Indicators
Litmus, phenolphthalein and methyl orange are the common indicators which determine the acidic and basic nature of a substance by a characteristic change in their colour. This is note is detailed explanation of indicators used to distinguish acid and basic properties of compound.
Summary
Litmus, phenolphthalein and methyl orange are the common indicators which determine the acidic and basic nature of a substance by a characteristic change in their colour. This is note is detailed explanation of indicators used to distinguish acid and basic properties of compound.
Things to Remember
- Indicators are the chemical substances which are used for identifying whether a given substance is acid or base.
- Litmus, phenolphthalein and methyl orange are the common indicators which determine the acidic and basic nature of a substance by a characteristic change in their colour.
- The ordinary indicators do not give information about the strength of acidic or basic substances.
- Universal indicator is used for identifying the acidic and basic characters of substances and also indicates the strength of acidic and basic characteristic of substances.
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Indicators
Indicators are the chemical substances which are used for identifying whether a given substance is acid or base. Indicators cannot take part in chemical reaction and do not affect the chemical reaction but show the end of the chemical reaction.
Litmus, phenolphthalein and methyl orange are the common indicators which determine the acidic and basic nature of a substance by a characteristic change in their colour. The ordinary indicators do not give information about the strength of acidic or basic substances. They show the following change of colour in acidic, alkaline and neutral solutions:
| Common Indicators | Acidic solution | Alkaline solution | Salt solution |
| Red litmus | No change in colour | Changes into blue colour | No change in colour |
| Blue litmus | Changes into red colour | No change in colour | No change in colour |
| Methyl orange | Changes into red colour | Changes into yellow colour | Faint orange in colour |
| Phenolphthalein | No change in colour | Changes into pink colour | No change in colour |
| Red cabbage juice | Changes into red colour | Changes into green colour | Changes into faint purple colour |
Universal indicator is a mixture of simple indicators. It is used for identifying the acidic and basic characters of substances and also indicates the strength of acidic and basic characteristic of substances. It is prepared by the combination of common indicators found in green blue solution or yellow litmus paper. In universal indicator, red or intense red colour indicates acidic nature while light blue or intense blue colour indicates alkaline nature.
Differences between ordinary indicator and universal indicator
| Ordinary indicator | Universal indicator |
| It is a weak organic substance made from lichens. | It is a mixture of ordinary indicators. |
| It does not indicate the strength of acid and base. Example: Litmus paper. | It indicates the strength of acid and base. Example: PH paper |
Lesson
Acid Base And Salt
Subject
Science
Grade
Grade 10
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