Chapter 19.2, Problem 18PP

Interpretation Introduction

Interpretation:

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

Concept introduction:

Oxidation number method involve:-

• 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 18PP

$3SnC{l}_4+2Fe\to 3SnC{l}_2+2FeC{l}_3$

Explanation of Solution

The given redox reaction is:

$S{O}_2+B{r}_2+H_{2}O\to HBr+H_{2}S{O}_4$

Assigning the oxidation number-

$\stackrel{+4}{S}{\stackrel{-2}{O}}_2+{\stackrel{0}{Br}}_2+{\stackrel{+1}{H}}_2\stackrel{-2}{O}\to \stackrel{+1}{H}\stackrel{-1}{Br}+{\stackrel{+1}{H}}_2\stackrel{+6}{S}{\stackrel{-2}{O}}_4$

The oxidation numbers of atoms shows that

$S$ is oxidized and $Br$ is reduced.

Change in oxidation number of $S=+2$

Change in oxidation number per $Bratom=-2$

Thus adjusting the coefficients:

$S{O}_2+B{r}_2+H_{2}O\to 2HBr+H_{2}S{O}_4$

Balancing the remaining atoms:

$S{O}_2+B{r}_2+2H_{2}O\to 2HBr+H_{2}S{O}_4$

Conclusion

Thus the balanced redox equation is:

$S{O}_2+B{r}_2+2H_{2}O\to 2HBr+H_{2}S{O}_4$