The carbohydrate digitoxose contains 48.64% carbon and 8.16% hydrogen. The addition of 18.0 g of this compound

Question:

The carbohydrate digitoxose contains 48.64% carbon and 8.16% hydrogen. The addition of 18.0 g of this compound to 100. g of water gives a solution that has a freezing point of -2.2°C.
a. What is the molecular formula of the compound?
b. What is the molar mass of this compound to the nearest tenth of a gram?