Question

bottle of hcl which is 40 mass%and has density of 1.20g /ml. calculate ml to be taken from this bottle to prepare 500 ml solution of 0.2 M

Answer 1

First, determine the molarity of the solution of HCl and
Second, use the dilution formula.

1.20 g/mL x 1000 mL x 0.40 x (1 mol/36.5g) = 13.15 which I would round to 13.2 M
Then c1v1 = c2v2
13.2*v1 = 0.2M x 500 mL
Solve for v1.

You can do the M of the initial HCl solution another way.
40% by mass means 40g HCl/100 g solution.
40 g is how many mols? That's mols = grams/molar mass = 40/36.5 = 1.096 mols in 100 g solution. What's the volume of the solution (the 100g?). That's mass = volume x density or volume = mass/density = 100g/1.20 = 83.33 mL or 0.08333 L, so M = mols/L = 1.096/0.083333 = 13.15 which rounds to 13.2,

Answer 2

wrong question