Question

For the following reaction show all work:

1. Give the oxidation number for each element in the following equation.

Fe2O3 (s) + CO (g) = Fe (s) + CO2 (g)

a. Write the balanced oxidation half reaction.

b. Write the balanced reduction half reaction.

c. What is the oxidizing agent?

d. What is the reducing agent?

e. What is the net ionic equation?

Answer 1

1)

Fe2O3 (s) + CO (g) -> Fe (s) + CO2 (g)

Fe2O3: Fe +3 andO -2

CO: C +2 and O -2

Fe : Fe0

CO2: C +4 and O-2

a) Oxidation half reaction

C +2 ? C+4 + 2 e-

b)

3 e- + Fe+3 ? Fe

c)

Oxidizing agent: the one that is reduced, in this case is Fe+3, so choose Fe2O3 as the oxidizing agent. You should also add CO, see why in the next question d)

d)

NOTE: Because there is only one reactant in the third reaction, it is different from the other two. Some of the carbon atoms in CO(g) are oxidized from +2 to +4, and some of them are reduced from +2 to 0.

Thus carbon atoms in CO are both oxidized and reduced, and CO is both the oxidizing agent and the reducing agent.

e)

Balance oxydation and reduction equations:

2(3 e- + Fe+3 ? Fe)

6 e- + 2 Fe+3 ?2 Fe

6 e- + Fe2O3 ?2 Fe

and now:

3(C+2 ? C+4 + 2 e- )

3 C+2 ?3 C+4 + 6 e-

3CO ? 3 CO2 + 6 e-

As you can see, now electrons are balanced

Fe2O3 + 3 CO ? 2 Fe + 3 CO2

NOTE that this equation is balanced both in electrons and in atoms