Chapter 19.1, Problem 11SSC

Interpretation Introduction

Interpretation:

The reaction of iron metal with hydrobromic acid to form iron (III) bromide and hydrogen gas is to be written. Also change in oxidation number of the element is to be determined.

Concept introduction:

Oxidation involves loss of electrons and reduction involves gain of electrons.

The loss of electrons = change in oxidation number of the element that is oxidized

The gain of electrons = change in oxidation number of the element that is reduced

Answer to Problem 11SSC

The balanced redox reaction is:

$2Fe+6HBr\to 2FeB{r}_3+3H_2$

Change in oxidation number of iron (oxidized) = +3

Change in oxidation number of hydrogen (reduced) = -1

Explanation of Solution

Reaction with oxidation number is:

$2\stackrel{0}{Fe}+6\stackrel{+1}{H}\stackrel{-1}{Br}\to 2\stackrel{+3}{Fe}{\stackrel{-1}{Br}}_3+3{\stackrel{0}{H}}_2$

Therefore,

Change in oxidation number of iron which is oxidized=+3

Change in oxidation number of hydrogen which is reduced = -1

Conclusion

The balanced redox reaction is:

$2Fe+6HBr\to 2FeB{r}_3+3H_2$

Change in oxidation number of iron (oxidized) = +3

Change in oxidation number of hydrogen (reduced) = -1