What is the mole ration of o2 to co2?

The mole ratio of O₂ to CO₂ depends on what the reactions is.
Overall speaking, the mole ratio of O₂ to CO₂ is equal to the ratio of coefficients in the equation for the reaction.

For example:
C + O₂ → CO₂
Mole ratio O₂ : CO₂ = 1 : 1

For example:
CH₄ + 2O₂ → CO₂ : 2H₂O
Mole ratio O₂ : CO₂ = 2 : 1

I do that sometimes, too, for some reason (write ration instead of ratio). Usually when I type fast.

If you are talking mole ratio of products and reactants, you will have as many moles of CO2 as you had of O2 (a 1 to 1 ratio), as long as all the original O2 got consumed (there was excess carbon). Does depend on the system you are talking about. There is not a 1:1 mole ratio of O2 to CO2 in the atmosphere. More like 500. (200,000 ppm O2 versus 400 ppm CO2).

a ratio you mean ?