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⁞ Chemistry

General Science ➤ Chemistry ➤ 2
Question 11
Q11.  Which one of the following metals is used to galvanise iron?
 

Answer :  Zinc


Galvanization is the process of applying a protective zinc coating to steel or iron, in order to prevent rusting. The term is derived from the name of Italian scientist Luigi Galvani. Although galvanization can be done with electrochemical and electro-deposition processes, the most common method in current use is hot-dip galvanization, in which steel parts are submerged in a bath of molten zinc.
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Question 12
Q12.  Which of the following gases is mixed with oxygen for breathing by divers in aqualungs?
 

Answer :  Nitrogen


For deep see diving, gas mixtures other than normal atmospheric air (21% oxygen, 78% nitrogen, 1% trace gases) can be used, so long as the diver is properly trained in their use. The most commonly used mixture is Nitrox, also referred to as Enriched Air Nitrox (EAN), which is air with extra oxygen, often with 32% or 36% oxygen, and thus less nitrogen, reducing the likelihood of decompression sickness or allowing longer exposure to the same pressure with equal risk.
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Question 13
Q13.  Iodine can be separated from a mixture of Iodine and Potassium Chloride by:
 

Answer :  sublimation


Iodine is well known to sublime (change from solid to gas without under going the liquid phase when heated. However potassium chloride has a melting point much higher than that of iodine. Therefore, a mixture of iodine and potassium chloride can be separated by using a sublimation apparatus, with solid iodine collected on condensation of its vapour on a cold surface.
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Question 14
Q14.  Electric fuse is an alloy of:
 

Answer :  tin and lead


Electric fuse is an alloy of tin and lead in ratio of 1:1.
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Question 15
Q15.  When Arsenic atoms are added to Germanium lattice, it becomes a/an:
 

Answer :  Extrinsic semiconductor


When a pentavalent (donor) impurity, like arsenic, is added to germanium, it will form covalent bonds with the germanium atoms, leaving 1 electron relatively free in the crystal structure. Pure germanium may be converted into an n-type semiconductor by “doping” it with any donor impurity having 5 valence electrons in its outer shell. Semiconductors which are doped in this manner – either with N- or P-type impurities – are referred to as extrinsic semiconductors.
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