# If you are given the amount of H_2O = 3.00 mol how can you find an unknown of mass of CO_2 in grams?

Mar 17, 2018

Well, you certainly cannot find it on the basis of the data you propose...

#### Explanation:

I ASSUME that you combust some hydrocarbon....i.e. say methane. Now all hydrocarbons completely combust to give carbon dioxide, and water, AND energy, which can be used for some purpose....

If you combusted METHANE....then we would write the combustion equation as follows...

$C {H}_{4} \left(g\right) + 2 {O}_{2} \left(g\right) \rightarrow C {O}_{2} \left(g\right) + 2 {H}_{2} O \left(l\right) + \Delta$

And so if combustion of this gas evolved $3.00 \cdot m o l$ of WATER, then CLEARLY, by the stoichiometry of the reaction, a molar quantity of $1.5 \cdot m o l$ with respect to methane must have been combusted....the which represents a mass of $1.5 \cdot m o l \times 15 \cdot g \cdot m o {l}^{-} 1$, approx. $23 \cdot g$. And with respect to carbon dioxide, then $1.5 \cdot m o l$ were evolved....

But we got no idea of the question you ask...