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Lesson
Some Basic Concepts of Chemistry — Complete Lesson
Foundations of Chemistry
Laws of Chemical Combination
- Law of Conservation of Mass (Lavoisier) — Mass is neither created nor destroyed in a chemical reaction
- Law of Definite Proportions (Proust) — A compound always has the same elements in the same ratio by mass
- Law of Multiple Proportions (Dalton) — When two elements form multiple compounds, ratios are in simple whole numbers
The Mole Concept
1 mole = 6.022 × 10²³ particles (Avogadro's Number)
Molar mass = mass of 1 mole of substance (in grams)
Number of moles = Given mass / Molar mass
Stoichiometry
Stoichiometry uses balanced equations to calculate quantities in reactions:
2H2 + O2 ? 2H2O
2 mol hydrogen + 1 mol oxygen ? 2 mol water
2 mol hydrogen + 1 mol oxygen ? 2 mol water
Important Formulas
| Quantity | Formula |
|---|---|
| Molarity (M) | Moles of solute / Volume of solution (L) |
| Empirical formula | Simplest whole-number ratio of atoms |
| Molecular formula | n × Empirical formula (n = Molar mass / EF mass) |
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MCQ Practice
Some Basic Concepts of Chemistry — MCQ Practice
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