Question

Give reasons
(a) Platinum, gold and silver are used to make jewellery.
(b) Sodium, potassium and lithium are stored under oil.
(c) Aluminium is a highly reactive metal, yet it is used to make utensils for cooking.
(d) Carbonate and sulphide ores are usually converted into oxides during the process of extraction.

Answer 1

(a) Platinum gold and silver are used to make jewellery because:
(i) they have bright and shiny surface
(ii) they are highly resistance to corrosion
(iii) they are highly malleable and ductile
(b) Sodium, potassium and lithium are very reactive metals. They react so vigorously with the oxygen of air that they catch fire it kept in the open. Sodium, potassium and lithium are stored under oil to protect them from the action of air (and moisture) and to prevent accidentaly fires.
(c) When highly reactive aluminium metla is exposed to air, the oxygen of air reacts with aluminium to form a thin but tough protectie layer of aluminium oxide on its surface. The presence of aluminium oxide layer makes the aluminium metal resistance to the action of aire and water. Due to its high resistance to corrosion and high heat conductivity, aluminium metal is used for making cooking utensils.
(d) The direct reduction of carbonate and sulphide ores to obtain metals is usually not possible. The carbonate and sulphide ores are first coverted into metal oxides because it is much easier to reduce metal oxides to obtain metals.