A mixture is prepared that is 5.0% (w/w) of an unknown substance mixed with naphthalene (molar mass = 128.2 g mol^-1). The freezing
point of this mixture is found to be 77.3 °C. What is the molar mass of the unknown substance? (The melting point of naphthalene is 80.2 °C and Kf = 6.9 °C m^-1.)
The molar mass of the unknown substance =

A 0.2436 g sample of an unknown substance was dissolved in 20.0 mL of cyclohexane. The density of cyclohexane is 0.779 g/mL. The freezing-point depression was 2.5 degrees Celsius. Calculate the molar mass of the unknown substance

1. How many grams of ethylene glycol, C2H4(OH)2, are needed per kilogram of water to protect radiator fluid against freezing down to -10°C?

2. For benzene, C6H6, the freezing point constant, Kf, is 5.12 K oC/m and its normal freezing point is 5.5°C. What is the freezing point of a solution containing 100.0 g of benzene and 20.0 g of naphthalene (C10H8)?

3. When 5.0 g of an unknown substance is dissolved in 100.0 g of water, the freezing point of the solution decreases by 1.5°C. What is the molar mass of the unknown substance if the compound does not dissociate to form ions in solution?

4. If 2.00 moles of a substance is dissolved in 1.00 kg of water, the freezing point of the solution decreases by 7.44°C. Does this substance dissociate to form ions in solution? Explain why.

5. Calculate the freezing point of a 0.2 m CaCl2 aqueous solution, assuming it dissociates completely to form ions in solution.