Question

A 200-mg sample of a purifed compound of unknown molar mass is dissolved in benzene and diluted with that solvent to a volume of 25.0 cm3 . The resulting solution is found to have an osmotic pressure of 0.0105 atm at 300 K. What is the molar mass of the unknown compound?

Answer 1

Answer: The molar mass of the unknown compound is 18765.7 g/mol

Step-by-step explanation:

`\pi =CRT`

`\pi` = osmotic pressure = 0.0105 atm

C= concentration in Molarity

R= solution constant = 0.0821 Latm/Kmol

T= temperature = 300 K

For the given solution: 200 mg or 0.2 grams of unknown compound is dissolved in 25 ml of solution.

`Molarity=\frac{\text{Mass of solute}* 1000}{\text{Molar mass of solute}* \text{volume of solution in ml}}`

Putting in the values we get:

`C=(0.2* 1000)/(M* 25)`

`0.0105 =(0.2* 1000)/(M* 25)* 0.0821* 300`

`M=18765.7g/mol`

The molar mass of the unknown compound is 18765.7 g/mol