# What is the "molar concentration" of a mass of 21.9*g mass of "potassium chloride" dissolved in 869*mL of solution?

$\text{Molarity}$ $=$ $\text{Moles of solute"/"Volume of solution}$
And so we just have to plug the given numbers in, knowing that $\text{potassium chloride}$ has a molar mass of $74.55 \cdot g \cdot m o {l}^{-} 1$.
$\text{Molarity}$ $=$ $\frac{\frac{21.9 \cdot g}{74.55 \cdot g \cdot m o {l}^{-} 1}}{0.869 \cdot L} \cong 0.3 \cdot m o l \cdot {L}^{-} 1$.
Note that $1 \cdot m L = {10}^{-} 3 L$; equivalently, $1000 \cdot m L \equiv 1.000 \cdot L$. What are the concentrations with respect to ${K}^{+} \left(a q\right)$ and $C {l}^{-} \left(a q\right)$?