Question

Using oxidation numbers, explain why this reaction is not a redox reaction?
CaCo3 --------> CaO + Co2
Please help.

Answer 1

Assign oxidation numbers to each atom on each side and notice that the oxidation number does not change; i.e., Ca is +2 on the left and +2 on the right. Here is a good site to show how to determine oxidation numbers. Post if you still have questions but tell exactly what your problem is.
http://www.chemteam.info/Redox/Redox-Rules.html