Notes on Chapter 1: Chemical Reaction and Equations
A chemical reaction represents a profound transformation where reactants change into products, fundamentally altering the nature and identity of substances.
Chemical reactions can be represented through two primary notation systems:
The law of conservation of mass states that mass is neither created nor destroyed in a chemical reaction. Therefore, the number of atoms of each element must be the same on both sides of the equation. An unbalanced equation (skeletal equation) must be balanced using coefficients. For example:
Balancing involves a methodical hit-and-trial approach, carefully adjusting coefficients to equalize atomic counts.
| No. | Reaction | Equation |
|---|---|---|
| 1 | Combustion of methane | CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(g) + heat |
| 2 | Neutralization of acid and base | HCl(aq) + NaOH(aq) → NaCl(aq) + H₂O(l) + heat |
| 3 | Respiration | C₆H₁₂O₆(aq) + 6O₂(g) → 6CO₂(g) + 6H₂O(l) + energy |
| 4 | Reaction of calcium oxide with water | CaO(s) + H₂O(l) → Ca(OH)₂(aq) + heat |
| No. | Reaction | Equation |
|---|---|---|
| 1 | Photosynthesis | 6CO₂(aq) + 6H₂O(l) + energy → C₆H₁₂O₆(aq) + 6O₂(g) |
| 2 | Decomposition of calcium carbonate | CaCO₃(s) + heat → CaO(s) + CO₂(g) |
| 3 | Electrolysis of water | 2H₂O(l) + energy → 2H₂(g) + O₂(g) |
| 4 | Photodecomposition of silver chloride | 2AgCl(s) + light → 2Ag(s) + Cl₂(g) |
Procedure: Add zinc granules to dilute hydrochloric or sulfuric acid in a conical flask.
Observations:
Type: Displacement Reaction (Exothermic)
Procedure: Mix calcium oxide (quick lime) with water
Observations:
Type: Combination Reaction (Exothermic)
Procedure: Heat ferrous sulphate crystals in a boiling tube
Observations:
Type: Thermal Decomposition Reaction
Procedure: Heat lead nitrate powder in a boiling tube
Observations:
Type: Thermal Decomposition Reaction
Procedure: Electrolysis of water with dilute sulfuric acid using carbon electrodes
Observations:
Type: Electrolytic Decomposition Reaction
Procedure: Expose silver chloride to sunlight in a china dish
Observations:
Type: Photodecomposition Reaction (Used in black-and-white photography)
Procedure: Immerse iron nails in copper sulfate solution for 20 minutes
Observations:
Type: Displacement Reaction
Procedure: Mix sodium sulfate and barium chloride solutions
Observations:
Type: Double Displacement Reaction (Precipitation Reaction)
Procedure: Heat copper powder in a china dish
Observations:
Type: Oxidation Reaction
Procedure: Measure temperature changes in four different beakers with various chemical interactions