Question

1.78% solution of urea is isotonic with 10% solution of sucrane .calculate molecular mass of urea​

Answer 1

Answer :

60 g mol−1

Solution :

πglucose=WB×R×TMB×V=(10g)×R×T(342 g mol−1)×R×T

πurea=WB×R×TMB×V=(1.754g)×R×TMB×R×T

since solutions area isotonic,πglucose=Purea

(10g)(342 g mol−1)=(1.754g)MBorMB=(1.754g)×(342g mol−1)(10g)

=59.98≈60 g mol−1.

Answer 2

The molecular mass of urea​ is 59.9868 grams.

Explanation:

• The Van't Hoff Factor gauges a solute's impact on different colligative properties of a solution. The amount of solute in the solution affects coagulative qualities that is the relative reduction of vapour pressure, osmotic pressure, boiling point elevation, and freezing point depression. The Van't Hoff factor is the ratio between the concentration of a substance as determined by its mass and the concentration of particles that are actually formed when it is dissolved and i stands for it.
• According to the given equation, it is given that, 1.78% solution of urea is isotonic with 10% solution of sucrane. This means that Van't Hoff factor that is i is 1 here.
• Now, according to the given information, the osmotic pressures of both sucrane and urea are same. That is, $\pi _{sucrane} =\pi _{urea}$.

Now, here $C_{1} RT = C_{2} RT$, where $C_{1}$ is the concentration of solute in sucrane and $C_{2}$ is the concentration of solute in urea. Also, R is the gas constant here T is the absolute temperature here.

Then, we get,

$\frac{10}{342} = \frac{1.754}{x}$, where the molecular weight of sucrane is 342.

Now, we get,

x = $\frac{1.754 * 342}{10}$.

Or, x = 59.9868 grams.

Thus, the molecular mass of urea​ is 59.9868 grams.

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