CG Board Class 10 Science Chapter 17 Solutions: Chemistry in Daily Life (दैनिक जीवन में रसायन) (2026-27)

(i) The chemical formula of baking soda is:**

(a) NaHSO₄

(b) Na_2CO₃

(c) NaHCO₃

(d) Na_2CO₃ · 10H_2O

• Correct Option: (c) NaHCO₃
• Explanation: Baking soda is chemically sodium hydrogencarbonate with formula NaHCO₃.

• Correct Option: (b) CaOCl₂
• Explanation: Bleaching powder (calcium oxychloride, CaOCl₂) acts as a disinfectant by releasing chlorine gas which kills germs in drinking water.

• Correct Option: (d) Super-cooled liquid
• Explanation: Glass is an amorphous solid that behaves structurally as a highly viscous, super-cooled liquid capable of extremely slow flow.

• Correct Option: (c) Absorbing water
• Explanation: Plaster of Paris absorbs water to recrystallize into hard gypsum (CaSO₄ · 2H_2O).

Soft Water:** Water that produces abundant lather quickly and easily when mixed with soap (e.g., rain water, distilled water).

• Hard Water: Water that takes a long time to produce lather with soap and forms an insoluble sticky precipitate (scum) due to dissolved salts of calcium or magnesium.

Causes of Hardness:** Hardness is caused by dissolved salts of calcium (Ca²⁺) or magnesium (Mg²⁺), such as hydrogencarbonates, sulphates, or chlorides.

• Types of Hardness: There are two types of hardness

1. Temporary Hardness: Caused by dissolved calcium or magnesium hydrogencarbonates [Ca(HCO₃)₂, Mg(HCO₃)₂]. It can be removed by boiling or by adding limewater.
2. Permanent Hardness: Caused by dissolved calcium or magnesium chlorides or sulphates (CaCl₂, MgCl₂, CaSO₄, MgSO₄). It cannot be removed by boiling.

At 4°C, liquid water reaches its maximum density of 1 g/mL, whereas ice at 0°C has a lower density of 0.9 g/mL. Consequently, ice floats on top of rivers and lakes. Because ice is a thermal insulator, it insulates the deeper water below from the freezing atmospheric cold. The water under the top ice layer remains liquid, allowing aquatic plants and animals to survive comfortably.

Baking powder is a solid dry mixture of baking soda (NaHCO₃) and tartaric acid.

When baking powder is mixed with water or heated during baking, the sodium hydrogencarbonate reacts with hydrogen ions (H^+) from tartaric acid

NaHCO₃ + H^+ → CO₂↑ + H_2O + Sodium salt of acid

The released carbon dioxide (CO₂) gas expands and bubbles up through the dough, making the cake rise and become soft and spongy.

Preparation Process:** Plaster of Paris is produced by heating gypsum (CaSO₄ · 2H_2O) at 100°C (373 K).

CaSO₄ · 2H_2O → [100°C] CaSO₄ · 1/2H_2O + 11/2H_2O

• Reason for Air-tight Storage: Plaster of Paris absorbs moisture from damp air and converts back into a hard solid mass of gypsum, ruining its setting utility. Thus, it must be stored in moisture-proof, air-tight containers.

Chemical Name:** Sodium carbonate decahydrate (Na_2CO₃ · 10H_2O).

• Three Main Raw Materials:

1. Sodium chloride (NaCl)
2. Ammonia (NH₃)
3. Carbon dioxide (CO₂) / Limestone (CaCO₃)

(i) Name the compound.**

(ii) Which gas is released when the compound is left out in open air? Give the balanced equation for this reaction.

(i)

(i) Compound Name: Bleaching powder (Chemical name: Calcium oxychloride, CaOCl₂).

(ii) Gas Released: Chlorine gas (Cl₂).

When exposed to air, it reacts with carbon dioxide gas to release chlorine

CaOCl₂(s) + CO₂(g) → CaCO₃(s) + Cl₂↑

(i) Write the chemical equation for the reaction which takes place on heating.**

(ii) Why is ‘X’ used as an antacid?

(i)

• Identification: ‘X’ is Sodium hydrogencarbonate (NaHCO₃); ‘Y’ is Carbon dioxide gas (CO₂).

(i) Chemical Equation on Heating:

2NaHCO₃ → [Heat] Na_2CO₃ + H_2O + CO₂↑

(ii) Reason for Antacid Use: ‘X’ (NaHCO₃) is a mild alkaline salt that neutralizes excess hydrochloric acid in the stomach to form salt, water, and CO₂, giving fast relief from hyperacidity.

(i) Necessary materials**

(ii) Substances that give or impart colour to glass

(iii) The chemical reaction taking place in tank furnace

(i)

(iii)

(i) Necessary Raw Materials: Silica (sand), Alkali metal carbonate (Na_2CO₃ or K_2CO₃), Divalent metal salt (limestone CaCO₃ or litharge PbO), and Cullets (broken glass pieces as flux).

(ii) Colouring Substances:

• Green: Chromium oxide (Cr_2O₃)
• Yellow: Cadmium sulphide (CdS)
• Red: Copper oxide (Cu_2O)
• Purple: Manganese oxide (MnO₂)
• Blue: Cobalt oxide (CoO)

(iii) Reactions in Tank Furnace (at 1400°C):

Na_2CO₃ + SiO₂ → Na_2SiO₃ + CO₂↑

CaCO₃ + SiO₂ → CaSiO₃ + CO₂↑

Na_2SiO₃ + CaSiO₃ + 4SiO₂ → Na_2O · CaO · 6SiO₂ (Glass)

The raw materials for cement production are limestone (CaCO₃), clay, and gypsum.

1. Pulverization & Mixing: 3 parts limestone and 1 part clay are finely pulverized, mixed, and fed into a rotary kiln maintaining temperatures between 1100-1800°C.
2. Decomposition: At 1100°C, limestone decomposes to quicklime

CaCO₃ → [1100°C] CaO + CO₂↑

1. Synthesis Reactions (1400-1500°C): Calcium oxide reacts with silica, alumina, and iron oxide present in clay to form silicates and aluminates

• 2CaO + SiO₂ → 2CaO · SiO₂ (Dicalcium silicate)
• 3CaO + SiO₂ → 3CaO · SiO₂ (Tricalcium silicate)
• 3CaO + Al_2O₃ → 3CaO · Al_2O₃ (Tricalcium aluminate)
• 4CaO + Al_2O₃ + Fe_2O₃ → 4CaO · Al_2O₃ · Fe_2O₃ (Tetracalcium alumino ferrite)

1. Clinker Formation: The resulting fused pebble-like mass is called clinker.
2. Grinding with Gypsum: Clinker is cooled, blended with 2-3\% gypsum (CaSO₄ · 2H_2O), and ground into fine cement powder.

Soap molecules are sodium or potassium salts of long-chain fatty acids (RCOOM). When soap is dissolved in water, it ionizes into carboxylate ions (RCOO^-) and metal ions (M^+).

The carboxylate ion (RCOO^-) consists of two parts

1. Hydrocarbon Tail (R): Non-polar, hydrophobic (water-repelling), and lipophilic (attracted to oil/dirt).
2. Carboxylate Head (COO^-): Polar, hydrophilic (water-attracted), and ionic.

Formation of Micelles: When oily dirt is present in water, soap molecules align themselves radially around the oil drop. The hydrophobic hydrocarbon tails stick inside the oil droplet, while the hydrophilic polar heads (COO^-) face outward into the water, forming a spherical structure called a micelle. These micelles suspend the dirt in water as a colloid, allowing it to be easily washed away.