Question

Choose one answer

A 400 mOsm/1 glucose solution is:

A) Hyposmotic to a 200 mM solution of KCl

B) isosmotic to a 600 mM solution of KCl

C) Isosmotic to a 0.18% solution of KCl

D) Hyperosmotic to a 200 mM solution of KCl

E) isomotic to a 200 mM solution of KCl.

Answer 1

Osmoles are the number of particle moles in solution. If the solute dissociate into n particles ( n ions) in solution then its osmoles = n x no. of moles. or Osm/L = n x moles/L

Given the glucose concentration in milli Osmoles / L as 400 mOsm/L

That is there are 400 milliOsmoles of glucose present in 1 L of the solution.

since glucose doesn't dissociate in solution its molar concentration and osmolar concentration are the same.

We know that KCl dissociates in to K⁺ and Cl^- ions [ 2 particles]

therefore 200 mM of KCl = 2 x 200 = 400 mOsm/L of KCl

Thus it is equal to 400 mOsm/L of glucose.

That means it is isosmatic with 400mOsm/L of glucose.

This option is given in option (E). Hence option (E) is the Answer.

Thus the Answer is option (E)

Let us check the other options:

it is given that it is hypoosmatic,in option (A) means less than 400 mOsm/L.

In option (D) it is given hyperosmatic to 200 mM KCl means greater than 400 mOSm/L

Hence option (A) and option (D) are not the Answer.

in option (B) it is given isosmatic to 600mM of KCl solution

600mM KCl solution = 2 x 600 mOsm/L = 1200 mOsm/L

This is not equal to 400 mOsm/L of glucose.

Hence option (B) cannot be the Answer.

In option (C) it is given isosmatic to 0.18% KCl solution

0.18% KCl solution means 0.18 g per 100 mL of solution

          Or 1.8 g per L

             1.8 / 54.5 moles/L

             = 0.033 moles/L

            = 33 mM

           = 2 x 33 = 66 mOsm / L

This is not equal to 400 mOsm / L of glucose

Hence option C cannot be the answer