How much NaCl do I need to fill a 3L bottle with a solution that is twice the osmolarity of plasma?

Question

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Answer 1

Ok, well lets take normal plasma osmolarity as 290 mOsm. That means that you would need a 580 mOsm solution of NaCl. Since NaCl forms 2 ions, Na+, and Cl-, you would need 290 mM of NaCl, or 290 mmol/L. To fill a 3L bottle, you would need 3 times this amount, or 870 mmol of NaCl, which is 0.870 mol. NaCl has a molar mass of 58.4, so you would need (0.870 mol x 58.4 g/mol) = 50.8 g of NaCl in 3L of water, to have twice the osmolarity of plasma.