pH Scale: Some acids are weaker than others. It is the same with alkalis. The strength of an acid or alkali is shown using the pH scale which goes from 0 to 14.
On this scale,
- An acidic solution has a pH number less than 7.
- An alkaline solution has a pH number greater than 7.
- A neutral solution has a pH number of exactly 7.
The smaller the number the stronger the acid. The larger the number the stronger the alkaline.
Universal Indicator: Supplied as a solution or as a paper and has a range of colours to specifically identify the pH of a solution.
Use of Universal Indicator to Measure pH of Aqueous Solution:
- If using universal indicator solution, a few drops of this solution is added to the aqueous solution and colour change is observed and matched to specific pH using the pH scale.
- If using universal indicator paper, this paper is dipped into the aqueous solution and colour change is observed and matched to specific pH using the pH scale.
Universal Indicator and pH Scale:
The colour change of the universal indicator is matched to a specific colour on the pH scale, which tells the approximate pH.