Question

8. (6 pts) Determine the vapor pressure at 25 C of an aqueous ethylene glycol (CIO) solution at is 14.8% C,H602 by mass. The vapor pressure of pure water at 25 °C is 23.8 torr A) 3.52 tor B) 22.7 torr C) 1.14 torr D) 20.3 torr Show work:

Answer 1

14.8% C_2H_6O_2 means 14.8 gm C_2H_6O_2 remain in 100 gm solution. So, mass of solvent = (100 - 14.8) = 85.2 gm molar mass of C_2H_6O_2 = (2 times 12 + 6 times 1 + 2 times 16) = 62 gm/mole. Therefore 14.8 gm C_2H_6O_2 = 14.8/62 = 0.2387 mole. 85.2 gm water = 85.2/18 = 4.73 mole. Therefore Mole fraction of C_2H_6O_2 = 0.2387/(4.73 + 0.2387) = 0.048 we know, p_1^0 - p_1/p_1^0 = x_2 23.8 - p_1/23.8 = 0.048 therefore p_1 = 22.66 torr p_1 = 22.7 torr. So, option (B) 22.7 tor