Some Basic Concepts of Chemistry 11 Chemistry — Revision Notes
Chemistry studies matter and its reactions. Understanding fundamental concepts like atomic mass, molar mass, and stoichiometry is essential for solving che
TL;DR: Chemistry studies matter and its reactions. Understanding fundamental concepts like atomic mass, molar mass, and stoichiometry is essential for solvin…
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Chemistry studies matter and its reactions. Understanding fundamental concepts like atomic mass, molar mass, and stoichiometry is essential for solving che
Atomic Mass Unit and Mass Number
- Atomic mass unit (amu) is 1/12th mass of carbon-12 atom
- Mass number is sum of protons and neutrons in nucleus
- Atomic number is number of protons in nucleus
- Atoms of same element with different mass numbers are isotopes
- Atomic mass is average mass of all isotopes of an element
Mole Concept
- Mole is unit of amount of substance equal to 6.022 times 10 to power 23 particles
- Avogadro's number equals 6.022 times 10 to power 23
- Molar mass is mass of one mole of substance in grams
- Number of moles equals mass divided by molar mass
- One mole of any gas at STP occupies 22.4 liters
Percentage Composition
- Percentage composition shows mass percent of each element
- Percentage of element equals (mass of element / total mass) times 100
- Used to determine empirical formula from experimental data
- Empirical formula gives simplest whole number ratio
- Molecular formula is multiple of empirical formula
Stoichiometry and Balancing Equations
- Stoichiometry relates amounts of reactants and products
- Balanced equation shows smallest whole number ratio
- Coefficient indicates number of moles in reaction
- Law of conservation of mass requires equal atoms on both sides
- Limiting reagent is consumed first; determines product amount
Molarity and Molality
- Molarity is moles of solute per liter of solution
- Molality is moles of solute per kilogram of solvent
- Molarity depends on temperature; molality does not
- Used to calculate amount of solute needed for solutions
- Dilution formula: M1V1 equals M2V2
Key Terms
- Mole: Unit of amount of substance containing 6.022 times 10 to power 23 particles
- Atomic Mass Unit: Standard unit of atomic mass equal to 1/12 mass of C-12
- Stoichiometry: Study of quantitative relationships between reactants and products
- Limiting Reagent: Reactant that is completely consumed and limits product amount
Frequently Asked Questions
Why is the molar volume of gas at STP 22.4 liters?
At standard temperature and pressure, all ideal gases follow Avogadro's law. One mole of any gas occupies 22.4 liters due to the ideal gas law and these standard conditions.
How do you identify the limiting reagent in a reaction?
Calculate the number of moles of product each reactant would produce. The reactant that produces the least amount of product is the limiting reagent.
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