Question

The vapor pressure of pure water at 37C is 47.1 torr. What would be the vapor pressure of an aqeous solution at 37C containing 40g of Glucose (C6H12O6) dissolved in 200g of water?

Answer 1

Po = 47.1 torr

mass of glucose = 40 g
Molar mass of glucose = 180 g/mol
number of moles of glucose, n1 = mass / molar mass
                                                                  = 40/180
                                                                  = 0.222 mol

mass of water = 200 g
Molar mass of water = 18 g/mol
number of moles of water, n2 = mass / molar mass
                                                                  = 200/18
                                                                  = 11.111 mol

mole fraction, x = n2 / (n1+n2)
                                 = (11.111) / (0.222 + 11.111)
                                 = (11.111) / (0.222 + 11.111)
                                 = 0.98

use:
P = Po*x
    = 47.1 * 0.98
    =46.2 torr
Answer: 46.2 torr