Grade 10
  1. Matter and its properties  1.1. States of matter  1.2. Physical and chemical properties of matter  1.3. Classification of substances (elements, compounds, mixtures)  1.4. Changes in Matter (Physical and Chemical Changes)  1.5. Law of conservation of mass and law of definite proportions
  2. Atomic Structure  2.1. Historical development of the atomic model  2.2. Subatomic particles (protons, neutrons, electrons)  2.3. Atomic number, mass number and isotopes  2.4. Electronic Configuration and Energy Levels  2.5. Valency, ion formation and oxidation state
  3. Periodic table  3.1. History and Development of the Periodic Table  3.2. Modern Periodic Law and Periodic Trends  3.3. Groups and Periods in the Periodic Table  3.4. Trends in the Periodic Table  3.5. Metals, non-metals, metalloids and their properties  3.6. Noble gases and their chemical inertness
  4. Chemical bond  4.1. Formation of Chemical Bonds (Octet Rule)  4.2. Ionic Bonding and Properties of Ionic Compounds  4.3. Covalent Bond and Properties of Covalent Compounds  4.4. Metallic bond and its properties  4.5. Molecular geometry and VSEPR theory  4.6. Polarity and dipole moment of molecules  4.7. Intermolecular forces
  5. Chemical Reactions and Equations  5.1. Types of Chemical Reactions  5.2. Writing and balancing chemical equations  5.3. Law of conservation of mass in chemical reactions  5.4. Factors Affecting Chemical Reactions  5.5. Catalysts and their role in chemical reactions  5.6. Exothermic and Endothermic Reactions
  6. Stoichiometry and Chemical Calculations  6.1. Mole concept and Avogadro number  6.2. Molar Mass and Gram-Mole Conversions  6.3. Empirical and molecular formula  6.4. Stoichiometric calculations and chemical yield  6.5. Limiting and Excess Reactants
  7. Acids, Bases and Salts  7.1. Properties and Definitions of Acids and Bases (Arrhenius, Bronsted-Lowry, Lewis)  7.2. pH Scale, pOH, and Indicators  7.3. Neutralization reactions and salt formation  7.4. Strength of Acids and Bases (Strong vs. Weak Acids and Bases)  7.5. Common Acids and Bases in Daily Life  7.6. Salts, their solubility and applications
  8. Metals and Nonmetals  8.1. Physical and chemical properties of metals  8.2. Physical and Chemical Properties of Non-Metals  8.3. Reactivity Series of Metals and Displacement Reactions  8.4. Extraction of metals from ores  8.5. Corrosion, its causes and prevention  8.6. Alloys, their composition and uses
  9. Carbon and its compounds  9.1. Allotropes of Carbon  9.2. Hydrocarbons and their classification (alkanes, alkenes, alkynes)  9.3. Functional groups in organic compounds  9.4. Nomenclature of organic compounds (IUPAC system)  9.5. Isomerism in organic chemistry (structural and geometrical)  9.6. Important organic reactions (combustion, addition, substitution, polymerization)  9.7. Applications of organic compounds in industry and daily life
  10. Environmental Chemistry  10.1. Air Pollution (Sources, Effects and Control)  10.2. Water Pollution (Causes, Effects and Remedies)  10.3. Greenhouse effect and global warming  10.4. Ozone layer depletion and its effects  10.5. Green Chemistry and Its Applications  10.6. sustainable chemistry practice
  11. Thermochemistry  11.1. Heat and Energy Changes in Chemical Reactions  11.2. Exothermic and Endothermic Reactions  11.3. Enthalpy, enthalpy change, and heat of reaction  11.4. Specific heat capacity and calorimetry  11.5. Energy Changes in Combustion Reactions
  12. Electrochemistry  12.1. Electrolytes and non-electrolytes  12.2. Electrolysis and its applications (electroplating, extraction of metals)  12.3. Redox reactions (oxidation and reduction)  12.4. Galvanic cell and electrochemical series  12.5. Corrosion and electrochemical prevention methods
  13. Chemical kinetics and equilibrium  13.1. Rate of chemical reactions and its measurement  13.2. Factors affecting the reaction rate (catalyst, temperature, concentration)  13.3. Reversible and irreversible reactions  13.4. Dynamic equilibrium and equilibrium constant  13.5. Le Chatelier's principle and its applications
  14. Gases and Gas Laws  14.1. Properties of gases and kinetic molecular theory  14.2. Boyle's Law (Pressure-Volume Relation)  14.3. Charles's Law  14.4. Gay-Lussac's Law  14.5. Combined Gas Law and Ideal Gas Law  14.6. Real Gases vs Ideal Gases
  15. Nuclear Chemistry  15.1. Introduction to Radioactivity and Nuclear Reactions  15.2. Types of radioactive decay (alpha, beta, gamma)  15.3. Half-life and applications of radioactive isotopes  15.4. Nuclear fission and fusion reactions  15.5. Nuclear power generation and its environmental impact

Grade 10 → Chemical Reactions and Equations ↓


Writing and balancing chemical equations


Writing and balancing chemical equations is an essential skill in chemistry. It is the way chemists communicate about chemical reactions, helping them understand how substances change during chemical changes. In this guide, we will explore what chemical equations are, how to write them, and how to make sure they are balanced. This process ensures that the law of conservation of mass holds, which states that mass cannot be created or destroyed in a chemical reaction.

