# Is a copper(II) bromide solution at 1.00*mol*L^-1 concentration HYPERTONIC with respect to NaCl(aq) at the SAME concentration?

Nov 26, 2016

The $\text{cupric bromide}$ is HYPERTONIC with respect to a $0.30$ $\text{osmolar}$ solution of saline. I assume that red blood cells have an osmolairty of $0.30$ $\text{osmolar}$ (this is not specified in the question.)

#### Explanation:

$\text{Osmolarity}$ refers to the number of solute ions in solution. A $1.0 \cdot m o l \cdot {L}^{-} 1$ concentration of sodium chloride is $\text{2 osmolar}$, because sodium chloride speciates in aqueous solution to stoichiometric $N {a}^{+} \left(a q\right)$ and $C {l}^{-} \left(a q\right)$ ions.

Upon dissolution, $\text{cupric bromide}$ gives three equiv of ions:

$C u B {r}_{2} \left(s\right) + \text{excess } {H}_{2} O \left(l\right) \rightarrow C {u}^{2 +} \left(a q\right) + 2 B {r}^{-} \left(a q\right)$

And thus $1.00 \cdot m o l \cdot {L}^{-} 1$ $C u B {r}_{2} \left(a q\right)$ is $\text{3.00 osmolar}$.

On the other hand, a $0.30$ $\text{osmolar}$ solution of saline, has a concentration of $0.15 \cdot m o l \cdot {L}^{-} 1$ with respect to sodium chloride. Clearly, the solution of the copper salt is more concentrated, and expresses a greater osmolarity.