Question

derive an equation for determination of molecular weight from osmotic pressure​

Answer 1

Answer: It is explained as follows:

Explanation:

The osmotic pressure  is the least amount of pressure that must be applied to a solution in order to prevent the passage of the pure solvent through a semipermeable membrane.

It depends on the concentration on the solute as:

 $\pi = C RT$  .....$(1)$

where $\pi$ is osmotic pressure, C is the concentration of solute, R is the  gas constant and T is the temperature.

Also $C = \frac{n}{V}$     ......$(2)$ (n is no. of moles, V is volume of solution)

$\pi = \frac{nRT}{V}$     .....$(3)$

As $n = \frac{w_{B} }{M_{B} }$    .....$(4)$

where $w_{B}$ is the amount of solute and $M_{B}$ is the molecular weight of the solute.

Now putting the value of equation $(4)$ in $(3)$ and rearranging;

$M_{B} =\frac{w_{B}RT }{V \pi }$

So this is equation which is used for determination of molecular weight from osmotic pressure.

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