Question

A cell has a concentration of non-permeable solutes of 310 mOsmoles/liter. Molecular weights are : NaCl = 58, Glucose= 180, Urea=60. Cell membranes are not permeable to NaCl and glucose, but are permeable to urea.

1. what % solution of glucose is isotonic, and what % solution of urea would be isosomotic with the isotonic glucose solution?

Answer 1

Given concentration is 310 mOs moles / L

That means 1 L contains 310 mOsmoles = 310x10^-3 Osmoles of glucose

1000 mL contains 310x10^-3 Osmoles of glucose

100 mL contains 310x10^-4 Osmoles of glucose

So mass of glucose , m = Number of moles x molar mass

= 310x10^-4 Osmoles x 180 (g/mol)

= 5.58 g

So Percent of glucose is 5.58%

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Given concentration is 310 mOs moles / L

That means 1 L contains 310 mOsmoles = 310x10^-3 Osmoles of urea

1000 mL contains 310x10^-3 Osmoles of urea

100 mL contains 310x10^-4 Osmoles of urea

So mass of urea , m = Number of moles x molar mass

= 310x10^-4 Osmoles x 60 (g/mol)

= 1.86 g

So Percent of glucose is 1.86%