# How many molecules are present in a 20*g mass of "carbon dioxide"?

Sep 27, 2016

Approx. $3.0 \times {10}^{23} \text{ carbon dioxide molecules}$
$\text{Avogadro's number}$ $=$ $6.022 \times {10}^{23} \cdot m o {l}^{-} 1$.
Now, in $44 \cdot g$ of gas there are $\text{Avogadro's number}$ of molecules by definition.
And thus $6.022 \times {10}^{23} \cdot m o {l}^{-} 1$ $\times$ $\frac{20 \cdot g}{44.0 \cdot g \cdot m o {l}^{-} 1}$ $\cong$ $3.0 \times {10}^{23} \text{ carbon dioxide molecules}$. You can make a better estimate.