Question

How many milligrams of histamine phosphate (C₅H₉N₃,2H₃PO₄, M.Wt.307) are required for the preparation of 40 mL of a solution containing histamine (C₅H₉N₃, M.Wt. 111) at a concentration such that when 5 mL of the solution is diluted to 80 mL with water, a solution is produced containing histamine at a concentration of 1 in 2,000? (0 decimal places)

i got 128mg when i answered this would love to know where i went wrong

Answer 1

1 in 2000 concentration of histamine means 1mg/2mL or 0.5mg/ml.

5ml of histamine containing solution is diluted to 80mL with water. Resulted solution is 80ml at the rate of 0.5mg/ml.

Total histamine in 80 ml of diluted solution= 80ml×0.5mg/ml

= 40mg./5ml ( each ml contains 8mg)

So that the 5ml of histamine solution contains 40mg.

If it is calculated for 40ml it is as below

= 40ml×8mg

=320mg

320mg of histamine is required to prepare 40ml solution when that 5ml is diluted 80ml containing 1:2000