Question

1-A solution contains 322 mg of Na+ ions per liter. How many milliosmoles are represented in the solution?

2- How many milliosmoles of sodium are represented in 1 liter of 3% hypertonic sodium chloride solution? Assume complete dissociation.

3- Calculate the osmolarity, in milliosmoles per milliliter, of a parenteral solution containing 2 mEq/mL of potassium acetate (KC2 H3 O2 —m.w. 98)

Answer 1

An osmol is 1 mol particles that contribute to the osmotic pressure of a solution.

For example : Nacl dissociates completely in water to form NA⁺ & Cl^- ions.

Thus each mole of Nacl becomes too osmoles in solution. One mol of Na⁺ & one mol of Cl^-.

Therefore A solution of 1 mol / L Nacl has asmolarity od 2 osmol / L

(1) Molar mass of Na⁺ = 23 g / mol

Therefore No. of mol of Na⁺ in 322 mg i.e 0.322 g Na⁺.

= 0.322 g / 23 g / mol = 0.014 mol / L

= 14 m mol / L [ because 1 mol = 10⁷ m mol ]

therefore 14 m mol Na+ are present in 1 L solution.