Give reason for the following :
(i) Metals conduct electricity.
(ii) Reaction of nitric acid with metals generally does not evolve hydrogen gas.
(iii) For making gold ornaments, 22 carat gold is preferred to 24 carat gold.

Explanation

(i) Metals conduct electricity because they have electrons which are free to move. They offer little resistance to the flow of current.
(ii) Reaction of metals with nitric acid does not evolve hydrogen gas. It is because `HNO_(3)` is a strong oxidising agent. It oxidises `H_(2)` to produce water and itself gets reduced to any of its oxides such as `N_(2)O`, NO or `NO_(2)`.
(iii) Pure gold is 24 carat and is very soft. Therefore, it is not suitable for making jewellery. it is alloyed with Cu or Ag to mae it hard. Generally, 22 carat gold is used for making ornaments, which contains 22 parts of pure gold and 2 parts of either Cu or Ag.