Chapter 13, Problem 151AP

Interpretation Introduction

Interpretation:

The molecular formula and molar mass of the compound is to be determined with given mass percent of elements, mass of compound, mass of solvent, and freezing temperature.

Concept Introduction:

The property that depends on the concentration of solute molecules and not on the identity of solute is termed as colligative property. Freezing point depression is a colligative property.

The depression in freezing point by the addition of a solute in a pure substance is calculated as follows:

$\Delta T_f=K_f.m$

Here, $\Delta T_f$ is the depression in freezing point, $K_f$ is the freezing point constant, and $m$ is the molality.

The number of moles of a species is given by the following expression:

$\text{Number}\text{of}\text{moles}=\frac{\text{Given}\text{mass}}{\text{Molar}\text{mass}}$

The molality of a solution can be calculated as

$\text{Molality}\text{=}\frac{\text{moles}\text{of}\text{solute}}{\text{mass}\text{of}\text{solvent(kg)}}$