Which of the following gases is obtained by the reaction of water with calcium carbide?
Answer: C
Calcium carbide reacts with water to give acetylene:
\[ \mathrm{CaC_2 + 2H_2O \rightarrow C_2H_2 + Ca(OH)_2} \]
The reaction was once used in carbide lamps, and acetylene burning in oxygen gives the 3,300°C flame used for welding and cutting steel.
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Sodium metal is kept under
Answer: D
Sodium is stored under kerosene. It reacts violently with water and even with the moisture in air, so it must be kept away from both.
Kerosene works because it is a hydrocarbon that does not react with sodium and is dense enough to keep the metal covered. Sodium in air quickly forms an oxide crust and can catch fire.
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The disease not transmitted by house-fly is
Answer: C
Dengue fever is not spread by the housefly. It is transmitted by the bite of the Aedes aegypti mosquito.
The housefly carries disease mechanically, on its feet and mouthparts, from filth to food - which is how it spreads cholera, dysentery, typhoid and diarrhoea.
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Insulin was discovered by:
Answer: A
Frederick Banting, with Charles Best, discovered insulin at the University of Toronto in 1921.
They extracted it from dog pancreas and showed it controlled blood sugar in diabetic dogs, then in patients. Banting shared the 1923 Nobel Prize and sold the patent for a dollar.
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Which amongst the following is the acronym of PVC?
Answer: A
PVC stands for polyvinyl chloride, made by polymerising vinyl chloride, CH2=CHCl.
Rigid PVC is used for pipes and window frames; adding a plasticiser makes it flexible for cable insulation and sheeting. It is the third most produced plastic in the world.
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In an atomic explosion, enormous energy is released which is due to
Answer: C
The energy of an atomic explosion comes from the conversion of mass into energy.
The fragments of a fissioned uranium nucleus weigh slightly less than the original, and the missing mass appears as energy according to Einstein's relation:
\[ E = mc^2 \]
Because \( c^2 \) is so large, a gram of mass yields about 9 × 1013 joules.
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Noise, or noise pollution, is measured in
Answer: C
The decibel measures the loudness or intensity of sound.
It is logarithmic: 10 dB is a tenfold increase in intensity, so the scale can cover the enormous range the ear handles. Frequency, which determines pitch, is measured in hertz instead - cycles per second.
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Which amongst the following is not true about the chandrayan1?
Answer: B
The false statement is the rocket's serial number: Chandrayaan-1 was launched by PSLV-XL C11, not C13.
The other statements are correct. It was launched by ISRO in October 2008, entered lunar orbit on 8 November 2008, and the project had been announced by Prime Minister Vajpayee on 15 August 2003.
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Where does the cabbage store food?
Answer: D
The cabbage stores its food in the leaves. The head is a tight rosette of thickened, overlapping leaves packed with reserves.
Cauliflower stores food in the flower head, potato in the stem tuber and carrot in the root.
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Brass gets discoloured in air because of the presence of which of the following gases in air?
Answer: B
Brass discolours in air because of hydrogen sulphide, which reacts with the copper in the alloy to form a dark film of copper sulphide.
The gas is present in traces in polluted air and near decaying organic matter. Silver tarnishes black for exactly the same reason.
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