Lime water turns milky when which gas is passed through it?
- A.Hydrogen
- B.Oxygen
- C.Carbon dioxide
- D.Nitrogen
Correct answer
Explanation
The correct answer is C, carbon dioxide. Carbon dioxide reacts with lime water, a solution of calcium hydroxide, to form insoluble calcium carbonate, whose fine white particles make the liquid look milky; if more of the gas is passed the milkiness disappears as soluble calcium bicarbonate is formed, and that second step is often the harder half of the question. Option A, hydrogen, is wrong because it is neutral to lime water and is tested by the pop it makes when burnt. Option B, oxygen, is wrong because it is tested by the glowing splint that bursts into flame. Option D, nitrogen, is wrong because it is unreactive at room temperature and gives no such test. The same reaction explains why lime is used in whitewashing, where the carbon dioxide of the air hardens the coat.
Read the full article: Important Gases and Their Uses: Notes and PYQs
Practice Questions
View allWhich gas is typically produced when a metal reacts with an acid?
- A.Carbon dioxide
- B.Oxygen
- C.Hydrogen
- D.Nitrogen
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A metal more reactive than hydrogen displaces it from a dilute acid, so zinc with dilute sulphuric acid gives zinc sulphate and hydrogen gas, and this is the standard laboratory preparation of the gas; the test is that it burns with a pop.
Read the full explanation →Which of the following is a radioisotope of hydrogen?
- A.Xenon
- B.Technetium
- C.Thorium
- D.Tritium
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Hydrogen has three isotopes: protium with one proton and no neutron, deuterium with one neutron, which gives heavy water, and tritium with two neutrons, which is radioactive and is used in fusion research and in luminous dials.
Read the full explanation →Ozone depletion is greatest near
- A.tropics
- B.equator
- C.poles
- D.oceans
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Chlorine released from chlorofluorocarbons destroys ozone fastest where polar stratospheric clouds form in the extreme cold of winter, because those ice clouds hold the chlorine compounds that sunlight then breaks up; the thinning is therefore deepest over Antarctica, where it is called the ozone hole, and is seen over the…
Read the full explanation →Which gas is commonly known as laughing gas?
- A.Nitric oxide
- B.Nitrogen dioxide
- C.Nitrous oxide
- D.Ammonia
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It is called laughing gas because it produces a feeling of elation when inhaled in small quantities, and it is used as a mild anaesthetic in dentistry and minor surgery and as the propellant in whipped cream; it is also a greenhouse gas.
Read the full explanation →Which gas is filled in electric bulbs so that the filament lasts longer?
- A.Oxygen
- B.Argon
- C.Chlorine
- D.Carbon dioxide
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Argon is chemically inert, so the hot tungsten filament does not react with it, and its presence also slows the evaporation of tungsten, which is why bulbs are filled with argon, sometimes mixed with nitrogen, instead of being left as a vacuum.
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