How many molecules of Cl - are in 410mL solution to. 72 M CaCl2 (aq) ?

First we calculate the moles of CaCl₂

moles = concentration (M) x volume (dm³)

moles = 0.72 x 0.41

= 0.2952

Each mole of CaCl₂ releases 2 moles of Cl-

moles of Cl - = 0.2952 x 2

= 0.5904

Each mole contains 6.02 x 10²³ molecules. Total molecules:

0.5904 x 6.02 x 10²³

= 3.55 x 10²³ Cl - ions