state the reason for the following
(1) Aluminum oxide is called an amphoteric.
(2) An iron strip dipped in a blue copper sulphate solution turns the blue solution pale green.
(3) Hydrogen gas is not evolved when most metals react with nitric acid.
(4) calcium does not occur in free state in nature.
(5) Sodium or potassium metals are kept immersed under kerosene.
Answers
Answer:
--1. oxide is known as 'amphoteric oxide' due to its reaction with both acids and bases.
---2.The iron strip which dipped in the "blue copper sulphate solution" turned into the "blue solution pale green". This is due to the fact that there is "formation of iron sulphate" takes place inside solution.
----3.When metals reacts with the nitric acid, it is oxidised by nitrate ion and not by hydrogen ion.
---4.Calcium doesn't occur in any 'free state' in nature, because it is "highly reactive in nature".
---5.Sodium and potassium metals are reactive and act violently in presence of air.
Explanation:
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Answer:
(1) Aluminium oxide is called as amphoteric oxide because it reacts with acid as well as base.
(2) Iron being more reactive than copper displaces copper from its solution and form iron sulphate solution and hence turn the blue solution pale green.
(3) It is because HNO3 is a strong oxidising agent. It oxidises the H2 produced to water and itself get reduced to any of the nitrogen oxides
(4) it does not occur in free state because it is highly reactive
(5) sodium and potassium reacts vigorously that they even catch fire if kept in open. Hence, to protect them and to prevent accidental fire they are kept immersed in kerosene oil