# When would you know to use the Avogadro number as a conversion factor in a stoichiometry problem?

May 22, 2017

You might have to restate your question........

#### Explanation:

Well, first you have to write a stoichiometric equation that represents the chemical reaction.....

And then you have to work out the molar equivalence. Which reagent is in excess; which reagent is in deficiency?

When we use the atomic masses printed on the Periodic Table, and we use these masses all the time, the given mass IN GRAMS is equal to $\text{Avogadro's Number}$ of that atom.

And should I burn $12 \cdot g$ of carbon in stoichiometric oxygen......

$C \left(s\right) + {O}_{2} \left(g\right) \rightarrow C {O}_{2} \left(g\right) \uparrow$

I require $32.0 \cdot g$ of oxygen gas, and I get $44.0$ of product gas.

Hang on, the atomic mass of oxygen is listed as $16.0 \cdot g \cdot m o {l}^{-} 1$. Why do I require $32.0 \cdot g$ ${O}_{2}$ for this reaction?