Question

Vapor obtained by evaporating 0.495 grams of an unknown liquid is collected in a 127 mL flask. At 371 K, the pressure of the vapor in the flask is 754 torr. What is the molar mass in g/mol?

Answer 1

Answer:

The molar mass in g/mol is 121.4 g/m

Explanation:

Let's apply the Ideal Gases Law to solve this:

P . V = n . R. T

V = 125 mL → 0.125L

P = 754 Torr

760 Torr ___ 1 atm

754 Torr ____ (754 / 760) = 0.992 atm

Moles = Mass / Molar mass

0.992 atm . 0.125L = (0.495 g / MM) . 0.082 . 371K

(0.992 atm . 0.125L) / (0.082 . 371K) = (0.495 g / MM)

4.07x10⁻³ mol = 0.495 g / MM

MM = 0.495 g / 4.07x10⁻³ mol → 121.4 g/m