Pharmacy Math
posted by Fai on .
A prescription calls for 250ml of a 0.1N hydrochloric acid HCL solution. How many ml of concentrated hydrochloric acid are needed to make this solution? The specific gravity hydrochloric acid is 1.18 the molecular weight is 36.46 and the concentration is 37.5% because hydrochloric acid function as an acid and react giving up one proton in a chemical reaction, 1 Eq is contained in each mole the compound. This the equivalent weight is 36.46g.
My calculation:
250ml x 0.1N changes 0.25L x 0.1 = 0.025meq.
0.025 x 36.46 = 0.9115gm
Thus 1gm of pure HCL is contained 100gm/37.5 = 2.66gm
And then 0.9115 x 2.6gm /1.18 = 2.01gm
Who tells me the right answer. My own answer is 2.01gm. Please helps me.

The problem asks for mL of the concentrated acid; you calculated grams.
N acid = 1.18 x 1000 x 0.375 x (1/36.46) = about 12.14 N
Then 12.14 x ?mL = 250 x 0.1
Solve for ?mL. I obtained 2.06 mL which corresponds to 2.06*1.18 = 2.43 g.