Calculate the chloride ion (Cl−) concentration for a 0.424 M MgCl2 solution.

Answer 1

To find the ion concentration of a salt in solution, we are going to break the compound into pieces.

(Consult the periodic table for the charges of these ions if needed. Mg is a group 2 metal with a charge of +2 and Cl is a halogen with a charge of -1.)

MgCl2 is made out of: one Mg ion and 2 Cl ions

MgCl2 —> Mg2+ + 2Cl-

This means every time one mole of MgCl2 breaks apart, it releases one mole of Mg ions and 2 moles of Cl ions.

We know the concentration of MgCl2 is 0.424M and we can use mole ratios to get the concentration of Cl- ions.

0.424M MgCl2 * 2 moles of Cl-/1 mole MgCl2 = 0.848 M Cl-

As a shortcut, we released 2 Cl- ions every time we broke the salt, so Cl- has double the concentration of the original compound. Hope this helps!