Question 12:
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
(a) Platinum, gold, and silver are used to make jewellery because they are very
lustrous. Also, they are very less reactive and do not corrode easily.
(b) Sodium, potassium, and lithium are very reactive metals and react very vigorously
with air as well as water. Therefore, they are kept immersed in kerosene oil in
order to prevent their contact with air and moisture.
(c) Though aluminium is a highly reactive metal, it is resistant to corrosion. This is
because aluminium reacts with oxygen present in air to form a thin layer of
aluminium oxide. This oxide layer is very stable and prevents further reaction of
aluminium with oxygen. Also, it is light in weight and a good conductor of heat.
Hence, it is used to make cooking utensils.
(d) Carbonate and sulphide ores are usually converted into oxides during the process
of extraction because metals can be easily extracted from their oxides rather than
from their carbonates and sulphides.
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