How many grams of cacl2 must be used to provide 0.252 moles of chloride ions?

Calcium chloride dissociates as follows:

CaCl₂(s) ⇄ Ca²⁺(aq) + 2Cl⁻(aq)

According to the dissociation equation, it can be seen that CaCl₂ and Cl⁻ ions have stoichiometric ratio:

n(CaCl₂) : n(Cl⁻) = 1 : 2

n(CaCl₂) = n(Cl⁻)/2

So, it is necessary 2 times more moles of calcium chloride for producing 1 mole of Cl⁻.

n(CaCl₂) = 0.252/2 = 0.126 mole

Finally, we can calculate the necessary mass of calcium chloride:

m(CaCl₂)  = n x M = 0.126 x 110.98 = 13.98 g of CaCl₂