Carbon and its Compounds

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Home Concept Boosters CBSE CBSE Class 10 Science Carbon and its Compounds

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How to Use This Page

Read each concept carefully, then check the formula, common mistake, and exam tip before moving to the next. This page completely covers Carbon and its Compounds for CBSE Class 10 Science, introducing you to the vast and fascinating world of Organic Chemistry.

Key Concepts

Class 10 · Science · Chemistry

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The element of life and infinite combinations

Class 10 · Ch 4

Covalent Bonding Definition

Carbon has 4 valence electrons. It cannot easily gain 4 (too much repulsion) or lose 4 (requires too much energy). Instead, it shares electrons with other atoms to form strong Covalent Bonds.

$$\text{Bonding entirely by Sharing of Electron Pairs}$$

Versatile Nature of Carbon Concept

Millions of carbon compounds exist due to two unique properties:
Catenation: The ability of carbon to form long chains, branches, and rings with other carbon atoms.
Tetravalency: Having a valency of 4, it can bond with 4 other atoms simultaneously.

Allotropes of Carbon Examples

Different physical forms of the same element.
Diamond: 3D rigid structure, hardest substance, insulator.
Graphite: Hexagonal layers that slide, soft/lubricating, excellent conductor of electricity.
Fullerene (C-60): Football-shaped spherical molecule.

Hydrocarbons Formulas

Compounds made only of Carbon and Hydrogen.
Alkanes (Saturated): Single bonds only. General formula $\mathrm{C_nH_{2n+2}}$.
Alkenes (Unsaturated): At least one double bond. Formula $\mathrm{C_nH_{2n}}$.
Alkynes (Unsaturated): At least one triple bond. Formula $\mathrm{C_nH_{2n-2}}$.

Homologous Series Formula

A family of organic compounds having the same functional group and similar chemical properties. Successive members differ strictly by a $\mathrm{-CH_2}$ unit and a mass of 14 u.

$$\mathrm{CH_4 \xrightarrow{+CH_2} C_2H_6 \xrightarrow{+CH_2} C_3H_8 \dots}$$

Functional Groups Symbols

Heteroatoms (like O, Cl, N) that replace hydrogen in the chain and dictate the chemical properties of the compound.
Alcohol: $\mathrm{-OH}$ (Suffix: -ol)
Aldehyde: $\mathrm{-CHO}$ (Suffix: -al)
Ketone: $\mathrm{>C=O}$ (Suffix: -one)
Carboxylic Acid: $\mathrm{-COOH}$ (Suffix: -oic acid)

Chemical Properties of Carbon Reactions

Combustion: Burns in oxygen to give $\mathrm{CO_2}$, $\mathrm{H_2O}$, heat, and light.
Addition: Unsaturated hydrocarbons add hydrogen (Hydrogenation) in the presence of Ni/Pd catalysts to become saturated.
Substitution: In presence of sunlight, Chlorine replaces Hydrogen in alkanes.

Ethanol & Ethanoic Acid Properties

Ethanol ($\mathrm{C_2H_5OH}$): Good solvent, active ingredient in alcoholic drinks. Reacts with Na to give $\mathrm{H_2}$ gas.
Ethanoic Acid ($\mathrm{CH_3COOH}$): Also called acetic acid (vinegar). Weak acid, reacts with carbonates to give $\mathrm{CO_2}$ gas.

Esterification Formula

The reaction between an alcohol and a carboxylic acid in the presence of concentrated $\mathrm{H_2SO_4}$ to form a sweet-smelling substance called an Ester. Used in perfumes and flavorings.

$$\mathrm{CH_3COOH + C_2H_5OH \xrightarrow{H_2SO_4} CH_3COOC_2H_5 + H_2O}$$

Soaps and Micelles Concept

Soaps are sodium/potassium salts of long-chain fatty acids. They have a Hydrophilic (water-loving) ionic head and a Hydrophobic (water-fearing) carbon tail. In water, they cluster into spherical structures called Micelles to trap oil and dirt.

Concept Deep Dive

Why Graphite Conducts but Diamond Doesn’t

A tale of valence electrons

Core Concept

Both Diamond and Graphite are made of exactly 100% pure carbon. So why the difference?

In Diamond, each carbon atom is bonded to 4 other carbon atoms. All 4 of its valence electrons are locked up in tight covalent bonds. There are zero free electrons, making it a perfect insulator.

In Graphite, each carbon atom is bonded to only 3 other carbon atoms in flat, hexagonal sheets. This leaves exactly one free, delocalized electron per carbon atom. These free electrons can move through the sheets, allowing graphite to conduct electricity exceptionally well!

The Cleaning Action of Soap

How Micelles trap dirt

Everyday Chemistry

Dirt is mostly oily, and as we know, oil and water don’t mix. Water alone cannot wash away oil.

