How many milliliters of concentrated hydrochloric acid solution (36.0% HCl by mass, density = 1.18 g/mL) are required to produce 20.0 L of a solution that has a pH of 2.13?

Answer 1

You need to have two pieces of information before applying the dilution formula.
1. You need to convert pH to M.
pH = -log(H^+)
2.13 = pH. I get (H^+) = approximately 0.007 but you need to do that more accurately.
2. You need to convert 36% HCl to molarity.
density = 1.18; therefore, 1000 mL has a mass of 1000 mL x 1.18 g/mL = 1180 grams
That is 36% HCl; thus, 0.36*1180 g = 425 g (approximate)
How many moles is that in the 1000 mL soln? It is 425g/molar mass HCl and that is the molarity.
Then mL x M = mL x M.

Answer 2

11.667

Answer 3

molarity of 36% HCl=11.667