Stinging hair of nettle leaves inject fluid in the human body causing burning pain. The fluid is
- A.Methanoic acid
- B.Tartaric acid
- C.Hydrochloric acid
- D.Sulphuric acid
Correct answer
Explanation
The correct answer is A, Methanoic acid. The stinging hairs of the nettle inject methanoic acid, also called formic acid, which causes the burning pain.
Nettle is a herbaceous plant whose leaves carry fine, brittle hairs. When the skin brushes against them, the tips break and the hairs inject methanoic acid (HCOOH) along with other irritants into the skin. The same acid is present in the sting of ants and bees. A traditional remedy is to rub the area with the leaf of the dock plant, which often grows beside nettle; a mild base such as baking soda solution also neutralises the acid and eases the pain.
B is wrong: tartaric acid is found in tamarind and grapes and is a component of baking powder.
C is wrong: hydrochloric acid is secreted in the human stomach to help digestion, not by plants.
D is wrong: sulphuric acid is a strong mineral acid used in industry and car batteries, not a natural plant fluid.
Exam tip: methanoic (formic) acid = ant sting and nettle; lactic acid = curd and tired muscles; citric acid = lemon; tartaric acid = tamarind.
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