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GOLDCREST HIGH-LATUR ON THE WINGS OF EXCELLENCE CYCLE TEST-08 SUBJECT:-CHEMISTRY GRADE-10 DATE: 06-12-2016 MARKS: 40 TIME: 1 HOURS --------------------------------------------------------------------------------------------------------------------------------------------------------------- General Instructions Answers to this paper must be written on the paper provided separately. You will not be allowed to write during the first 15 minutes. This time is to be spent in reading the question paper. The time given at the head of the paper is the time allotted for writing the answers. The intended marks of questions or parts of questions are given in brackets [ ]. (METALLURGY ) Question-01 (a) Name : (i) A carbonate not decomposed by heat (ii) A green carbonate which turns black on heating. (iii) A non-metal which that has metallic luster and sublimes on heating. (iv) A metal which has low melting point. (v) A metal which on exposure to air forms an oxide (vi) A metal that displaces hydrogen from steam (vii) A metal whose carbonate does decompose on heating (viii) A metal which displaces iron from ferric oxide (ix) An alloy of iron used in electromagnets. (x)A non-metallic element which forms acidic and neutral oxides (xi) A dense non-metal (xii) Two non-metals with high boiling point (xiii) Two neutral oxides (xiv) Three metallic oxides that can not be reduced by hydrogen (b) Giving one example ,explain the following terms used in the metallurgy: [7] [5] (i)Calcination (ii) Roasting (iii) Gangue (iv) Flux (v) Slag (c) For each substance listed below explain its significance in the extraction of aluminium: [5] (i) Bauxite (ii) Sodium Hydroxide (iii) Cryolite (iv) Fluorspar (v) Graphite (d) Write the composition and uses of the following alloys mentioned below: Steel ,Duralumin, Brass, Bronze ,Fuse Metal ,Solder(Fuse Metal) [6] (e) Give reasons: (i) Aluminium is more active than iron,yet there is less corrosion of aluminium when both are expoed to air (ii) Haematite is preferred to iron pyrites as the ore for use in the extraction of iron. (iii) Food is generally stored in vessels made of zinc (iv) Aluminium transmission wires are preferred to copper transmission wires (v) Zinc is more electropositive than iron yet it is used to cover iron to prevent rusting of iron. (vi) Why the electric bulb glows up once the concentration of the aluminium falls down in the elctrolytic chamber in the Hall s Heroult process. (vii) The anode is replaced periodically in the Hall s Heroult process. (viii) Pure alumina is not directly electrolysed in the Hall s Heroult process.Why? [8] Question-02 (a) Complete the table [4] NAME OF THE PROCESS ELECTROLYTE USED AND ITS DISSOCIATION REACTION REACTION AT CATHODE REACTION AT ANODE PRODUCT AT CATHODE PRODUCT AT ANODE 1. HALL S HEROULT PROCESS 2. HOOPE S PROCESS (b) How is pure alumina is obtained from the ore of aluminium. Give relevant chemical equations? [1] (c) What is Thermite Welding? Why is it used in aluminothermy? [1] (d) What is Amalgam? Why are alloys are preferred to pure metals? [1] (e) What is Levigation and Pulverisation ? [1] (f) What is Weeping of Metals ? In what ways is it different from Tarnishing of Metals [1] ---------------------------------------------------------------------------------------------
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