Q9 of 400 Page 131

What is aqua-regia ? Name two special metals which are insoluble in comman reagents but dissolve in aqua-regia.

A freshly prepared mixture of one part of concentrated nitric acid and 3 parts of concentrated hydrochloric acidis known as aqua-regia. The two special metals which are insoluble in comman reagents but dissolve in aqua-regia are Gold and Platinum.

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7 From amongst the metals sodium, calcium, aluminium, copper and magnesium, name the metal:

(i) which reacts with water only on boiling, and


(ii) another which does not react even with steam.

 8 What changes in the colour of iron nails and copper sulphate do you observe after keeping the iron nails dipped in copper sulphate solution for about 30 minutes? 10 Give the names and formulae of (a) two acidic oxides, and (b) two basis oxidics. 11 What name is given to those metal oxides which show basis as well as acidics behavior ?