Question

What is the osmolarity of each of the following solutions?

2.0 M KNO₃

2.0 M Na₂SO₄

2.0 M in both KNO₃ and NaCl

2.0 M in both KNO₃ glucose

Answer 1

Osmolarity = i*Molarity

i is number of particles the solute dissociates into

1)

i for KNO3 is 2 because it dissociates into 1 K+ and 1 NO3-

Use:

Osmolarity = i*Molarity

= i*2.0 M

= 4.0 osM

Answer: 4.0 osM

2)

i for Na2SO4 is 3 because it dissociates into 2 Na+ and 1 SO42-

Use:

Osmolarity = i*Molarity

= 3*2.0 M

= 6.0 osM

Answer: 6.0 osM

3)

i for KNO3 = 2

i for NaCl = 2

so, i total = 4

Use:

Osmolarity = i*Molarity

= 4*2.0 M

= 8.0 osM

Answer: 8.0 osM

4)

i = 1 for glucose because it is non electrolyte

i for KNO3 = 2

so, i total = 3

Use:

Osmolarity = i*Molarity

= 3*2.0 M

= 6.0 osM

Answer: 6.0 osM