Question

Give reasons for the following.(
a) Aluminium foils are used to wrap food items.
(b) Immersion rods for heating liquids are made up of metallic substances.
(c) Copper cannot displace zinc from its salt solution.
(d) Sodium and potassium are stored in kerosene
(e)Red litmus paper turns blue in presence of Iron oxide.

Answer 1

1. Aluminium foils are used to wrap food items because aluminium metal is malleable. Therefore, it can be beaten into thin foils.Concept insight: metals are malleable.
2. Immersion rods for heating liquids are made up of metallic substances because metals are good conductors of heat and electricity. The immersion rod needs an electric supply to get heated and in turn to heat liquids.
3. Copper is less reactive than zinc. This can be confirmed from the electrochemical or activity series in which Zn has a lower reduction potential than Cu. This means Zn is more reactive than Cu . This is the reason, copper cannot displace zinc from its salt solution.
4. Sodium and potassium are highly reactive metals. If kept in open, they readily react with oxygen in the atmosphere. The reaction is so quick that sodium and potassium easily catch fire when exposed to air. To prevent accidental fire, they are stored in kerosene.
5. Suspension of rust is basic in nature and hence turns moist red litmus blue.

Answer 2

Answer:

A. Aluminium metal has high malleability and ductility

B. Because, Metals are good conductors of heat and electricity

C. Zinc is more reactive than copper, zinc can displace copper from its salt solution

D. Sodium and Potassium are highly reactive metals and react vigorously with the oxygen, carbon dioxide and moisture present in the air such that it may even cause a fire, to prevent from explosion, Sodium is kept immersed in kerosene because Sodium doesn't react with kerosene

E. Red Litmus paper turns to blue in case, because Iron Oxide is Basic in Nature

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