# In a 1*mg mass of oxygen gas what is the number of "oxygen atoms"?

Feb 4, 2017

#### Answer:

Approx, $4 \times {10}^{19}$ $\text{individual oxygen atoms........}$

#### Explanation:

We calculate the quotient: $\text{Mass"/"Molar mass}$, and get an answer in moles.

And thus $\text{moles of dioxygen} = \frac{1 \times {10}^{-} 3 \cdot g}{32.0 \cdot g \cdot m o {l}^{-} 1} = 3.1 \times {10}^{-} 5 \cdot m o l$.

Now it is fact that $\text{1 mole of stuff}$ contains, by definition, $\text{Avogadro's number}$ $=$ $6.022 \times {10}^{23} \cdot m o {l}^{-} 1$.

And thus the "number of oxygen atoms"=2xx3.1xx10^-5*molxx6.022xx10^23*mol^-1=??

Why did I include the $2$ in that product?