help! i am totally stucked- osmolarity!

[soconfused]

Hello everybody!

 

This is one of the biggest challenges I have ever faced I hope that you have dealt with this matter before and hope that you can give me some advice and help.

Thanks very much in advance!

 

the recipe:

 

Sodium phosphate: Each ml contains 276mg of monobasic Naphos (NaH2PO4), and 142mg of dibasic naphos (Na2HPO4). 93 mg of phosphorus/ml = 3 mmol. 92 mg of sodium per ml/23 = 4 meq/ml. Osmolarity: 7000 mOsm/L

 

my problems:

 

a) as the recipe states 1 ml solution contains 276mg of monobasic Naphos (NaH2PO4), and 142mg of dibasic naphos (Na2HPO4). then how come they only get 93 mg of phosphorus/ml = 3 mmol?????

It seems like we are dealing with a buffer ( NaH2PO4 and Na2HPO4).

 

b) again, how come they only get 92 mg of sodium per ml/23 = 4 meq/ml???

 

c) how many particles do i have in this solution?

 

My point:

NaH2PO4 -> Na+ + H2PO4-

I am not sure if the dissociation stops here or if H2PO4- will dissociate more and give more particles????

 

 

Na2HPO4-> 2Na+ + HPO4(2-)

like the above, will H2PO4- dissociate more and give more particles????

 

then what is the total number of particles we have in solution? How can you calculate the osmolarity when you have the combination of NaH2PO4 and Na2HPO4?

 

 

hope very much for advices!

 

thanks alot!