Question

What are the respective concentrations (M) of Cu2+ and Cl- afforded by dissolving 2.0 g CuCl2 in water and diluting to 500 mL.

Answer 1

First, the concentration of CuCl₂ itself should be determined:

$[CuCl_2]=\frac{\frac{2.0g}{134.45g/mol}}{0.500L}=0.030M$

In aqueous solution CuCl₂ dissociates according to the equation:

CuCl₂ --> Cu²⁺ + 2Cl^-

Evidently, the concentration of Cu²⁺ is equal, and the concentration of Cl^- is twice the concentration of CuCl₂.

Therefore, $[Cu^{2+}]=0.030M;$

$[Cl^-]=0.030\times2=0.060M$

Answer: [Cu²⁺] = 0.030 M; [Cl^-] = 0.060 M (or 1 : 2).