Question

A 55.29-g sample of Ba(OH)2 is dissolved in enough water to make 1.20 L of solution. How many milliliters of this solution must be diluted with water in order to make 1.00 L of 0.100 M Ba(OH)2? (Ignore significant figures for this problem.)

Answer 1

mols Ba(OH)2 = grams/molar mass = approx 0.3 but you need to be more accurate.
M Ba(OH)2 = about 0.3/1.20L = approx 0.31 or so.
Then use c1v1 = c2v2
0.31 x v = 0.100 x 1.00
Solve for v.

Answer 2

512