# Calcuting osmolarity

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Iliana Calcuting osmolarity

Hallo out there!

Could somebody please help me to understand how to calculate the osmolarity of a buffer?
More precise for the following buffer :

120mM NaCl
0.5mM CaCl2
2.5mM KCl
1.0mM MgCl2
10mM Glucose

Thank you in advance,
Iliana

The FFM The osmolarity of a solution

The osmolarity of a solution may be given as the sum of (yi)(ni)(Ci), where yi is the osmotic coefficient of solute i, n is the number of particles that solute i dissociates into and Ci is the molarity of solute i.

The osmotic coefficient (yi) has a range of 0 to 1 - the osmotic coefficient will be 1 when the solute is completely dissolved and 0 when insoluble.

so the osmolarity of your solution should be

2 x 120 (NaCl) + 3 x 0.5 (CaCl2) + 2 x 2.5 (KCl) + 3 x 1 (MgCl2) + 1 x 10 (Glucose) = 259.5 mOsm/L

Red text corrected typo on original post as stated below

Sami Tuomivaara TheFFM,

TheFFM,

A small correction, the osmolarity is 259.5 mOsm/L.

Cheers,

The FFM Indeed ... Good typo spot

Indeed ... Good typo spot

I will correct the original reply