# A student needs to make 5.00xx10^1 mL of a potassium carbonate solution with a concentration of 3.3000xx10^(-2) mol/L. What mass of potassium carbonate should they use to make the solution? (Answer to 3 s.d. in g)

May 24, 2017

We need a mass of $228 \cdot m g$ of $\text{potassium carbonate}$...........

#### Explanation:

We use the relationship $\text{Concentration"="Moles of solute"/"Volume of solution}$.

And thus $\text{moles of solute"="concentration"xx"volume} \ldots \ldots .$

So here...............

$\text{moles} = 50 \cdot m L \times {10}^{-} 3 L \cdot m {L}^{-} 1 \times 3.30 \times {10}^{-} 2 \cdot m o l \cdot {L}^{-} 1$

$= 1.65 \times {10}^{-} 3 \cdot m o l$.

Which represents a mass of ............................

$= 1.65 \times {10}^{-} 3 \cdot \cancel{m o l} \times 138.21 \cdot g \cdot \cancel{m o {l}^{-} 1} = 0.228 \cdot g$.