(i) Consider the following metals : K, Ca, Al, Cu, Ag, Fe Select from the above metals, a metal which I.…
(i) Consider the following metals :
K, Ca, Al, Cu, Ag, Fe
Select from the above metals, a metal which
I. does not react with oxygen even at high temperature.
II. reacts with oxygen at ordinary temperature and forms a protective oxide layer which prevents the metal from further oxidation.
III. catches fire when kept in the open.
IV. does not burn in oxygen but the hot metal is coated with a black coloured oxide layer.
(ii) What are amphoteric oxides ? With the help of balanced chemical equations show that aluminium oxide is an amphoteric oxide.
(iii) What are alkalis ? Give one example.
Solution
(a) (i) (I) Ag, (II) Al, (III) K, (IV) Cu
(ii) Metal oxides which react with both acids as well as bases to produce salts and water are called amphoteric oxides.
Al2O3 + 6HCl → 2AlCl3 + 3H2O
Al2O3 + 2NaOH → 2NaAlO2 + H2O
(Do not deduct marks if equation is not balanced)
(iii) Water soluble bases are called Alkalis.
NaOH / KOH / Sodium Hydroxide / Potassium Hydroxide
(any one)