Question

What is the mole ratio of `CO(g)` to `CO_2(g)` in the reaction `2CO(g) + O_2(g) -> 2CO_2(g)`?

Answer 1

`1:1`

Explanation:

The mole ratio that exists between two chemical species that take part in a chemical reaction is simply the ratio that exists between the stoichiometric coefficients added in front of said species.

In your case, you have

`color(blue)(2)"CO"_ ((g)) + "O"_ (2(g)) -> color(red)(2)"CO"_ (2(g))`

According to the balanced chemical equation that describes this reaction, the reaction consumes `color(blue)(2)` moles of carbon monoxide and `1` mole of oxygen gas and produces `color(red)(2)` moles of carbon dioxide.

So, carbon monoxide has a coefficient of `color(blue)(2)`. The same can be said about carbon dioxide, which has a coefficient of `color(red)(2)` as well.

This means that the mole ratio that exists between carbon monoxide and carbon dioxide will be

`(color(blue)(2)color(white)(.)"moles CO")/(color(red)(2)color(white)(.)"moles CO"_2) = color(blue)(2)/color(red)(2) = 1/1`

Because the two coefficients are equal, we say that the two compounds have a `1:1` mole ratio.