When soap is added, the hydrophobic tail (carbon chain) attaches itself to the oily dirt, because it hates water. The hydrophilic head (ionic part) faces outward, bonding with the surrounding water. These soap molecules surround the oil droplet entirely, creating a microscopic sphere called a Micelle.

Because the outside of the micelle is covered in negative charges, the micelles repel each other and stay suspended in the water as an emulsion. When you rinse with water, the whole micelle (carrying the dirt inside) washes away!

Compare & Contrast

✗ Soaps

Sodium or Potassium salts of long-chain carboxylic acids.
Biodegradable and environmentally friendly.
Fail in Hard Water: React with Calcium and Magnesium ions in hard water to form an insoluble white solid called scum, wasting the soap.

✓ Detergents

Sodium salts of long-chain sulphonic acids or ammonium salts.
Often non-biodegradable (can cause water pollution).
Work in Hard Water: Their calcium/magnesium salts are soluble in water, so they do NOT form scum and lather easily even in hard water.

Common Mistakes to Avoid

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Mistake 1

Miscounting Carbons in Functional Groups: When naming compounds with groups like Aldehydes ($\mathrm{-CHO}$) or Carboxylic Acids ($\mathrm{-COOH}$), students often forget to count the carbon inside the functional group. For example, $\mathrm{CH_3COOH}$ has TWO carbons in total, so its root name is “ethan-“, making it Ethanoic acid, not Methanoic acid.

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Mistake 2

Confusing -al and -ol: Be extremely careful with spelling!
Propanol ($\mathrm{CH_3-CH_2-CH_2OH}$) is an Alcohol.
Propanal ($\mathrm{CH_3-CH_2-CHO}$) is an Aldehyde.
Writing an ‘a’ instead of an ‘o’ changes the entire chemical family and will cost you marks.

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Mistake 3

First member of Ketones: The functional group of a ketone ($\mathrm{>C=O}$) must be attached to two other carbon atoms (it must be in the middle of a chain). Therefore, a ketone cannot have 1 or 2 carbons. The simplest possible ketone is Propanone (Acetone), which has 3 carbons.

Exam Tips

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Tip 1

The “X and Y” Mystery Questions: Examiners love asking identifying questions like: “Compound X reacts with sodium to give hydrogen gas. X reacts with Y in presence of acid to give a sweet-smelling substance Z.”
Cheat Sheet:
– X = Ethanol (Alcohol reacts with Na).
– Y = Ethanoic Acid.
– Z = Ester (sweet smelling).

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Tip 2

Drawing Electron Dot Structures: When drawing molecules like $\mathrm{CO_2}$ or $\mathrm{N_2}$, remember that oxygen forms a double bond (sharing 2 pairs / 4 electrons) and nitrogen forms a triple bond (sharing 3 pairs / 6 electrons). Always draw the circles so that every atom has exactly 8 electrons in its shell (except Hydrogen, which needs 2).

Expected Exam Questions

Board Pattern Questions

Class 10 · Science · CBSE Exam

Class 10 · Chemistry

Why are carbon and its compounds used as fuels for most applications? Write the chemical equation for the combustion of methane. [2 marks]

Answer High calorific value, clean combustion. 📝

Explanation

Carbon and its compounds (hydrocarbons) undergo highly exothermic combustion reactions. They release a tremendous amount of heat and light energy when burned in air. Furthermore, saturated hydrocarbons burn with a clean flame without leaving much residue (soot), making them excellent, efficient fuels.
Equation: $\mathrm{CH_{4(g)} + 2O_{2(g)} \rightarrow CO_{2(g)} + 2H_2O_{(g)} + Heat + Light}$

What is a homologous series? State any two characteristics of a homologous series. [3 marks]

Answer A series of compounds with same functional group, differing by $\mathrm{-CH_2}$. 📝

Explanation

A homologous series is a family of organic compounds having the same general formula, the same functional group, and similar chemical properties.
Characteristics:
1. Any two consecutive members differ in their formula by a $\mathrm{-CH_2}$ unit, and in their molecular mass by $14 \text{ u}$.
2. All members show similar chemical properties (because they have the same functional group).
3. They show a gradual change (gradation) in their physical properties (like melting/boiling points) as molecular mass increases.

How is vegetable ghee manufactured from vegetable oil? What is the role of the catalyst in this reaction? [2 marks]

Answer By Hydrogenation (Addition reaction) using Nickel/Palladium catalyst. 📝

Explanation

Vegetable oils contain unsaturated carbon chains (double bonds). When hydrogen gas is passed through vegetable oils in the presence of a catalyst like Nickel ($\mathrm{Ni}$) or Palladium ($\mathrm{Pd}$), an Addition Reaction occurs. The double bonds break, hydrogen atoms are added, and the oil converts into saturated solid fats (vegetable ghee). This process is called Hydrogenation.
The role of the catalyst (Ni/Pd) is to provide a surface for the reaction to occur and to speed up the reaction without being consumed.

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