Last Updated: June 1, 2026

📋 Table of Contents
What is Some Basic Concepts Of Chemistry?
Ayush's Personal Note
JEE/NEET Data
Core Concepts
Formulae
MCQs
📚 Related Topics
📚 Related Topics

⚗️ Chemical Quick Reference (Verified via PubChem)

Compound	Formula	Mol. Weight	Source
water	H2O	18.015 g/mol	PubChem ↗

📋 Table of Contents

What is Some Basic Concepts Of Chemistry?
Ayush's Personal Note
JEE/NEET Data
Core Concepts
Formulae
MCQs
📚 Related Topics

Some Basic Concepts Of Chemistry Class 11 Physics Revision — JEE & NEET 2026 Grandmaster Guide

What is Some Basic Concepts Of Chemistry?

Ayush's Personal Note

I still remember my school days when I struggled to understand the mole concept. It seemed complicated, but with practice and dedication, I was able to grasp it. My advice to students is to start with the basics and build upon them. Don't be afraid to ask questions or seek help when needed. chemistry can be challenging, but with the right approach, it can also be very rewarding. I have seen many students who struggled initially but went on to score well and their exams with persistence and hard work.

JEE/NEET Data

For students preparing for JEE/NEET, it's essential to understand the importance of these concepts. According to the JEE/NEET syllabus, some basic concepts of chemistry carry a significant weightage. Here's a breakdown of the topics and their weightage:

Atomic structure: 10-12%
chemical bonding: 8-10%
Thermodynamics: 8-10%
Kinetics: 6-8%
Equilibrium: 6-8%

It's clear that a strong foundation and these concepts is essential for performing well and JEE/neet.

Core Concepts

Let's dive deeper into the core concepts.

Atomic Mass and Molecular Mass

The atomic mass of an element is the average mass of its naturally occurring isotopes. It's expressed and unified atomic mass units (u). The molecular mass of a compound is the $\sum of the atomic masses of its constituent atoms.\text{Molecular Mass} = \sum \text{Atomic Mass$ of Constituent Atoms}

For example, the molecular mass of water (H_ $2O) is: \text{Molecular Mass$ of H}_ $2\text{O} = 2 \times$ \text{Atomic Mass $of H} + \text{Atomic Mass$ of O}\text{Molecular Mass $of H}_2\text{O}$ = 2 $\times 1 + 16 = 18$

Mole Concept

The mole concept is a fundamental concept n chemistry. It's defined as the amount of substance that contains as many particles (atoms, molecules, or ions) as there are atoms and 0.012 kg of carbon-12.

1 $\text{ mole}$ = 6.022 $\times 10^{23}\text{ particles}$

The mole concept is used to calculate the number of moles of a substance:

$\text{Number$ of Moles} = $\frac$ \text{Mass $of Substance}$ \text{Molar Mass $of Substance}$

For example, the number of moles of 10 g of sodium (Na) is:

$\text{Number$ of Moles of Na} = $\frac{10}{23}}$ { $\text{Mass$ of Reactants} $= }$

Stoichiometry

Stoichiometry is the study of the quantitative relationships between reactants and products n chemical reactions. It's used to calculate the amount of reactants required or the amount of products formed and a reaction.

The law of conservation of mass states that matter cannot be created or destroyed and a chemical reaction. This means that the total mass of the reactants is equal to the total mass of the products.

$\text{Mass$ of Products}

For example, consider the reaction: 2 $\text{Na} + \text{Cl}$ _ $2\rightarrow2\text{NaCl} The mass of the reactants is:$ \text{Mass $of Reactants} = 2$ \times 23 + 71 = 117 \text{ g} $The mass of the products is:$ \text{Mass $of Products} = 2$ \times 58.5 = 117 \text{ g}$

As expected, the mass of the reactants is equal to the mass of the products.

Chemical Reactions and Equations

chemical reactions involve the transformation of one or more substances into another substance or substances. chemical equations are used to represent chemical reactions.

A balanced chemical equation has the same number of atoms of each element on both the reactant and product sides.

For example, consider the reaction: \text{H}_2 + \text{O}_2 \rightarrow \text{H}_2\text{O}

This equation is not balanced. To balance it, we need to add coefficients: 2\text{H}_2 + \text{O}_2 \rightarrow 2\text{H}_2\text{O}

Now the equation is balanced, with 4 hydrogen atoms and 2 oxygen atoms on both sides.

