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1.	In the exteraction of copper from its sulphide ore, the metal is fanally obtained by the reduction of caprous oxide withA. copper (I) sulphide `(Cu_(2)S)`B. sulphur dioxide `(SO_(2))`C. iron sulphide (FeS)D. carbon monoxide (CO)
Answer» Correct Answer - A In the extraction of copper from its sulphide ore, when ore is subjected to roasting, some of it is oxidised to `Cu_(2)O` which reacts with the remaining `Cu_(2)S` (sulphide ore) to give copper metal. `2Cu_(2)S + 3O_(2) rarr 2Cu_(2)O + 2SO_(2)uarr` `2Cu_(2)O + Cu_(2)S rarr 6Cu + SO_(2) uarr` In this process `Cu_(2)S` behaves as reducing agent.

2.	The method of zone refining of metals is based on the principle of :A. greater noble character of the solid metal than that of the impurityB. greater solubility of the impurity in the molten state than in the solidC. greater mobility of the pure metal than that of impurityD. higher melting point of the impurity than that of the pure metal
Answer» Correct Answer - B The method of zone refining of metals is based on the principle of greater solubility of the impurity in the molten state than in the solid. Elements which are used as semiconductors like Si, Ge, Ga, etc, are refined by this method. Gallium arsenide and indium antimonide (also used as semiconductor) are also refined by this method.

3.	Elemental `Si` in to be used as a semicondictor is parified byA. heating under vacuumB. floatationC. zone refiningD. electrolysis
Answer» Correct Answer - C Zone refining is used for metals which are required in very purity. Semiconductor grade silicon is purified by this method (Si, Ge).

4.	Calcium is obtained by theA. roasting of limestoneB. electrolysis of solution of calcium chloride in `H_(2)O`C. electrolysis of molten anhydrous calcium chlorideD. reduction of calcium chloride with carbon
Answer» Correct Answer - C Calcium is obtained by electrolysis of molten anhydrous calcium chloride

5.	Which of the following is not a mineral of iron?A. MalachiteB. CassiteriteC. PyrolusiteD. Magnetite
Answer» Correct Answer - D `{:("Mineral","Chemical composition"),("Malachite",CuCO_(3).Cu(OH)_(2)),("Cassiterite",SnO_(2)),("Pyrolusite",MnO_(2)),("Magnetite",FeO_(4)):}` Thus, magnetite is a mineral of iron.

6.	Calgon used as water softener isA. `Na_(2)[Na_(4)(PO_(3))_(6)]`B. `Na_(4)[Na_(2)(PO_(3))_(6)]`C. `Na_(4)[Na_(4)(PO_(4))_(5)]`D. `Na_(4)[Na_(2)(PO_(4))_(6)]`
Answer» Correct Answer - A Sodium polymetaphosphate is used to remove the permanent hardness of water. The commercial name of sodium polymetaphosphate is calgon meaning calcium gone. The molecular formula of calgon is `Na_(2)[Na_(4)(PO_(3))_(6)]`.

7.	In the exteraction of copper from its sulphide ore, the metal is fanally obtained by the reduction of caprous oxide withA. iron (II) sulphideB. carbon monoxideC. copper (I) sulphideD. sulphur dioxide
Answer» Correct Answer - C `Cu_(2)S + 2Cu_(2)O rarr 6Cu + SO_(2)uarr`

8.	Aluminum is exteracted from alumine `AI_(2)O_(3)` by electrolysis of a molten mixture of :A. `Al_(2)O_(3) + HF + NaAlF_(4)`B. `Al_(2)O_(3) + CaF_(2) + NaAlF_(4)`C. `Al_(2)O_(3) + Na_(3)AlF_(6) + CaF_(2)`D. `Al_(2)O_(3) + KF + Na_(3)AlF_(6)`
Answer» Correct Answer - C Alumina, `Al_(2)O_(3)` is a bad conductor of electricity and has very high melting point, so before subjecting to electrolysis, it is mixed with fluorspar `(CaF_(2))` and cryolite `(Na_(3)AlF_(6))`, which lower its melting point and make it more conducting. Mainly `CaF_(2)` and `Na_(3)AlF_(6)` are mixed with `Al_(2)O_(3)` for converting `Al_(2)O_(3)` in molten state.

9.	Roasting of sulphides gives the gas X as a by product. This is a colourless gas with choking smell of burnt sulphur and causes great damage to repiratory organs as a result of acid rain. Its aqueous solution is acidic, acts as reducing agent and its acid has never been isolated. The gas X is :-A. `H_(2)S`B. `SO_(2)`C. `CO_(2)`D. `SO_(3)`
Answer» Correct Answer - B `SO_(2)` gas is obtained when any sulphide ore is roasted. `2M_(2)S+3 O_(2)overset(Delta)rarr 2M_(2)O + 2 SO_(2)` This gas exhibits all the characteristics that are given in the question.

10.	The reaction of `H_(2)O_(2)` with hydrogen sulphide is an example of ………… reaction.A. additionB. oxidationC. reductionD. acidic
Answer» Correct Answer - B When `H_(2)O_(2)` is reacted with hydrogen sulphide `(H_(2)S)`, it form S and water. In this reaction `H_(2)S` is oxidised to sulphur. `H_(2)O_(2)` act as oxidising agent. `H_(2)O_(2) + H_(2)S rarr S + 2 H_(2)O`

11.	Which one of the following is the major impurity in pig iron?A. SiliconB. OxygenC. SulphurD. Graphite
Answer» Correct Answer - D Graphite produces impurity in pig iron. Pig iron contains 2.5 to 5.0% of carbon.

12.	Match items of Column I with the items of Column II and assign the correct code: `{:(ColumnI,ColumnII),((A)"Cyanide process",(1)"Ultrapure Ge"),((B)"Froth Floatation Process",(2)"Dressing of"ZnS),((C)"Electrolytic reduction",(3)"Extraction of Al"),((D)"Zone refining",(4)"Extraction of Au"),(,(5)"Purification of Ni"):}`A. `{:("A","B","C","D"),(2,3,1,5):}`B. `{:("A","B","C","D"),(1,2,3,4):}`C. `{:("A","B","C","D"),(3,4,5,1):}`D. `{:("A","B","C","D"),(4,2,3,1):}`
Answer» Correct Answer - D A - 4, B - 2, C - 3, D - 1 • Cyanide process It is a metallurgical technique for extracting Au (gold) from low grade ore by converting the Au to a water-soluble coordination complex. • Froth floatation process This process is used for dressing of sulphide ore, i.e. ZnS. • Electrolytic reduction This process is used for extraction of Al which is carried out in a steel tank lined inside with graphite. Here, graphite serves as cathode. The electrolyte consists of alumina dissolved in fused cryolite `(Na_(3)AlF_(6))` and fluorspar `(CaF_(2))`. • Zone refining This process is used for ultra pure Ge element An ingot of Ge is first purified by zone refining. Then a small amount of antimony is placed in the molten zone which is passed through the pure Ge with the proper choice of rate of heating and other variables.