Title DPP-1 SOLUTION.pdf ✅

CLASS : XIth SUBJECT : CHEMISTRY DATE : DPP No. : 1 1 (a) CO + S Heat COS (Carbonyl sulphide) 3 (a) Felspar is an ore of Al. Its composition is KAlSi3O8 or K2O.Al2O3.6SiO2. 4 (c) Thermite is the mixture of Fe2O3 and Al. Due to great affinity of aluminium towards oxygen, it readily combines with oxygen. Hence, Goldshmidt used Al to reduce metal oxides in extraction. In thermite, the ratio of Fe2O3 and Al is taken 3:1 by weight. Fe2O3 +2Al→2Fe + Al2O3 (2 × 56 + 3 × 16 = 160) (2 × 27 = 54) 5 (b) BI3 > BBr3 > BCl3 > BF3 This order can be easily explained on the basis of the tendency of the halogen atom to back donate its lone pair of electrons to the empty p-orbital of the boron atom through pπ ― pπ bonding. 6 (b) Alum acts as coagulating agent, so it is used to purify water and separate mud from it. 7 (d) Al is used as reducing agent in thermite process. Cr2O3 + 2Al→2Cr + Al2O3 8 (c) Diborane possesses four B—H covalent bonds and two three centred (two electrons) B— H—B or hydrogen bridge bonds. These bonds are also known as banana bonds. 9 (b) The structure of silicates has been found with the help of X-ray diffraction technique. All silicates have tetrahedral SiO 4― 4 ion as a basic building unit i.e., all silicates are composed of many units. Tetrahedral shape of [SiO4 ] 4― ion is due to sp 3 -hybridisation of Si-atom. Sheet silicates are formed when three oxygen atoms (bridging O-atoms) of each (SiO4 ) 4― unit are shared. Hence, the general formula of sheet silicates is (Si2O5 ) 2n― Topic :-THE P-BLOCK ELEMENTS-1 Solutions
10 (a) Pb reacts with dilute HNO3 and produces NO. 3Pb + 8HNO3→3Pb(NO3 )2 + 2NO + 4H2O dil. 11 (a) It is a fact. The alloy is called Rolled gold. 13 (a) Lamp black is used for all these purposes. Carbon black is used in making tyres. Bone black is used for decolourisation of sugar. 14 (b) It is a fact. 15 (c) 2Al + Cr2O3⟶Al2O3 + 2Cr ; ∆H = ―ve Reductant Oxidant 16 (c) B2H6 + 6H2O⟶2H3BO3 + 6H2 17 (b) The main impurity in red bauxite is ferrite (Fe2O3 ) and the main impurity in white bauxite is silica (SiO2 ). 18 (d) Al shows maximum covalency of six whereas as boron shows four. 19 (d) Metals forming coloured bead can be identified by boras bead test. 20 (d) Asbestos can withstand red hot flames without any damage. - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
ANSWER-KEY Q. 1 2 3 4 5 6 7 8 9 10 A. A A A C B B D C B A Q. 11 12 13 14 15 16 17 18 19 20 A. A A A B C C B D D D