pH

• “pH” is a logarithmic scale used to specify the acidity or basicity of an aqueous solution.
• It is measured in a scale of 0 to 14.
• A pH of 7 is considered neutral, representing a balance of both hydronium and hydroxide ions in solution.
• Solutions with a pH value less than 7 are considered acidic; there is a greater concentration of hydronium ions (H3O+) in solution.
• Solutions with a pH value greater than 7 are considered basic or alkaline, as they have a greater concentration of hydroxide ions (OH-) in solution.
• The pH scale is a measure of the concentration of hydronium ions (H3O+) in a solution and it is defined by the negative logarithm (base 10) of the concentration of H3O+.
• Hence, pH = -log[H3O+]. Conversely, the concentration of hydronium ions in a solution can be calculated using the formula: [H3O+] = 10^(-pH).
• Factors such as temperature and dilution can influence the pH of a solution.
• A strong acid will fully dissociate in a solution to release hydronium ions, hence giving a low pH value.
• Whereas a weak acid will only partially dissociate, meaning it will have a higher pH value than a strong acid assuming both are at the same concentration.
• Strong bases such as sodium hydroxide (NaOH) and potassium hydroxide (KOH) dissociate fully to release hydroxide ions, resulting a high pH.
• Weak bases, on the other hand, are only partially ionised in solution, indicating a pH value closer to 7.
• pH values can be measured using conventional glass pH electrodes or by using indicators which display colour changes with respect to pH value range.
• It should be noted that the pH scale is logarithmic, indicating that a difference of 1 pH unit represents a ten-fold difference in hydronium ion concentration. For example, a solution with pH 2 is ten times more acidic than a solution with pH 3.