Ch-1, Chemical Reactions and Equations
Key topics within "Chemical Reactions and Equations" include understanding chemical changes, writing and balancing equations, identifying different reaction types (like combination, decomposition, displacement, and redox), and exploring concepts like stoichiometry and the law of conservation of mass.
Here's a more detailed breakdown of the key topics:
1. Chemical Reactions and Changes:
- Definition:A chemical reaction involves the rearrangement of atoms and molecules, resulting in the formation of new substances with different properties.
- Indicators of Chemical Reactions:
- Formation of a precipitate (a solid that forms from a solution).
- Evolution of a gas (formation of bubbles).
- Change in color or temperature.
- Change in mass.
- Formation of a new substance.
- Formation of a precipitate (a solid that forms from a solution).
- Physical vs. Chemical Changes:Distinguishing between changes that alter the form of a substance (physical) and those that change its composition (chemical).
2. Chemical Equations:
- Definition:A chemical equation represents a chemical reaction using symbols and formulas to show the reactants and products involved.
- Types of Chemical Equations:
- Skeletal Equations: Show the reactants and products without indicating the number of molecules involved.
- Balanced Equations: Ensure that the number of atoms of each element is the same on both sides of the equation, reflecting the law of conservation of mass.
- Skeletal Equations: Show the reactants and products without indicating the number of molecules involved.
- Writing and Balancing Equations:
- Understanding how to write balanced chemical equations by using coefficients to ensure the number of atoms of each element is the same on both sides of the equation.
- Using the law of conservation of mass to ensure that the total mass of reactants equals the total mass of products.
- Understanding how to write balanced chemical equations by using coefficients to ensure the number of atoms of each element is the same on both sides of the equation.
3. Types of Chemical Reactions:
- Combination (or Synthesis) Reactions:Two or more substances combine to form a single product.
- Example: 2H₂ + O₂ → 2H₂O
- Example: 2H₂ + O₂ → 2H₂O
- Decomposition Reactions:A single compound breaks down into two or more simpler substances.
- Example: 2H₂O₂ → 2H₂O + O₂
- Example: 2H₂O₂ → 2H₂O + O₂
- Displacement Reactions:One element replaces another in a compound.
- Example: Zn + CuSO₄ → ZnSO₄ + Cu
- Example: Zn + CuSO₄ → ZnSO₄ + Cu
- Double Displacement (or Metathesis) Reactions:Ions of two compounds exchange places, forming two new compounds.
- Example: Na₂SO₄ + BaCl₂ → BaSO₄ + 2NaCl
- Example: Na₂SO₄ + BaCl₂ → BaSO₄ + 2NaCl
- Combustion Reactions:A substance reacts rapidly with oxygen, usually producing heat and light.
- Example: CH₄ + 2O₂ → CO₂ + 2H₂O
- Example: CH₄ + 2O₂ → CO₂ + 2H₂O
- Redox Reactions (Oxidation-Reduction):Reactions involving the transfer of electrons.
- Oxidation: Loss of electrons or gain of oxygen.
- Reduction: Gain of electrons or loss of oxygen.
- Oxidation: Loss of electrons or gain of oxygen.
- Neutralization Reactions:Acid and base react to form salt and water.
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