You wish to prepare 220 grams of 21.2 % FeCl,.

You will need

grams of iron (II) chloride

mL of water.

and

Assume that the density of water is 1.00 g/ml

You will need 46.6 grams of iron (II) chloride and 173 mL of water.

Explanation:

x = mass of FeCl₂, y = mass of water

Assuming the percentage is by weight, we can write two equations:

x / (x + y) = 0.212

x + y = 220

Solving the system of equations:

x / 220 = 0.212

x ≈ 46.6

y ≈ 173

You will need 46.6 grams of iron (II) chloride and 173 mL of water.