Question

The common laboratory solvent water is often used to purify substances dissolved in it. The vapor pressure of water is 23.76 mm Hg at 25 °C.

In a laboratory experiment, students synthesized a new compound and found that when 45.89 grams of the compound were dissolved in 160.6 grams ofwater, the vapor pressure of the solution was 23.10 mm Hg. The compound was also found to be nonvolatile and a non-electrolyte.

What is the molecular weight of this compound?

Answer 1

The molecular weigh of the compound can be determined by using the formula,

(P1 - P) / P1 = (w2 × M1) / ( M2× w1)

Where p1 is the vapour pressure of pure solvent and p is vapour pressure of solution.

w1 and w2 are the masses and M1 and M2 are the molar masses of solvent and solute respectively.

Putting all the values in formula above,

(23.76 - 23.10) / 23.76 = (45.89 × 18.016) / (M2 × 160.6)

M2 = 185.32

So the molecular weight of the compound is 185.32 g/mol

answered by: anonymous