# Question #f2c30

##### 1 Answer

The molar mass of the coumpound is **280 g/mol** and its molecular formula is

So, you know that when you dissolve **100 mg** of your unknown compound in **1 g** of benzene, you get a lower freezing point than that of pure benzene.

This means that you can use the *freezing-point depression* formula to solve for the solution's molality.

**cryoscopic constant**;

For molecular compounds the van't Hoff factor is equal to **1**.

Solve for the molality of the solution by

Since molality is defined as moles of solute per kilogram of solvent, you can calculate the number of moles of your unknown compound by

Determine the compound's molar mass by using its given mass

To determine its molecular formula, use its empirical formula

This will get you

Therefore, your compound's molecular formula is

**SIDE NOTE** *If you go by the number of sig figs you gave for the mass of unknown compound dissolved in benzene, the answer should be 300 g/mol.*

*However, I'm quite sure that the answer's supposed to be 280, so I'll leave it with two sig figs.*