pH - Introduction
- The acidity of an aqueous solution depends on the number of H+ ions in solution
- The pH is defined as:
pH = -log[H+]
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- where [H+] is the concentration of hydrogen ions in mol dm–3
- Similarly, the concentration of H+ of a solution can be calculated if the pH is known by rearranging the above equation to:
[H+] = 10-pH
- The pH scale is a logarithmic scale with base 10
- This means that each value is 10 times the value below it. For example, pH 5 is 10 times more acidic than pH 6.
- pH values are usually given to 2 decimal places
- The relationship between concentration is easily seen on the following table
pH & [H+] Table