Tiêu đề DPP 9 Solutions.pdf ✅

Class : XIIth Subject : CHEMISTRY Date : DPP No. : 9 1 (b) Bronze is mixture of Cu and Sn 2 (c) In the extraction of Al,Al2O3 is melted with cryolite[Na3(AlF6)]. Cryolite improves the electrical conductivity of the alumina and lowers the m.p. of the mixture to about 950°C 3 (a) In bauxite ore, only Al2O3 reacts with conc NaNO and fo sodium meta aluminate. This, further dissolves in water Al2O3 + 2H2O + 2NaOH 500 K 35 bar2NaAlO2 + 3H2O NaAlO2 + 2H2O→2NaAl(OH))4 4 (c) A mineral containing phosphates oscerium, thorium and other rare earths, with some occluded helium. 5 (d) Luster of metals is due to the presence of mobile electrons 6 (a) Rochelle salt is potassium, sodium tartarate. 7 (d) Amphoteric compounds are soluble in both alkali and acid. 8 (d) ∆ Gffor sulphides > ∆Gfof CS2 and H2S and thus, C and H2 cannot reduce metal sulphide. 9 (a) It is a fact. 10 (c) Among cuprite [Cu2O], chalcocite [Cu2S], chalcopyrite [CuFeS2] and malachite [Cu(OH)2 .CuCO3]; only chalcopyrite is an ore which contains both Fe and Cu 11 (b) Galena is an ore of Pb containing SnO2. 12 (a) It is a fact. 13 (a) FeO can form slag with SiO2, Topic :- Isolation Elements Solutions
SiO2 +FeO→FeSiO3. 14 (c) This is Van-Arkel method for purification of Ti. 15 (a) Diaspore is an ore of aluminium containing Al2O3 ∙ H2O . 16 (c) Quartz is found in many varieties which have different colour due to impurities, eg, amelthyst (purple), opel (white) carnelian and agate ∴ Agate is SiO2 17 (a) In the metallurgy of zinc, reduction of roasted ore (ZnO) gives impure zinc (in fire-clay retort) called spelter. 18 (d) Rock salt is NaCl. 20 (a) Ore pitch blende is main source of radium
ANSWER-KEY Q. 1 2 3 4 5 6 7 8 9 10 A. B C A C D A D D A C Q. 11 12 13 14 15 16 17 18 19 20 A. B A A C A C A D D A