Question

EXPLAIN with reason –

(a) Reactivity of aluminium decreases in HNO3?

(b) Aluminium is highly reactive yet it is used to utensils ?

(c) platinum/gold used for jewellery?

(d) shiny surface of metals tarnished or have dull appearance for keeping long

time? (e) copper used for hotwater tanks not steel?

(f) non-metals do not displace hydrogen from dil acids

(i) Na/K are kept in kerosene oil ?

(j) Copper vessels are cleaned with lemon juice? ​

Answer 1

Answer:

When Al is dipped in nitric acid a layer of aluminium oxide is formed on the metal. This happens because nitric acid is a strong oxidizing agent. The layer of aluminium oxide prevents further reaction of aluminium and due to this reactivity of Al decreases.

Explanation:

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Answer 2

Answer:

1. because HNO3 is a oxidizing agent and form aluminium oxide with it which is lower in reactivity series so, this happen
2. because aluminium is low coast and react with oxygen in large time and then it react with hot water.so it is used
3. it not react
4. because copper dont react with hot water
5. because non metals is reciver not doner of electrone
6. it is highly reactive
7. copper react with oxygen and form coating and metallic oxide is basic in nature and lemon contain citric acid so this can remove the oxygen layer