Definitions [8]
Define acids according to Bronsted-Lowry theory.
A substance that donates a proton \[\ce{(H+)}\] to another substance is known as an acid.
Define conjugate acid-base pair.
A pair of an acid and a base differing by a proton is called conjugate acid-base pair.
The materials which indicate the presence of an acid or a base in a solution. These are called Acid-Base Indicators or sometimes simple indicators.
pH scale is a scale for measuring the hydrogen ion concentration in a solution.
Define pOH.
The pOH of a solution can be defined as the negative logarithm to the base 10, of the molar concentration of OH− ions in solution.
pOH = -log10[OH-]
Define pH.
The pH of a solution is defined as the negative logarithm to the base 10, of the concentration of H+ ions in solution in mol dm–3.
pH is expressed mathematically as
pH = -log10 [H+] or pH = -log10 [H3O+]
Define buffer solution.
A buffer solution is defined as a solution which resists drastic changes in pH when a small amount of strong acid, strong base, or water is added to it.
Define Acidic buffer solution.
A solution containing a weak acid and its salts with strong base is called an acidic buffer solution.
Key Points
- The pH scale (0–14) measures the concentration of H⁺ ions in a solution; values < 7 indicate acids, > 7 indicate bases, and 7 is neutral.
- A universal indicator shows different colours at different pH levels, helping to determine the strength of an acid or base.
- Strong acids/bases produce more H⁺ or OH⁻ ions in solution, while weak acids/bases produce fewer ions at the same concentration.