What is the chemical equation?

A chemical equation is a symbolic representation of a chemical reaction. It shows the substances involved in the reaction: the reactants are the substances that undergo change, and the products are the substances that are formed. The general form of a chemical equation is:

reactants → products

The arrow in a chemical equation can be read as "yields" or "produces." For example, when hydrogen and oxygen react to form water, the chemical equation would look like this:

2H 2 + O 2 → 2H 2 O

This equation tells us that two molecules of hydrogen gas (H 2) react with one molecule of oxygen gas (O 2) to form two molecules of water (H 2 O).

Parts of a chemical equation

A chemical equation consists of several parts:

  • Reactants: These are the starting materials in a chemical reaction. They are written on the left-hand side of the equation.
  • Products: These are the substances that are formed as a result of a chemical reaction. They are written on the right side of the equation.
  • Chemical symbol: Each element is represented by a chemical symbol (for example, H for hydrogen, O for oxygen).
  • Coefficients: Numbers placed in front of chemical formulas to balance the equation. They indicate the number of units of each substance involved in the reaction.
  • Arrows: Separates reactants from products and shows the direction of the reaction.

Steps for writing and balancing a chemical equation

Follow these steps to write and balance a chemical equation:

Step 1: Identify the reactants and products

The first step is to identify the reactants and products of the chemical reaction. This information is often provided in a word problem or description. For example:

Sodium reacts with chlorine gas to form sodium chloride.

Step 2: Write the unbalanced equation

Next, write the chemical formulas of all the reactants and products. Place the reactants on the left and the products on the right of the arrow.

2 Na + Cl 2 → NaCl

Step 3: Balance the equation

The equation must be balanced so that the same number of each type of atom appears on both sides of the equation. To achieve this, adjust the coefficients.

Let's take our unbalanced equation:

2 Na + Cl 2 → NaCl

Sodium (Na) and chlorine (Cl) are not balanced: on the left there is 1 Na and 2 Cl atoms, and on the right, the sodium chloride molecule has 1 Na and 1 Cl atom. Balance the chlorine by placing a coefficient of 2 in front of NaCl:

2Na + Cl 2 → 2NaCl

Now, balance the sodium by placing a coefficient of 2 in front of Na:

2Na + Cl2 → 2NaCl2

This balanced equation shows that two sodium atoms react with one chlorine molecule to form two units of sodium chloride.

Visual example

Let's imagine a simple chemical reaction. Consider the decomposition of hydrogen peroxide:

2H 2 O 2 → 2H 2 O + O 2
H 2 O 2 H 2 O 2 H2O H2O O2

Tips for balancing chemical equations

  • Start with individual elements: Balance elements that appear in only one reactant and one product first. Leave elements that exist in multiple compounds or molecules for later steps.
  • Balance polyatomic ions as single units: If a polyatomic ion appears unchanged on either side of the equation, you can balance it as a whole rather than balancing each element separately.
  • Save hydrogen and oxygen for last: these are often found in many compounds on both sides, so balance them once the other elements are stabilized.
  • Check your work: Count the number of each type of atom on both sides to make sure they match. Adjust the coefficients as needed to achieve balance.

Importance of balancing chemical equations

Balancing chemical equations is important because it reflects the law of conservation of mass. This law states that mass cannot be created or destroyed in a chemical reaction. Balancing equations ensures that the same amount of atoms and mass are present before and after the reaction, indicating that no atoms have been lost or gained. Accurate chemical equations help chemists understand, predict, and control reactions in laboratory and industrial settings.

Practice problems

Try balancing these equations:

  1. CH 4 + O 2 → CO 2 + H 2 O
  2. Fe + O 2 → Fe 2 O 3
  3. N 2 + H 2 → NH 3

Balancing these equations will improve your ability to write and balance chemical equations. Remember, practice is key to mastering this skill.

Conclusion

Writing and balancing chemical equations is a fundamental skill in the study of chemistry. By accurately representing the substances involved and ensuring that mass is conserved, chemists can effectively communicate and understand chemical processes. As with any skill, practice is key, and by working through the examples and following the steps outlined, you will become proficient at writing and balancing chemical equations.


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Types of Chemical Reactions
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Writing and balancing chemical equations

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