Question

(a) Why are alkali metals kept in kerosene oil?
(b) What is
(i) basic lead carbonate and
(ii) brown powder deposit on iron?
(c) Why is hydrogen kept in the metal activity series? [4 MARKS]

Answer 1

a) 1 Mark
b) 2 Marks
c) 1 Mark

(a) Alkali metals are very reactive. They are kept in kerosene oil to prevent them from exposure to air and moisture as they readily react with $O_2,C{O}_2,H_{2}O$ present in air, even at room temperature.

(b) A white deposit is formed on the surface of lead by its reaction with moist air. It is a mixture of lead hydroxide and lead carbonate and called basic lead carbonate. Its chemical formula is $Pb(OH{)}_2.2PbC{O}_3$.
Brown powder deposit on iron in moist air is rust or hydrated iron(III) oxide, $F{e}_2{O}_3.x{H}_{2}O$.

(c) Hydrogen is kept in the metal activity series because like metals, it also forms a positive ion.
$H-e^{-}\to H^{+}$