Molarity help please!!!

Question

Calculate the molarity of a solution prepared by dissolving 3.45g LiBr in 250. mL solution.

Determine the final concentration of a solution if 15.0 mL of a 12.0 M solution is diluted to a final volume of 250. mL with water.

Thank you!

Answer 1

Molarity = grams / liters = 3.45 gm / .250 L = 13.8 M

Ci x Vi = Cd x Vd (i = initial; d = dilute)

Cd = Ci x Vi / Vd = 12 M x 15 ml / 250 ml = 180 / 250 = .72 M