Which one of the following acids is secreted by leaves of Nettle that causes painful stings ?
- A.Methanoic acid
- B.Citric acid
- C.Tartaric acid
- D.Acetic acid
Correct answer
Explanation
The correct answer is A, Methanoic acid. The stinging hairs on nettle leaves inject methanoic acid, also called formic acid, into the skin, which causes the burning pain.
The nettle is a herbaceous plant whose leaves and stems carry fine hollow hairs. When touched, the brittle tips break and the hairs act like tiny needles, pushing methanoic acid (HCOOH) into the skin. The same acid is injected by ant bites and bee stings. The traditional remedy is to rub the spot with the leaf of the dock plant, which often grows beside nettle, while a mild base such as baking soda solution neutralises the acid.
Option B is wrong because citric acid is found in lemons and oranges. Option C is wrong because tartaric acid is found in tamarind and grapes. Option D is wrong because acetic acid is the acid of vinegar.
Exam tip: nettle, ant sting and bee sting carry methanoic (formic) acid; vinegar has acetic acid, curd lactic acid and tomato oxalic acid.
Practice Questions
View allBronze is an alloy of copper and
- A.nickel
- B.iron
- C.tin
- D.aluminium
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Bronze is an alloy of copper and tin, usually about 88 parts copper to 12 parts tin. Adding tin makes copper harder, stronger and easier to cast, and bronze also resists corrosion well.
Read the full explanation →Which one of the following instruments is used for measuring moisture content of air?
- A.Hydrometer
- B.Hygrometer
- C.Hypsometer
- D.Pycnometer
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A hygrometer measures humidity, that is, the amount of water vapour or moisture in the air. The name comes from the Greek "hygros", meaning wet.
Read the full explanation →Which one of the following elements is present in the green pigment of leaves?
- A.Magnesium
- B.Iron
- C.Calcium
- D.Copper
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The green pigment of leaves is chlorophyll, and a magnesium atom sits at the centre of every chlorophyll molecule.
Read the full explanation →Consider the following actions :
1. Detection of car crash/collision which results in the deployment of airbags almost instantaneously
2. Detection of accidental free fall of a laptop towards the ground which results in the immediate turning off of the hard drive
3. Detection of the tilt of the smartphone which results in the rotation of display between portrait and landscape mode
In how many of the above actions is the function of accelerometer required?
- A.Only one
- B.Only two
- C.All three
- D.None
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An accelerometer measures acceleration, including the pull of gravity, and each of the three actions depends on reading it. An accelerometer is a small sensor, today usually a MEMS (micro-electro-mechanical system) chip, that senses changes in speed and the direction of gravity.
Read the full explanation →Consider the following statements :
1. Carbon fibres are used in the manufacture of components used in automobiles and aircrafts.
2. Carbon fibres once used cannot be recycled.
Which of the statements given above is/are correct?
- A.1 only
- B.2 only
- C.Both 1 and 2
- D.Neither 1 nor 2
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Carbon fibre is widely used in cars and aircraft for its strength and low weight, and it can be recovered and recycled.
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