Answer to Question #164472 in General Chemistry for Phyroe

Question

Calculate approximately how much methanol, CH3OH, would be needed for an automobile radiator holding 4 gal to keep the radiator solution from freezing until a temperature of negative 10.0 fahrenheit is reached.

Answer 1

Your strategy here will be to use the equation for freezing-point depression to determine the molality of the target solution, then use methanol's molar mass to find the mass of the compound needed to make this solution.

The equation that describes freezing-point depression looks like this

ΔTf = i⋅Kf⋅b, where

ΔTf - the freezing-point depression;

i - the van't Hoff factor;

Kf - the cryoscopic constant of the solvent;

b - the molality of the solution.