CG Board Class 10 Science Chapter 11 Solutions: Chemistry of Non-Metals (अधातुओं का रसायन) (2026-27)

(i) The solution in water of which of the following will be acidic:**

• (a) Na_2O
• (b) CO₂
• (c) MgO
• (d) H_2O

(b) CO₂

Explanation: Carbon dioxide (CO₂) is a non-metallic oxide that dissolves in water to form carbonic acid (H_2CO₃), turning blue litmus red. Na_2O and MgO form basic solutions, while H_2O is neutral.

Answer: (a) Sodium

Explanation: Sodium is a metal that exists in a single crystalline form and does not show allotropy. Oxygen (O₂, O₃), Sulphur (rhombic, monoclinic), and Phosphorus (white, red, black) exhibit allotropy.

Answer: (d) Arsenic

Explanation: Arsenic (As) lies along the diagonal zig-zag line of the periodic table and exhibits intermediate properties between metals and non-metals.

Answer: (c) Their outermost shell is full

Explanation: Noble gases have a complete octet (or duplet for He) in their outermost valence shell, rendering them stable and chemically unreactive.

Answer: (b) Oxygen

Explanation: Thermal decomposition of potassium permanganate (KMnO₄) yields oxygen gas: 2KMnO₄ → [Δ] K_2MnO₄ + MnO₂ + O₂↑.

(i) The most electronegative element is …………….. (chlorine/ fluorine).**

(ii) Carbon is ………… (more/less) reactive as compared to oxygen.

(iii) Non-metals are found at the …………….(right/ left) side of the periodic table.

(iv) ……………….. (hydrogen/ nitrogen) gas is obtained when granulated zinc is reacted with dilute acid or alkali.

• (i) fluorine
• (ii) less
• (iii) right
• (iv) hydrogen

1. Hydrogen (H₂):

• Chloride: H₂(g) + Cl₂(g) → 2HCl(g)
• Oxide: 2H₂(g) + O₂(g) → 2H_2O(l)

1. Phosphorus (P₄):

• Chloride: P₄(s) + 6Cl₂(g) → 4PCl₃(l)
• Oxide: P₄(s) + 5O₂(g) → P_4O₁₀(s)

1. Sodium (Na):

• Chloride: 2Na(s) + Cl₂(g) → 2NaCl(s)
• Oxide: 4Na(s) + O₂(g) → 2Na_2O(s)

1. Magnesium (Mg):

• Chloride: Mg(s) + Cl₂(g) → MgCl₂(s)
• Oxide: 2Mg(s) + O₂(g) → 2MgO(s)

Nitrogen and hydrogen react to produce Ammonia gas (NH₃) via Haber’s Process.

• Balanced Chemical Equation:

N₂(g) + 3H₂(g) ⇌ [450°C-500°C, 200 atm / Fe catalyst, Mo promoter] 2NH₃(g)

• Reaction Conditions:

1. Temperature: 450°C – 500°C
2. Pressure: 200 atm (high pressure)
3. Catalyst: Finely divided Iron (Fe)
4. Promoter: Molybdenum (Mo) (increases catalyst efficiency)

Yes, we agree with this statement.** Hydrogen shows dual characteristics resembling both Group 1 alkali metals and Group 17 halogens

1. Resemblance with Group 1 (Alkali Metals):

• Electronic configuration: Contains 1 electron in the outermost shell (1s¹).
• Electropositive character: Can lose 1 electron to form a monovalent positive ion (H^+).
• Combines with non-metals (oxygen, sulphur, halogens) to form compounds like H_2O, H_2S, HCl.

1. Resemblance with Group 17 (Halogens):

• Requires 1 electron to complete its nearest noble gas configuration (He).
• Electronegative character: Can gain 1 electron to form a hydride ion (H^-), forming ionic hydrides (NaH, CaH₂) with active metals.
• Diatomic molecule: Exists as a diatomic gas (H₂), similar to F₂, Cl₂, Br₂.
• Non-metallic nature and high ionization energy.

