Question

A chemist prepares a solution by dissolving 0.3 mole of CaCl2 in enough water to make 1000 mL of solution. What is the molar concentration of chloride ions?

Answer 1

$CaCl_{2}$ dissolves in water to give $Ca^{2+}$ and $Cl^{-}$ ions according to the following reaction:

$CaCl_{2}$  -------->  $Ca^{2+}$  + 2$Cl^{-}$

So, according to the above reaction, 1 mole of $CaCl_{2}$ produce 2 moles of $Cl^{-}$ ion,

So, 0.3 mole will give = 0.3 x 2 = 0.6 moles of  $Cl^{-}$ ion

So, Molar concentration = $\frac{0.6moles}{1L} = 0.6$

Note: 1L = 1000mL