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# Osmolarity

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### #1 samita

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Posted 18 January 2011 - 09:08 AM

This solution

160 NaCl
2.5 KCl
1 CaCl2
2 MgCl2
10 HEPES
10 Glucose

has an osmolarity of about 320, how to calculate it from the molarity of the ionc composition.

### #2 Inmost sun

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Posted 10 February 2011 - 12:24 PM

I think itīs more in the range of 350 mOsmol...

This solution

160 NaCl
2.5 KCl
1 CaCl2
2 MgCl2
10 HEPES
10 Glucose

has an osmolarity of about 320, how to calculate it from the molarity of the ionc composition.

### #3 bob1

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Posted 10 February 2011 - 05:23 PM

Think about it like this... 1 mole of NaCl goes into solution to form one mole of Na+ and one mole of Cl- = 2 Osmole... HEPES and glucose do not do this so the osmolarity is 1 for each mole dissolved.

Assuming your solution above is in millimoles/litre (you should always write solutions with concentration units)
160 mM NaCl = 320 mOsmole
2.5 mM KCl = 5 mOsmole... etc I am sure you get the picture.

BTW Inmost sun is correct...