# Question #2eec6

Oct 19, 2017

$\text{0.36292 moles}$

#### Explanation:

For starters, you already know that $1$ mole of rubidium has a mass of $\text{85.4678 g}$ because rubidium has a molar mass of ${\text{85.4678 g mol}}^{- 1}$.

So if you know the mass of $1$ mole of rubidium, you can use it as a conversion factor to figure out the number of moles needed to have $\text{31.018 g}$.

$31.018 \textcolor{red}{\cancel{\textcolor{b l a c k}{\text{g"))) * "1 mole Rb"/(85.4678color(red)(cancel(color(black)("g")))) = color(darkgreen)(ul(color(black)("0.36292 moles Rb}}}}$

The answer must be rounded to five sig figs, the number of sig figs you have for the mass of rubidium.