Question

At 25°c, 3g of solute in 100ml of aqueous solution gave an osmotic pressure of 2.5. Calculate molar mass of solute

Answer 1

Answer-

The molar mass of the solute is 293.6 g/mol

Explanation:

To calculate the concentration of solute, we use the equation for osmotic pressure, which is:

\pi=iMRTπ=iMRT

Or,

\pi=i\times \frac{\text{Mass of solute}\times 1000}{\text{Molar mass of solute}\times \text{Volume of solution (in mL)}}\times RTπ=i×

Molar mass of solute×Volume of solution (in mL)

Mass of solute×1000

×RT

where,

\piπ = osmotic pressure of the solution = 2.5 atm

i = Van't hoff factor = 1 (for non-electrolytes)

Mass of solute = 3 g

Volume of solution = 100 mL

R = Gas constant = 0.0821\text{ L. atm }mol^{-1}K^{-1}0.0821 L. atm mol

−1

K

−1

T = temperature of the solution = 25^oC=[273+25]=298K25

o

C=[273+25]=298K

Putting values in above equation, we get:

\begin{gathered}2.5atm=1\times \frac{3\times 1000}{\text{Molar mass of solute}\times 100}\times 0.0821\text{ L. atm }mol^{-1}K^{-1}\times 298K\\\\\text{Molar mass of solute}=\frac{1\times 3\times 1000\times 0.0821\times 298}{2.5\times 100}=293.6g/mol\end{gathered}

2.5atm=1×

Molar mass of solute×100

3×1000

×0.0821 L. atm mol

−1

K

−1

×298K

Molar mass of solute=

2.5×100

1×3×1000×0.0821×298

=293.6g/mol

Explanation:

hope it helped you