Question

Give reasons for the following:
(A) Aluminium foils are used to wrap food items.
(B) Immersion rods for heating liquid are made up of metallic substances.
(C) Copper cannot displace zinc from its salt solution.
(D) Sodium and potassium are stored in kerosene.

Answer 1

All the alkali metals are highly reactive so they are stored under oil to prevent them coming into the contact of water and air.
Highly active metals are placed above hydrogen and less active metal are placed below the hydrogen in the electrochemical series.

Complete answer:
(A)Aluminium has a high tensile strength and it is very light in weight. Aluminium metal is very soft malleable and ductile so it can be beaten into sheets and converted into wrapping foils. Aluminium metal generally does not react with food products.
(B)Due to the presence of loosely held valence electrons which are free to move in a metal structure, hence all the metal is a good conductor of heat and electricity. Hence, immersion rods are made up of metallic substance which shows high thermal conductivity.
(C) An active metal displaced the metal ion listed below the electrochemical series from its salt solution, but not above metal. Since zinc metal is more active than copper metal, hence copper cannot displace zinc from its salt solution.
(D) Sodium and potassium are highly reactive metals. These metals get tarnish in air due to the formation of oxide at their surface. If sodium and potassium were not stored under kerosene or paraffin oil they would corrode very rapidly.

Note:
Zinc metal is able to displace copper ions from it solution while silver cannot displace the copper ion from it solution because silver atom is listed below the copper atom in electrochemical series.