Which is more hypertonic 1 M of glucose or 1 M of NaCl

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jerichorayel | College Teacher | (Level 2) Senior Educator

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In answering the comparative question we should relate first the ability of each molecules to move in a solution. One of the governing factors that affect the mobility of the molecules is the osmotic pressure. In the latter sense, it will affect which is more hypertonic.

The higher the osmotic pressure, the more hypertonic.

so we try to solve for the osmotic pressure for NaCL and glucose.


Osmotic pressure = icRT

where i = van't Hoff factor

c = concentration in molarity

R= gas constant; 0.08206atm-l/mole-K

T= temperature in kelvin


Since there is no temperature indicated, we will try to use 298K (or room temperature) for the both solutions.

for 1M glucose

Osmotic P = (1)(1mole/L) (0.08206atm-l/mole-K) (298K)

                = 24.45atm

**van't Hoff factor (i)=1 because glucose do not dissociate into ions when it is in the solution.



for 1M NaCl

Osmotic P = (2)(1mole/L) (0.08206atm-l/mole-K) (298K)

                = 24.45

                = 48.91 atm


**van't Hoff factor (i)=2 because NaCl dissociates into ions when it is in the solution. NaCl ---> Na+  + Cl-

We can simply picture it out as: there are more particles in 1M NaCl than in 1M glucose because of dissociation.


Therefore NaCl is more hypertonic.


Hope this helps :)