Question

Latanya brown is a nine-year old african american who is hospitalized with acute sickle cell crisis. the pharmacist is preparing intravenous fluids for this patient. she adds 2 grams of potassium chloride to 1 l of d5w/1/2 normal saline. what is the estimated osmolarity per liter (mosm/l) of this solution assuming the final volume is 1 l (mw of sodium

Answer 1

Potassium Chloride = KCl

KCl has a molar mass of: 39.0983g+35.4530g=74.5513g

The number of moles of KCL we are adding is: 2g/(74.5513g/mol) = 0.02683 mol

But you have to keep in mind that salts in water dissociate:

KCl -> K+ + Cl-

So 1 mole KCl is 2 osmoles (because it’s two particles)

So if you add 0.02683 moles, you are adding 0.02683*2 = 0.05366 osmoles. If you dissolve them in 1 liter, you have a solution 0.05366 OsM = 53.66 mOsM

D5W = dextrose 260 mOsM

1/2 Normal Saline = has half of the normal saline concentration - a normal saline solution has the same sodium chloride concentration as blood serum = 154 mOsm

You have to sum up all the osmolarities:

=  53.66 mOsM + 154 mOsM + 260 mOsM = 467.66 mOsM