# How many atoms of silicon are in 2.50 moles of SiO_2?

$2.50 \times {N}_{A}$, where ${N}_{A} = \text{Avogadro's number}$.
If I asked you $\text{how many silicon atoms there are in}$ $\text{two and a half DOZEN silicon dioxide units}$ I think you would be able to answer $\text{30}$ easily without thinking too much. Can you tell me how many oxygen atoms there are in that quantity?
This question asks you the same thing, but instead of using dozens as a unit of measure, it uses moles, where 1 mole of stuff numbers $6.022 \times {10}^{23}$ items of that stuff. Capisce?