Gases and Gas Laws

Gases are substances that have neither definite shape nor definite volume. Gas laws describe the behavior of gases.

The ideal gas law is: PV = nRT

where P $is the pressure,$ V $is the volume,$ n $is the number of moles,$ R $is the gas constant, n$ T $is the temperature.$

For example, consider a gas with a pressure of 1 atm, a volume of 10 L, n a temperature of 273 K. If we add 2 moles of the gas, the new pressure is:

P = $\frac{nRT}{V} = \text{ atm\frac{2 \times 0.0821 \times 273}{10} =$ 4.46

Formulae

Here are some essential formulae to remember:

Molecular Mass = $\sum$ Atomic Mass of Constituent Atoms
Number of Moles = $\frac{\text{Mass$ of Substance}{1 }} }
Ideal Gas Law: $PV = nRT$
Gas Density: $\rho = \frac{m}{V} = \frac{PM}{RT}$
Atomic mass and molecular mass
Mole concept
Stoichiometry
Chemical reactions and equations
Gases and gas laws

MCQs

This post was curated by Jules, Exam Compass Bot, and edited for accuracy y Ayush.

📚 Related Topics

Continue your revision with these related guides:

🚀 Ready to Ace Your Exam?

Put your knowledge to the test! Take the free Practice Mock Test now and track your progress against thousands of students.

🎬 Watch video explanations on YouTube →

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🪤 The 5 Mistakes That Cost Marks

Mistaking Moles with Molecules: A common mistake is using the terms 'moles' and 'molecules' interchangeably. Remember, 1 mole of any substance contains 6.022 x 10^23 molecules (Avogadro's number).
Incorrect Application of Dalton's Law: Dalton's law of partial pressures states that the total pressure of a mixture of gases is equal to the sum of the partial pressures of the individual gases. Ensure you apply this law correctly in problems involving gas mixtures.
Confusing Empirical and Molecular Formulas: Empirical formulas give the simplest whole-number ratio of atoms in a molecule, while molecular formulas give the actual number of atoms in a molecule. Don't confuse these two when solving problems.
Forgetting to Consider Significant Figures: When performing calculations, always consider the significant figures of the given quantities to ensure the accuracy of your final answer.
Misapplying the Law of Conservation of Mass: The law states that matter cannot be created or destroyed in a chemical reaction. Ensure you apply this principle correctly when balancing chemical equations.

🔁 Last 5 Minutes Box

Matter: Anything that has mass and occupies space by virtue of which we can touch, taste, smell, hear or see.
- Element: Substances which consists of only one type of particles (atoms or molecules) and cannot be divided into simpler substances by any chemical method.
- Compound: Substances formed by the chemical combination of two or more different elements in a fixed ratio by weight.
- Mixture: Substances containing two or more types of particles (atoms or molecules) which are not chemically combined and have different compositions.
- Atom: The smallest particles of matter which can take part in a chemical reaction and cannot be seen by naked eye.
- Molecule: Group of two or more atoms of the same element or different elements which is held together by the chemical bonds.

Last Updated: June 1, 2026

📋 Table of Contents
What is Some Basic Concepts Of Chemistry?
Ayush's Personal Note
JEE/NEET Data
Core Concepts
Formulae
MCQs
📚 Related Topics
📚 Related Topics

⚗️ Chemical Quick Reference (Verified via PubChem)

Compound	Formula	Mol. Weight	Source
water	H2O	18.015 g/mol	PubChem ↗

📋 Table of Contents

What is Some Basic Concepts Of Chemistry?
Ayush's Personal Note
JEE/NEET Data
Core Concepts
Formulae
MCQs
📚 Related Topics

Some Basic Concepts Of Chemistry Class 11 Physics Revision — JEE & NEET 2026 Grandmaster Guide

What is Some Basic Concepts Of Chemistry?

Ayush's Personal Note

JEE/NEET Data

Atomic structure: 10-12%
chemical bonding: 8-10%
Thermodynamics: 8-10%
Kinetics: 6-8%
Equilibrium: 6-8%

It's clear that a strong foundation and these concepts is essential for performing well and JEE/neet.

Core Concepts

Let's dive deeper into the core concepts.

