The acidity of a solution is dependent on the concentration
of hydrogen ions. The pH scale measures this acidity.
Syllabus reference
Reactivity 3.1.4  The pH scale can be used to describe the [H^{+}] of a solution:
 pH = –log_{10}[H^{+}]; [H^{+}] = 10^{–pH}
 Perform calculations involving the logarithmic relationship between pH and [H^{+}].
Guidance
 Include the estimation of pH using universal indicator, and the precise measurement of pH using a pH meter/probe.
 The equations for pH are given in the data booklet.
Tools and links
 Tool 1, Tool 2, Tool 3  What is the shape of a sketch graph of pH against [H^{+}]?
 Nature of science, Tool 2  When are digital sensors (e.g. pH probes) more suitable than analogue methods (e.g. pH paper/solution)?
