Problem:

Hydrochloric acid R1. 1043501. Contains 250 g/L of HCl. Dilute 70 g of hydrochloric acid R to 100 mL with water R.

How many ml of the concentrated HCl R (D = 1,19 g/mL; Ar= 36,45 g/mol; w(HCl) = 37 %) do we need to prepare 500 mL of hydrochloric acid R1?

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My calculations:

70 g of HCl R in 100ml solution -> 350 g of HCl R in 500ml solution

volume = mass/density -> 350g/1,19 g/ml -> 294 ml

However the correct answer is 284ml. Can anyone point out the mistake that I've made?