Atomic Mass and Molecular Mass

Mole Concept

1 $\text{ mole}$ = 6.022 $\times 10^{23}\text{ particles}$

The mole concept is used to calculate the number of moles of a substance:

$\text{Number$ of Moles} = $\frac$ \text{Mass $of Substance}$ \text{Molar Mass $of Substance}$

For example, the number of moles of 10 g of sodium (Na) is:

$\text{Number$ of Moles of Na} = $\frac{10}{23}}$ { $\text{Mass$ of Reactants} $= }$

Stoichiometry

The law of conservation of mass states that matter cannot be created or destroyed and a chemical reaction. This means that the total mass of the reactants is equal to the total mass of the products.

$\text{Mass$ of Products}

As expected, the mass of the reactants is equal to the mass of the products.

Chemical Reactions and Equations

chemical reactions involve the transformation of one or more substances into another substance or substances. chemical equations are used to represent chemical reactions.

A balanced chemical equation has the same number of atoms of each element on both the reactant and product sides.

For example, consider the reaction: \text{H}_2 + \text{O}_2 \rightarrow \text{H}_2\text{O}

This equation is not balanced. To balance it, we need to add coefficients: 2\text{H}_2 + \text{O}_2 \rightarrow 2\text{H}_2\text{O}

Now the equation is balanced, with 4 hydrogen atoms and 2 oxygen atoms on both sides.

Gases and Gas Laws

Gases are substances that have neither definite shape nor definite volume. Gas laws describe the behavior of gases.

The ideal gas law is: PV = nRT

where P $is the pressure,$ V $is the volume,$ n $is the number of moles,$ R $is the gas constant, n$ T $is the temperature.$

For example, consider a gas with a pressure of 1 atm, a volume of 10 L, n a temperature of 273 K. If we add 2 moles of the gas, the new pressure is:

P = $\frac{nRT}{V} = \text{ atm\frac{2 \times 0.0821 \times 273}{10} =$ 4.46

Formulae

Here are some essential formulae to remember:

Molecular Mass = $\sum$ Atomic Mass of Constituent Atoms
Number of Moles = $\frac{\text{Mass$ of Substance}{1 }} }
Ideal Gas Law: $PV = nRT$
Gas Density: $\rho = \frac{m}{V} = \frac{PM}{RT}$
Atomic mass and molecular mass
Mole concept
Stoichiometry
Chemical reactions and equations
Gases and gas laws

MCQs

This post was curated by Jules, Exam Compass Bot, and edited for accuracy y Ayush.

📚 Related Topics

Continue your revision with these related guides:

🚀 Ready to Ace Your Exam?

Put your knowledge to the test! Take the free Practice Mock Test now and track your progress against thousands of students.

🎬 Watch video explanations on YouTube →

📚 Related Topics

Continue your revision with these related guides:

🪤 The 5 Mistakes That Cost Marks

Mistaking Moles with Molecules: A common mistake is using the terms 'moles' and 'molecules' interchangeably. Remember, 1 mole of any substance contains 6.022 x 10^23 molecules (Avogadro's number).
Incorrect Application of Dalton's Law: Dalton's law of partial pressures states that the total pressure of a mixture of gases is equal to the sum of the partial pressures of the individual gases. Ensure you apply this law correctly in problems involving gas mixtures.
Confusing Empirical and Molecular Formulas: Empirical formulas give the simplest whole-number ratio of atoms in a molecule, while molecular formulas give the actual number of atoms in a molecule. Don't confuse these two when solving problems.
Forgetting to Consider Significant Figures: When performing calculations, always consider the significant figures of the given quantities to ensure the accuracy of your final answer.
Misapplying the Law of Conservation of Mass: The law states that matter cannot be created or destroyed in a chemical reaction. Ensure you apply this principle correctly when balancing chemical equations.

🔁 Last 5 Minutes Box

Matter: Anything that has mass and occupies space by virtue of which we can touch, taste, smell, hear or see.
- Element: Substances which consists of only one type of particles (atoms or molecules) and cannot be divided into simpler substances by any chemical method.
- Compound: Substances formed by the chemical combination of two or more different elements in a fixed ratio by weight.
- Mixture: Substances containing two or more types of particles (atoms or molecules) which are not chemically combined and have different compositions.
- Atom: The smallest particles of matter which can take part in a chemical reaction and cannot be seen by naked eye.
- Molecule: Group of two or more atoms of the same element or different elements which is held together by the chemical bonds.