About science

16.	The inert gas which is substituted for nitrogen in the air used by deep sea divers for breathing, is
	A. Argon B. Xenon C. Helium D. Krypton

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17.	The gases used in different types of welding would include
	A. oxygen and hydrogen B. oxygen, hydrogen, acetylene and nitrogen C. oxygen, acetylene and argon D. oxygen and acetylene

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18.	The property of a substance to absorb moisture from the air on exposure is called
	A. osmosis B. deliquescence C. efflorescence D. desiccation

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19.	In which of the following activities silicon carbide is used?
	A. Making cement and glass B. Disinfecting water of ponds C. cutting very hard substances D. Making casts for statues

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20.	The average salinity of sea water is
	A. 3% B. 3.5% C. 2.5% D. 2%
21.	When an iron nail gets rusted, iron oxide is formed
	A. without any change in the weight of the nail B. with decrease in the weight of the nail C. with increase in the weight of the nail D. without any change in colour or weight of the nail

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22.	Galvanised iron sheets have a coating of
	A. lead B. chromium C. zinc D. tin

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23.	Among the various allotropes of carbon,
	A. coke is the hardest, graphite is the softest B. diamond is the hardest, coke is the softest C. diamond is the hardest, graphite is the softest D. diamond is the hardest, lamp black is the softest

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24.	The group of metals Fe, Co, Ni may best called as
	A. transition metals B. main group metals C. alkali metals D. rare metals

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25.	Heavy water is
	A. deuterium oxide B. PH7 C. rain water D. tritium oxide
26.	The chemical (ethyl mercaptan) added to the otherwise odourless LPG cooking gas for imparting a detectable smell to the gas is a compound of
	A. bromine B. fluorine C. chlorine D. sulphur

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27.	The element common to all acids is
	A. hydrogen B. carbon C. sulphur D. oxygen

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28.	Non stick cooking utensils are coated with
	A. Teflon B. PVC C. black paint D. polystyrene

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29.	Monazite is an ore of
	A. titanium B. zirconium C. iron D. thorium

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30.	Carbon, diamond and graphite are together called
	A. allotropes B. isomers C. isomorphs D. isotopes