Helium, neon, argon, krypton, xenon, and radon belong to Group 18 of the periodic table. They are called inert gases (or noble gases) because their outermost valence shells are completely filled with 8 electrons (octet completed; Helium has a duplet of 2 electrons). Due to this fully-filled stable electronic configuration, they have zero valency and no chemical affinity to gain, lose, or share electrons, remaining unreactive under normal conditions.

(a) Heat Production on Combustion:**

• Hydrogen gas has a very high calorific value and burns cleanly in oxygen to release immense thermal energy without emitting carbon pollutants

2H₂(g) + O₂(g) → 2H_2O(g) + Energy

• Industrial uses: Oxy-hydrogen flames (2800°C) are used for welding and cutting metals. Liquid hydrogen is used as high-energy rocket fuel and in fuel cells to generate electrical energy and heat.
• (b) Reaction with Vegetable Oils (Hydrogenation):
• Unsaturated organic compounds in vegetable oils contain carbon-carbon double bonds (C=C). When hydrogen gas is passed through liquid vegetable oil at 150°C-200°C in the presence of a Nickel (Ni) catalyst, the double bonds are converted into single bonds (C-C).
• Industrial process:

Unsaturated Vegetable Oil + H₂ → [Ni Catalyst / 150°C-200°C] Saturated Vegetable Fat (Vanaspati Ghee)

• This process is called Hydrogenation of Oils and is used to manufacture solid vegetable ghee from liquid oils.

When dark purple crystals of Potassium Permanganate (KMnO₄) are heated, thermal decomposition takes place, producing Potassium Manganate (K_2MnO₄), Manganese Dioxide (MnO₂), and Oxygen gas (O₂).

• Balanced Chemical Equation:

2KMnO₄(s) → [Δ] K_2MnO₄(s) + MnO₂(s) + O₂(g)↑

Identification:**

• Gas ‘A’: Hydrogen gas (H₂)
• Oxide ‘B’: Copper(II) Oxide / Cupric Oxide (CuO)
• Chemical Equations:

1. Formation of Gas ‘A’ (Hydrogen):

Zn(s) + 2HCl(aq) → ZnCl₂(aq) + H₂(g)↑ (Gas ‘A’)

1. Reduction of Oxide ‘B’ (Copper Oxide) by Gas ‘A’:

CuO(s) (Oxide ‘B’) + H₂(g) (Gas ‘A’) → [200°C] Cu(s) + H_2O(g)

Observation & Reason:**

• Moist Blue Litmus Paper turns RED.
• Moist Red Litmus Paper remains RED (no change).
• Reason: Burning sulphur powder produces Sulphur Dioxide gas (SO₂). When SO₂ reacts with moisture on the litmus paper, it forms Sulphurous acid (H_2SO₃). Being an acidic solution, it turns blue litmus paper red.
• Chemical Equations:

1. Combustion of Sulphur

S(s) + O₂(g) → SO₂(g)

1. Reaction of SO₂ with moisture

SO₂(g) + H_2O(l) → H_2SO₃(aq) (Sulphurous acid)

(a) This is due to the extremely low density** of hydrogen gas. Hydrogen is the lightest of all known elements and is much less dense than surrounding atmospheric air, providing upward buoyant force.

• (b) This is due to the extreme combustibility (flammability) of hydrogen gas. When hydrogen reacts rapidly with oxygen in the presence of a flame, a localized miniature explosion produces a characteristic ‘pop’ sound.

Identification:**

• Compound X: Water (H_2O) (Neutral liquid, pH = 7, used for drinking).
• Gas Y: Hydrogen gas (H₂) (Evolved at cathode, volume is double, highly combustible).
• Gas Z: Oxygen gas (O₂) (Evolved at anode, half volume of Y, supports combustion).
• Chemical Equation for Electrolysis:

2H_2O(l) → [Electrolysis / Acidified] 2H₂(g)↑ (Gas Y, Cathode) + O₂(g)↑ (Gas Z, Anode)

(Mole / Volume ratio of Y : Z = 2 : 1)