Question

a) When calcium metal is added to water, the gas evolved does not etch fire but the same gas evolved on adding potassium metal to water catches fire. Explain why ?
(b) Name a metal for each case :
(i) it displaces hydrogen gas from nitric add.
(ii) it does not react with any physical state of water.
(iii) It does not react with cold as well as hot water but reacts with steam.


CBSE Class X Science LA (5 Marks)

Answer 1

a-because in the case of calcium heat evolved is very less which is not sufficient to burn hydrogen but in the case of potassium heat evolved is high which leads to burning of hydrogen
b-3-iron(Fe)

Answer 2

A):-

When calcium metal is added to water then hydrogen is evolved in very less amount while when sodium metal is added to water, again hydrogen gas is evolved but in large amount. So the gas evolved in 1st case is not sufficient to burn or catch fire but the gas evolved in 2nd case may catch fire or burn since it is produced in very large amount.

B):-

i) Sodium metal being more reactive can displace hydrogen gas from nitric acid.

ii) Gold, silver and platinum are metals which do not react with any physical state of water.

iii) Iron is a metal which do not react with cold or hot water but it reacts with steam.

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