# For a litre volume, what is the mass of calcium chloride present in a 2*mM solution of CaCl_2?

Sep 17, 2016

A stoichiometric quantity, approx. $222$ $m g$.

#### Explanation:

$\text{Molarity}$ $=$ $\text{Moles of solute"/"Volume of solution}$, and thus $\text{molarity}$ has units of $m o l \cdot {L}^{-} 1$. And thus,

$\text{Moles of solute"="Volume of solution"xx"molarity}$

We have a $2 \text{mM}$ solution, i.e. a $2.0 \times {10}^{-} 3 m o l \cdot {L}^{-} 1$ of $C a C {l}_{2}$, and, clearly, there are $2.0 \times {10}^{-} 3 m o l$ of $C a C {l}_{2}$ present in solution.

Thus, with respect to $C a C {l}_{2}$ there are ............

$1 \cdot \cancel{L} \times 2.0 \times {10}^{-} 3 \cancel{m o l \cdot {L}^{-} 1} \times 110.98 \cdot g \cdot \cancel{m o {l}^{-} 1}$ $=$ $0.222 \cdot g$ calcium chloride. What is the concentration of this solution with respect to $C {l}^{-}$ ion?