PHYSICAL CHEMISTRY IN BRIEF

CHAP. 1: BASIC TERMS [CONTENTS] 41

U Main unit: mol kg−^1. This quantity is used mainly in connection with aqueous solutions of
electrolytes.

Example

A total of 58.5 g of NaCl has been mixed with 500 g of water. Calculate the molality of sodium

chloride given that you know its molar mass to beM = 58.5 g mol−^1.

Solution

By substituting into (1.14) we obtain

mNaCl=

58. 5 / 58. 5

0. 500

= 2mol kg−^1.

The molality of the obtained solution is 2 mol kg−^1.