As hydroxide ions are removed,more water moleules ionise to keep constant. Hence the concentration of hydrogen ions increases and the pH becomes smaller than 7. The solution acidic.
Salts of weak acids and weak bases form neutral (or almost neutral) solution in water, e.g. ammonium ethanoate.
Ammonium ethanoate ionizes in water:
Ions react with hydrogen ions from the water to form ions react with hydrogen iones from the water to form Thus both hydrogen ione and hydroxide ions are removed from the water. As they are both equally removed, the pH remains the same,i.e.7.The solution is neutral.
4.9 Indicators
Most solutions of acids and alkalis are colourless. Therefore, We cannot identify them just by appearance. To test for acids and alkalis, we use indicators.
An indicator is substance tgat has different colours in acidic alkaline solutions.
One common indicator is litmus, a compound found in lichens growing on tress and rocks. Litmus is red in acid and blue in alkali. Other indicators are phenolphthalein and methyl orange