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Q66
(NDA-I/2024)
Science & Technology › Basic Science (Physics, Chemistry, Biology)
Official Key
Litmus, a well-known acid-base indicator, is derived from :
Explanation
Litmus is a widely used natural acid-base indicator that is extracted from lichens. Lichens are unique composite organisms consisting of a symbiotic association between a fungus and an alga (or cyanobacterium).
- Source: The dye is primarily obtained from various species of lichens, such as Roccella tinctoria and Lecanora tartarea.
- Function: It is used to determine the acidity or alkalinity of a substance. In its neutral state (distilled water), litmus has a mauve (purple) color.
- Chemical Reaction: When exposed to an acidic solution, litmus turns red. Conversely, when exposed to a basic (alkaline) solution, it turns blue.
As per NCERT Science standards, litmus is the most commonly used natural indicator, typically available either as a solution or in the form of paper strips (litmus paper).
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