Chapter 19.2, Problem 15PP

Interpretation Introduction

Interpretation: The given redox reaction is to be balanced using the oxidation number method.

Concept Introduction :

The oxidation number method involves:-

• Assign the oxidation number to each element.
• Check which element is oxidized and which element is reduced.
• Check the change in oxidation number for the elements which are oxidized and reduced.
• Balance the change in oxidation number by adjusting the coefficients in the equation.
• Then balance the other elements.

Answer to Problem 15PP

  $3\text{H}\text{C}\text{l}+2\text{H}\text{N}{\text{O}}_3\to 3\text{H}\text{O}\text{C}\text{l}+2\text{N}\text{O}+{\text{H}}_2\text{O}$

Explanation of Solution

The given redox reaction is:

  $\text{H}\text{C}\text{l}+\text{H}\text{N}{\text{O}}_3\to \text{H}\text{O}\text{C}\text{l}+\text{N}\text{O}+{\text{H}}_2\text{O}$

Assigning the oxidation number-

  $\stackrel{+1}{\text{H}}\stackrel{-1}{\text{C}\text{l}}+\stackrel{+1}{\text{H}}\stackrel{+5}{\text{N}}{\stackrel{-2}{\text{O}}}_3\to \stackrel{+1}{\text{H}}\stackrel{-2}{\text{O}}\stackrel{+1}{\text{C}\text{l}}+\stackrel{+2}{\text{N}}\stackrel{-2}{\text{O}}+{\stackrel{+1}{\text{H}}}_2\stackrel{-2}{\text{O}}$

The oxidation numbers of atoms show that

$\text{C}\text{l}$ is oxidized and $\text{N}$ is reduced.

Change in oxidation number of $\text{C}\text{l}=+2$

Change in oxidation number of $\text{N}=-3$

Thus adjusting the coefficients:

  $3\text{H}\text{C}\text{l}+2\text{H}\text{N}{\text{O}}_3\to 3\text{H}\text{O}\text{C}\text{l}+2\text{N}\text{O}+{\text{H}}_2\text{O}$

Conclusion

Thus the balanced chemical equation is:

  $3\text{H}\text{C}\text{l}+2\text{H}\text{N}{\text{O}}_3\to 3\text{H}\text{O}\text{C}\text{l}+2\text{N}\text{O}+{\text{H}}_2\text{O}$