Question

Calculate the vapor pressure at 50°C of a coolant solution that is 57.0:43.0 ethylene glycol-to-water by volume. At 50.0°C, the density of water is 0.9880 g/mL, and its vapor pressure is 92 torr. The vapor pressure of ethylene glycol is less than 1 torr at 50.0°C. Answer in torr

Answer 1

given: density of water= 0.9880 g/ml at 50^oC, ethylene glycol: water ratio= 57:43, vapour pressue of water = 92 torr

Density = mass/volume

therefore, mass of water = 43 x 0.98 = 42.48g

mass of ethylene glycol = 57 x 1.11 (density of ethylene glycol) = 63.27g

moles of ethylene glycol = (63.27 x1 )/ 62.07 = 1.019 moles

moles of H₂O = (42.48 x 1) / 18 = 2.36 moles

total moles = 1.019 +2.36 = 3.379

mole fraaction of water = 2.36/3.379 = 0.6984

vapor pressure of solution = 0.6984 x 92 torr = 63.48 torr