Question

If one liter of water contains 2 moles of NaCl, and 2 moles of glucose, what is the approximate osmolarity of

the solution in Osmoles per liter?
a. 2
b. 4
c. 5
d. 6
e. 8

Answer 1

The osmolarity of the solution containing 2 moles of NaCl (which dissociates into 4 moles of ions) and 2 moles of glucose (which does not dissociate) is 6 Osmoles per liter.

Step-by-step explanation:

If one liter of water contains 2 moles of NaCl and 2 moles of glucose, the osmolarity of the solution needs to be calculated. It is important to keep in mind that NaCl dissociates into two ions (Na+ and Cl-), hence 2 moles of NaCl will produce 4 moles of particles. Glucose does not dissociate in solution, so 2 moles of glucose will yield 2 moles of particles. Therefore, the osmolarity is the sum of the individual osmolarities of NaCl and glucose particles.

For every mole of NaCl, we get 2 moles of particles:
NaCl → Na+ + Cl-
2 mol NaCl → 4 mol particles
2 mol Glucose → 2 mol particles

The total osmolarity is therefore 4 (from NaCl) + 2 (from glucose) = 6 Osmoles per liter.