CBSE Class 10 Science 2023 Outside Delhi Set 1

Question : 28

Total: 39

(a) A substance ' X ' is used as a building material and is insoluble in water. When it reacts with dil. HCl, it produces a gas which turns lime water milky.
(i) Write the chemical name and formula of ' X '.
(ii) Write chemical equations for the chemical reactions involved in the above statements.
OR
(b) A metal ' M ' on reacting with dilute acid liberates a gas ' G '. The same metal also liberates gas ' G ' when reacts with a base.
(i) Write the name of gas ' G '
(ii) How will you test the presence of this gas?
(iii) Write chemical equations for the reactions of the metal with (1) an acid and (2) a base.

Solution:

(a) (i) Substance X is Calcium Carbonate (CaCO3) or limestone.
(ii)

CaCO3(s)

Calcium carbonate‌(X)

2‌HCl(aq)

dil

→

CaCl2(aq)

Calcium chloride

+H2O(l)+CO2↑

Carbon dioxide gas (CO2) evolved turns lime water milky.

‌CO2+‌

Ca(OH)2(aq)

‌ (lime water) ‌

→

CaCO3(s)

‌ milky ‌

+‌H2O(l)

(b) (i) The gas G is hydrogen gas.
(ii) A characteristic test for hydrogen (H2) gas can be performed by bringing a burning candle near the source of hydrogen. On doing so, hydrogen gas burns with a squeaky pop sound.
Hydrogen gas is recognised by the 'pop' when it burns. The 'pop' is the sound of a small explosion.
(iii) Zinc metal, reacts with both acid and base to produce hydrogen gas.

‌

Zn(s)

Zinc

2‌NaOH(aq)

‌ Sodium hydroxide

‌ Heat ‌

→

‌

Na2ZnO2(aq)

‌ Sodium zincate

H2(g)↑

Hydrogen

Zn(s)+2‌HCl(aq)

Hydrochloric acid(dil.)

→

ZnCl2(aq)+H2(g)↑

Zinc chloride

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