Question

(d)
Give a reason for each of the following:
(1)
Noble gases do not combine with other elements to form molecules.
(ii) Dilute nitric acid cannot be used in the preparation of hydrogen.
(iii) Hydrogen although lighter than air, is not collected by the downward
displacement of air.
(iv) Anhydrous calcium
chloride turns into a colourless solution when
exposed to air.
(v) Metals form positive ions.​

Answer 1

Explanation:

i) Noble gases contain paired number of electrons which are not involved in the reaction hence they do not combine and they can be made to combine at some critical temperature and pressure you'll get to know about it when you are in 12 th

ii) Nitric acid not used in the laboratory preparation of hydrogen. This is because nitric acid is a strong oxidising agent, and oxidises hydrogen gas to convert it into the water. ... sulphuric acid and dilute hydrochloric acid do not oxidise hydrogen into water hence preferred for the preparation of hydrogen gas

iii) Even though hydrogen is lighter than air it is not collected by downward displacement of air because of these reasons: Hydrogen gets oxidised when it is exposed to oxygen which makes it burn with a pale blue flame and the residue is water. ... Hydrogen is lighter than air but mixes with air

iv) calcium carbide is a deliquescent substance it absorb water from the atmosphere when exposed to air. If anhydrous calcium chloride is exposed in the air it will also water from the atmosphere and turns into a colourless solution

V) metals form positive ions bcz they are electron donors

Hope it helps ♥

Answer 2

Here is your answer :

1)Noble gases do not combine with other elements to form molecules.

Ans : Because noble gases are stable .. their Valence shell have 8 electrons expect helium (He).They are following octet rule ...so, they do not combine..

2)Dilute nitric acid cannot be used in the preparation of hydrogen.

Ans: Because nitric acid (HNO3) are Oxidizing agent. so, it turn hydrogen into water.

3) Hydrogen although lighter than air, is not collected by the downward displacement of air.

Ans : Because it form water , when exposed to air..

4) Anhydrous calcium chloride turns into a colourless solution when exposed to air.

Ans : Because when calcium chloride exposed to air it absorb water and turn into colourless solution..

5) Metals form positive ions.

Ans : Because metals are good reducing agent.. metals donate one or more electrons and form cation or positive charge....

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