An aqueous solution containing 16.5 g of an unknown molecular (nonelectrolyte) compound in 106.0 g of water was found to have a freezing point of -1.9 ∘c. calculate the molar mass of the unknown compound.

The molar mass of the unknown compound is 152 g/mol.

Explanation:

Depression in freezing point is given by:

= Depression in freezing point

i= vant hoff factor = 1 (for non electrolyte)

= freezing point constant =

m= molality

Weight of solvent (water)= 106.0 g = 0.106 kg

Molar mass of unknown non electrolyte = M g/mol

Mass of unknown non electrolyte added = 16.5 g

Thus the molar mass of the unknown compound is 152 g/mol.

vanderwaal's forces of attraction are the electrostatic intermolecular forces that exist in a molecule due to the temporary or permanent dipoles that are developed in a molecule. in , the major intermolecular forces are dipole-dipole interactions as the molecule is polar (bent structure). so the vanderwaal's forces of interaction in between molecules are the permanent dipole-dipole interactions that develop due to the dipole that exists in between the polar h - s bond. the positively charged hydrogen atom is attracted towards the negative end of the dipole that is sulfur of the adjacent molecule. therefore, these forces of attraction are relatively stronger than that of london dispersion forces that exist in non polar molecules.