Chapter 8, Problem 24PE

(a)

Interpretation Introduction

Interpretation:

The given chemical reaction has to be interpreted in terms of number of moles of each reactant product.  The reaction has to be indicated as exothermic (or) endothermic.

The given chemical equation is,

  $\text{2}{\text{Na+Cl}}_{\text{2}}\stackrel{}{\to }\text{2NaCl+822}\text{kJ}$

Concept Introduction:

Endothermic reaction:  Those reactions that absorb heat energy from the surroundings are called as endothermic reactions.  The breakage of chemical bonds absorbs heat energy.

Example:  In the process of photosynthesis, carbon dioxide and water are converted to free oxygen and glucose by absorbing heat energy.

  $\text{6}{\text{CO}}_{\text{2}}\text{+6}{\text{H}}_{\text{2}}\text{O+2519}\text{kJ}\stackrel{}{\to }{\text{C}}_{\text{6}}{\text{H}}_{\text{12}}{\text{O}}_{\text{6}}{\text{+6O}}_{\text{2}}$

Exothermic reaction:  Those reactions that release heat energy to the surroundings are called as exothermic reactions.  The formation of chemical bonds, releases heat energy.

Example:  In the combination reaction of solid carbon and gaseous oxygen, formation of gaseous carbon dioxide takes place with the evolution of heat energy.

  $\text{C}\left(\text{s}\right){\text{+O}}_{\text{2}}\left(\text{g}\right)\stackrel{}{\to }{\text{CO}}_{\text{2}}\left(\text{g}\right)\text{+393}\text{kJ}$

(b)

Interpretation Introduction

Interpretation:

The given chemical reaction has to be interpreted in terms of number of moles of each reactant product.  The reaction has to be indicated as exothermic (or) endothermic.

The given chemical equation is,

  ${\text{PCl}}_{\text{5}}\text{+92}\text{.9}\text{kJ}\stackrel{}{\to }{\text{PCl}}_{\text{3}}{\text{+Cl}}_{\text{2}}$

Concept Introduction:

Refer to part (a).

(c)

Interpretation Introduction

The given chemical reaction has to be interpreted in terms of number of moles of each reactant product.  The reaction has to be indicated as exothermic (or) endothermic.

The given chemical equation is,

  $\text{S}\left(\text{s}\right)\text{+2CO}\left(\text{g}\right)\stackrel{}{\to }{\text{SO}}_{\text{2}}\left(\text{g}\right)\text{+2C}\left(\text{s}\right)\text{+76}\text{kJ}$

Concept Introduction:

Refer to part (a).