# How Do You Calculate Osmolarity?

Osmolarity of 0.3% sodium chloride solution
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The correct answer is E. Assuming all solutes are impermeable, that is.  All have an osmolarity of 4. To calculate osmolarity you simply multiply the number of solutes (in the this case b and c dissociate in to 4 and 2 solutes respectively) by the Molarity.
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4.0M glucose
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I have the following solution which is 100 ml volume
paracetamol 1 g
disoduim phosphate dihydrate 150 mg
l-cysteine HCL H2O 30 mg
soduim metabisulphate 100 mg
iwant to use mannitol to balance the osmolarity
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Osmolarity is a measure of the osmotic pressure exerted by a solution around a perfect semi-permeable membrane and is compared to pure water. 1 mole of glucose dissolved in 1 litre of water has an osmolarity of 1 osmole. That means 4 om glucose has osmolarity of 4.
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Anonymous commented
Answer is E) Osmolarity formula is M x number of particles formed from one molecule e.g.,
NaCL: 2M x 2 = 4 M (NaCl--2 particles -- 1 Na and 1 Cl) another Na3PO4 is 1M x 4 = 4
3 particles for Na and 1 particle for PO4 ..hope this helps..rambo
Anonymous commented
Can you explain why the osmolarity of 5% dextrose in a liter of water is 255 as appeared on the label whereas my computation based on the following reasoning yields 278 mOsm/L instead?

5% dextrose = 50 gm/L of dextrose
gm MW of c6H12O6 = 180 gm/Mol
Therefore 50 gm = 0.278 Mol
Osm = g x Mol/L = 1 osm/Mol x 0.278 Mol/L = 0.278 osm/L or 278 mOsm/L 