Question

The vapor pressure of an aquous solutions of sucrose at 373k is found to be 750mm Hg molarity of the solution at the same temperature will be

Answer 1

Answer:

Given that  

pressure at 373 of solution is 750 mm Hg.  

Pressure of solvent means water at 373 K is 760 mmHg

According to the Raoult’s law;

Psoln = PH2O XH2O  

750 = 760 (XH2O)  

mole fraction; XH2O = 0.987  

mole fraction = moles of water / total number of moles (water + solute )

Here mass of water is 1.00 kg or 1000 g

Therefore;  

Number of moles = amount in g / molar mass

= 1000g  18.02 g/ mole=  55.6 moles H2O,  

And from mole frcation;

0.987 = 55.6 /(55.6 + x)  

x = moles glucose = 0.777 moles  

and  molality = moles solute / kg solvent, molality = 0.777 m