Finding coefficients in redox equation

Question

in the balanced equation for the following redox equation, the sum of the coefficients is ___?

 

Fe^3+ +I- = Fe^2+ + I2

 

a. 4 

b. 5

c. 6

d. 7

e. 8

 

Answer 1

Fe³⁺ +I^- = Fe²⁺ + I_²

 

Assign oxidation numbers to each.

+3     -1      +2      0

 

Clearly, it can be seen that Fe³⁺ is reduced while I^- is oxidized.

 

Write the oxidation half reaction and balance.

2I- → I₂ + 2e-

 

Write the reduction half reaction and balance.

Fe³⁺ + e- → Fe²⁺

 

The number of electrons in both must be the same. This means that we must multiply the second equation by 2 to achieve this. i.e.

 

2Fe³⁺ + 2e^- → 2Fe²⁺

 

Add the two balanced half reactions in which the number of electrons are the same.

 

2Fe³⁺ + 2e-  + 2I- → 2Fe²⁺ + I₂ + 2e- 

 

Cross out the number of electrons on both sides.

 

2Fe³⁺ +  2I- → 2Fe²⁺ + I₂ 

 

I leave the last part for you to do. What is the sum of the coefficients?