NCERT Solution for Class Tenth Science Chapter 2
Acids, Bases and Salts
Exercises Questions
Page No-18
Questions No-2
(a) NaCl (b) HCl (c) LiCl (d) KCl
A solution reacts with crushed egg-shells to give a gas that turns lime-water milky. The solution contains
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(b) 𝐻𝐶𝑙
The crushed egg-shells contains calcium carbonate [CaCO₃]. When 𝐻𝐶𝑙 solution reacts with this crushed egg-shells and produces carbon dioxide which turns lime – water milky.
CaCO₃ +𝐻𝐶𝑙 → CaCl₂ +H₂O+CO₂
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(b) 𝐻𝐶𝑙
The crushed egg-shells contains calcium carbonate [CaCO₃]. When 𝐻𝐶𝑙 solution reacts with this crushed egg-shells and produces carbon dioxide which turns lime – water milky.
(b) The solution contains HCl.
The solution that reacts with crushed eggshells to produce a gas that turns lime-water milky likely contains carbon dioxide (CO2). Here’s the explanation of the reaction:
Crushed eggshells contain calcium carbonate (CaCO3).
When an acid reacts with calcium carbonate, it produces carbon dioxide gas and a calcium salt. In this case, the acid responsible for the reaction is likely carbonic acid (H2CO3), which forms when CO2 dissolves in water (H2O).
The chemical reaction can be represented as follows:
CaCO3(s) + 2H2CO3(aq) → 2Ca(HCO3)2(aq) + CO2(g)
The carbon dioxide gas (CO2) generated in this reaction is then passed through lime-water (aqueous calcium hydroxide, Ca(OH)2). Lime-water is an alkaline solution of calcium hydroxide.
When carbon dioxide is bubbled through lime-water, it reacts with the calcium hydroxide to form calcium carbonate (CaCO3) as a white solid precipitate. This calcium carbonate is only sparingly soluble in water and is not dissolved, causing the lime-water to turn milky.
The milky appearance of lime-water confirms the presence of carbon dioxide in the gas that evolved from the reaction with crushed eggshells.