Tiêu đề DPP 3 Solutions.pdf ✅

Class : XIIth Subject : CHEMISTRY Date : DPP No. : 3 1 (d) Sulphide ores on roasting forms oxide and give SO2. 2 (a) The compounds which combine with impurities preseore (at high temperature) and remove them as a fls substance (slag) are known as flux. When basic impurities are present, an acidic flux is used and vice ― versa FeO + SiO2 → FeSiO3 Basic impurity acidic flux slag 4 (d) It is a fact. 5 (b) Wolframite ore [FeWO4] is present in tin stone as impurities and it has same mass per unit volume as that of tin stone. So, it is separated by electromagnetic separator because wolframite is magnetic in nature, hence it gets attached by magnet while tin stone does not 6 (b) Fe ores are magnetic in nature. 7 (b) Because reduction of highly electropositive elements, (e.g., alkali metals, alkaline earth metals and Al) cannot be made by other metals. 8 (a) In blast furnace, at the top is the zone of reduction. Here Fe2O3 is reduced to spongy iron by CO rising up. Fe2O3 +3CO⟶2Fe + 3CO2 9 (c) It is a fact. 10 (d) Cyanide process is used for obtaining silver. This process is also called as Mac Arthur and Forest process 11 (b) It is a fact. 12 (a) In Bessemer converter, copper sulphide is partially oxidised to cuprous oxide which further reacts with remaining copper sulphide to form copper and sulphur dioxide. Topic :- Isolation Elements Solutions
Cu2S + 2Cu2O→6Cu + SO2 13 (b) Beryl is 3BeO ∙ Al2O3 ∙ 6SiO2 . 14 (a) It is a fact. 15 (c) Lead present as impurity in the silver obtained by argentiferous lead is purified by cupellation. 16 (d) CaO, K2O cannot reduced by carbon reduction method 18 (c) The method is used for purification of Zr and Ti in which these metals on heating with I2 forms vapours of metal iodide which on decomposition gives pure metals. 19 (a) Mass number of uranium is highest, i.e., U 238 . 20 (b) Iron is made inactive or passive by oxidizing agents like conc. Nitric acid, chromic acid, acidified KMnO4, etc., the cause of this is the formation of a thin film of oxide on the surface of the metal.
ANSWER-KEY Q. 1 2 3 4 5 6 7 8 9 10 A. D A C D B B B A C D Q. 11 12 13 14 15 16 17 18 19 20 A. B A B A C D D C A B