what is universal indicator? Give 2 examples of natural indicator
Answers
Explanation:
Indicators are chemical compounds that tell us whether a substance is acidic or basic by changing its colour. When added to an acidic solution or a basic solution, indicators change their colour and this change in colour is different for the acids and bases. The indicator thus help us to decide whether a given solution is acidic or basic in nature.
The indicators that are obtained from plants are known as natural indicators.
Examples – Turmeric, china rosa, red cabbage and grape juice.
Some flowers such as the hydrangeas can also determine whether a substance is acidic or basic. Hydrangeas turn blue if the soil is acidic, purple if the soil is neutral and pink if the soil is basic. The colour intensity depends on the amount of acid and base present in the soil.
Universal indicators are a mixture of organic dyes that give different colours at different concentrations of hydrogen ions in solution.
Example – pH paper or solution
Answer:
thymol blue, methyl red, bromothymol blue, methyl orange are some common universal indicators
Explanation:
pH range Description Colour
< 3 Strong acid Red
3–6 Weak acid Orange or Yellow
7 Neutral Green
8–11 Weak alkali Blue
> 11 Strong alkali Indigo or Violet
now different indicators give different colours
Universal indicator components
Indicator Low pH colour Transition pH range High pH colour
Thymol blue Red 1.2 – 2.8 Yellow
Methyl orange Red 3.2 – 4.4 Yellow
Methyl red Red 4.8 – 6.0 Yellow
Bromothymol Yellow 6.0 – 7.6 Blue
blue
Thymol blue Yellow 8.0 – 9.6 Blue
Phenolphthalein Colourless 8.3 – 10.0 Fuchsia