Lesson 3

Logarithms are used to measure things that can have extremely large or extremely small values, such as earthquake amplitude or magnitude, respectively. Along the same lines, logarithms are used to measure acidity of solutions. Have you ever tasted lemon juice or seawater? Lemon juice and seawater are known as solutions. Lemon juice is considered an acidic solution, and seawater is a basic or alkaline solution. Solution acidity is dependent on the concentration of hydrogen ions in the solution. The concentrations can be a very small number, so a pH scale is used to compare solutions’ acidity. The pH scale ranges from 0 to 14, as shown in the table.

From PRINCIPLES OF MATHEMATICS 12 by Canavan-McGrath et al. Copyright Nelson Education Ltd. Reprinted with permission.

Try This 3

A pH scale is used to measure the acidity of solutions, and pH can be found using p(x) = −log x, where x represents the concentration of hydrogen ions and is measured in moles per litre (mol/L).

Use the pH chart to help determine the hydrogen ion concentration of soapy water by filling in the following table.

Save your responses in your course folder.