E-PolyLearning

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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Answer: (c).Helium

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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Answer: (d).oxygen and acetylene

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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Answer: (b).deliquescence

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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Answer: (c).cutting very hard substances

20. The average salinity of sea water is
a. 3%
b. 3.5%
c. 2.5%
d. 2%
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Answer: (b).3.5%

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