(a) (i) Describlea methodfor refiningnickel. (ii)Whygroup18elementsare calledinertgases ?Writethe generalelectronicconfigurationof group18 elements. (b) (i) Givethe usesof helium. (ii) Ni(II) compounds are morestablethan Pt(II) compound.Givereason.

(a) (i) Describlea methodfor refiningnickel. (ii)Whygroup18elementsare

1.	(a) (i) Describlea methodfor refiningnickel. (ii)Whygroup18elementsare calledinertgases ?Writethe generalelectronicconfigurationof group18 elements. (b) (i) Givethe usesof helium. (ii) Ni(II) compounds are morestablethan Pt(II) compound.Givereason.
Answer» Solution :(i) Theimpure nickelis heatedin a streamof carbon monoxideat around350 k.The nickelreactswith thecoto fromhiglyvolaticnickel tetracarbony. The solid impuritiesare leftbehind. `Ni(s)+4CO (G) to Ni (CO)_(4) (g)` Onheating the nickeltetracarbonyl around 460 k the complexdecomposesto givepuremetal . (ii)the elementsof group-18havecompletyfilleds and porbitalhencetheyare morestableand haveleastreactivity.Thereforegroup -18elementsare calledinertgases. (b)(i) Usesof helium 1. Heliumand oxygenmixtureis usedby diversin placeof AIR oxygenmixture . This preventsthepainfuldangerousconditioncalledbends. 2.Heliumis usedto provideinertatmosphere inelectricweldingof metals 3. Heliumhas lowestboilingpointhenceusedin cryogenic . 4. If is muchlessdenserthan airandhenceusedforfillingairballons. (ii) Theionisationenthalpyvaluescan beusedto predicthe themodymicstabilityoftheircompound . For Nickel .` Le_(1)+ LE_(2)= 737+ 1753` Sincethe energyrequiredto from`Ni^(2+)` is lessthan that `Pr^(2+)` Ni (II)compoundsare thermodynamicallymore stablethantP (ii)compounds.