calcute the amoutnt tobe weighed 100ml of a 2mmol/L solution(Mw=136g), pH7,4?

Question

how to work out in the lab to prepare a solutin of potacium dihygen phosphate 100ml, 2mmol/L , (Molecular weigh=136g) ,pH= 7,4

Answer 1

I presume you mean you wish to make 100 ml of 2 mole / L solution of KH2PO4.

first determine the # of mmoles of KH2PO4 needed -

100 ml x 2 mmole/ml = 200 mmole

second determine the mg / mmole of KH2PO4 which you claim is 136 mg / mmole and I am not going to check for you

Now
200 mmole x 136 mg / mmole = mg HK2PO4 - you can do the math