Chapter 12.3, Problem 3PE

Interpretation Introduction

Interpretation

The molality of solution that contains $7.78g$ urea in $203g$ of water should be calculated.

Concept introduction

Molality: Molality is defined as number of moles of the solute present in the kilogram of the solvent.

$\text{Molality =}\frac{\text{number of moles of the solute}}{\text{kg of solvent}}$

Moles: One mole is equivalent to the mass of the substance consists same number of units equal to the atoms present in $\text{12}\text{g}$ of ${}^{\text{12}}\text{C}$.

From given mass of substance moles could be calculated by using the following formula,

$\text{Moles}\text{of}\text{substance }\text{= }\frac{\text{Given}\text{mass}\text{of}\text{substance}}{\text{Molecular}\text{mass}}$

Mass: It is the quantitative measure of a substance. The amount of matter present in substance is expressed as mass. The $S.I.$ unit of mass is $kg$.