Question

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

Answer 1

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

Explanation:

`"Osmolarity"` refers to the number of solute ions in solution. A `1.0*mol*L^-1` concentration of sodium chloride is `"2 osmolar"`, because sodium chloride speciates in aqueous solution to stoichiometric `Na^+(aq)` and `Cl^(-)(aq)` ions.

Upon dissolution, `"cupric bromide"` gives three equiv of ions:

`CuBr_2(s) + "excess "H_2O(l) rarr Cu^(2+)(aq)+2Br^(-)(aq)`

And thus `1.00*mol*L^-1` `CuBr_2(aq)` is `"3.00 osmolar"`.

On the other hand, a `0.30` `"osmolar"` solution of saline, has a concentration of `0.15*mol*L^-1` with respect to sodium chloride. Clearly, the solution of the copper salt is more concentrated, and expresses a greater osmolarity.