Question

Find the molarity and molality given a 12.5% soloution of HCl of density 1.064g/ml. I'm confused how to use the percentage? I am assuing I use it to find the mass or moles but not sure how?

Answer 1

mass percent = 12.5%

density = 1.064 g.ml

molar mass = 36.5 g/mol

Molarity = mass % x density x 10 / molar mass

              = 12.5 x 1.064 x 10 / 36.5

               = 3.64 M

Molarity = 3.64 M

M = molarity

d = density

molality = 1000 M / 1000 x d - M x molar mass

             = 1000 x 3.64 / 1000 x 1.064 - 3.64 x 36.5

             = 3.91

molality = 3.91 m