How do you calculate moles of ions in solutions?

Calculate the number of moles of your solution, then use the of the ions to calculate the number of moles.

e.g. 5g MgCl2 dissolved in 250ml of water

1. Calculate of MgCl2 5g MgCl2 * 1mol/95.21g = 0.053mol MgCl2

0.053mol/.250L = 0.210M MgCl2

1. Calculate concentration of Ions (Mg2+ and Cl-)

Use formula Stoichiometry

1mol MgCl2 : 1mol Mg2+: 2ml Cl-

Mg2+ = 1(0.201M) = 0.201M Mg2+ Cl- = 2(0.201M) = 0.420M Cl-