaction.

Answer to Problem 81AP

Amount of heat released = $\text{1652 kJ}$.

Explanation of Solution

${\text{4Fe(s)+3O}}_{\text{2}}\text{(g)}\stackrel{}{\to }{\text{2Fe}}_{\text{2}}{\text{O}}_{\text{3}}\text{(s) }\text{Δ}\text{H=-1652 kJ}$

As per the given balanced reaction, 4 moles of iron reacts with 3 moles of oxygen producing $\text{1652 kJ}$ heat and thus, the amount of heat released is equal to $\text{1652 kJ}$.

Interpretation Introduction

(b)

Interpretation:

Amount of heat released should be calculated when 1 mol of ${\text{Fe}}_{\text{2}}{\text{O}}_{\text{3}}$ is produced.

Concept Introduction:

Production of ${\text{Fe}}_{\text{2}}{\text{O}}_{\text{3}}$ from iron and oxygen is an exothermic process that is heat is released in the chemical reaction.

Answer to Problem 81AP

Amount of heat released = $\text{826 kJ}$.

Explanation of Solution

${\text{4Fe(s)+3O}}_{\text{2}}\text{(g)}\stackrel{}{\to }{\text{2Fe}}_{\text{2}}{\text{O}}_{\text{3}}\text{(s) }\text{Δ}\text{H=-1652 kJ}$

As per the given balanced reaction, production of 2 moles of ${\text{Fe}}_{\text{2}}{\text{O}}_{\text{3}}$ releases $\text{1652 kJ}$ heat.

Thus, for one mole of ${\text{Fe}}_{\text{2}}{\text{O}}_{\text{3}}$ production will release half of the heat energy as released by production of 2 moles of ${\text{Fe}}_{\text{2}}{\text{O}}_{\text{3}}$.

Hence, amount of heat released is $\frac{1652}{2}\text{kJ}=\text{826 kJ}$.

Interpretation Introduction

(c)

Interpretation:

Amount of heat energy released for $\text{1 g}$ of iron is reacted with excess oxygen should be calculated.

Concept Introduction:

Burning of iron in presence of oxygen is an exothermic reaction that is heat is released in the chemical reaction.

Answer to Problem 81AP

When 1 gm iron is reacted amount of heat produced is $\text{7}\text{.375 kJ}$.

Explanation of Solution

${\text{4Fe(s)+3O}}_{\text{2}}\text{(g)}\stackrel{}{\to }{\text{2Fe}}_{\text{2}}{\text{O}}_{\text{3}}\text{(s) }\text{Δ}\text{H=-1652 kJ}$

As per the given reaction,

$\text{4×56 g}$

$\text{F}\text{e}$ produces $\text{1652 kJ}$ heat

So, $\text{1 g}$

$\text{F}\text{e}$ produces $\frac{1652}{4\times 56}$

$\text{kJ}$ heat $=\frac{1652}{224}$

$\mathrm{kJ}$ heat $=7.375$

$\text{kJ}$ heat

Interpretation Introduction

(d)

Interpretation:

Amount of heat energy released when $\text{10 g}$

$\text{F}\text{e}$ and $\text{2 g }$

${\text{O}}_{\text{2}}$ reacts should be calculated.

Concept Introduction:

Limiting reagent should be calculated which will determine the heat energy release. Limiting reagent is defined as the reagent which is completely consumed in the reaction.

Answer to Problem 81AP

$\text{34}\text{.41 kJ}$ heat energy will be released when $\text{2 g}$

${\text{O}}_{\text{2}}$ reacts with $\text{10 g}$

$\text{Fe}$.

Explanation of Solution

$96\text{g}$ ${\text{O}}_2$ reacts with $\text{224 g}$ $\text{F}\text{e}$

$\text{1 g}$ ${\text{O}}_2$ reacts with $\frac{224}{96}\text{ g Fe}$

$2\text{g}$ ${\text{O}}_2$ reacts with $\frac{\text{224×2}}{\text{96 g Fe}}\text{=}\frac{\text{448}}{\text{96}}\text{g Fe=4}\text{.67 g Fe}$

Thus, ${\text{O}}_2$ is the limiting reagent.

Now, $96\text{g}$

${\text{O}}_2$ produces $\text{1652 kJ}$ heat

$\text{1 g}$ ${\text{O}}_2$ produces $\frac{\text{1652}}{\text{96 kJ}}$ heat

$2\text{g}$ ${\text{O}}_2$ produces $\frac{\text{1652×2}}{\text{96 kJ}}$ heat $\text{=34}\text{.41 kJ}$ heat