Chemical Quantities and Reactions - Summary

Chapter 7: Chemical Quantities and Reactions

• Mole Concept:

  • 1 mole = $6.022 \times 10^{23}$ items (Avogadro's number).

  • Items can be atoms, molecules, etc.

• Molar Mass:

  • Mass of one mole of substance.

  • Molecular weight: Mass of one mole of specific molecule.

  • Formula weight: Mass of one mole of ionic compound.

  • Units: grams per mole (g/mol).

• Molar Mass Examples:

  • Ethanol (C2H6O): 46.0688 g/mol.

  • Sodium Chloride (NaCl): 58.44277 g/mol.

  • Gasoline: ~114 g/mol (varies due to composition).

• Stoichiometry:

  • Mole calculations based on balanced equations.

  • E.g., calculating molar mass of FeSO4:

  • Fe: 55.85 g, S: 32.07 g, O: 16 g

  • Molar mass = 151.92 g/mol.

• Balanced Chemical Equations:

  • Must have equal moles of each element on both sides.

  • Stoichiometric coefficients indicate the ratio of reactants to products.

• Types of Reactions:

  • Combination: Two substances combine (e.g., $H<em>2 + Br</em>2 \to 2HBr$).

  • Decomposition: Single substance breaks into products (e.g., $2H<em>2O \to 2H</em>2 + O_2$).

  • Single Replacement: One element replaces another in a compound.

  • Double Replacement: Exchange of ions between two compounds.

  • Combustion: Hydrocarbon reacts with O2 to produce CO2 and H2O.

• Example Calculation:

  • Ammonia production: $N<em>2 + 3H</em>2 \to 2NH_3$

  • If 1.4 moles of H2 react, produce 0.93 moles of NH3.

• Dimensional Analysis:

  • Convert grams to moles and vice versa using molar mass.

  • Example: 3.64 g of H2 produces 20.5 g of NH3.

• Key Takeaways:

  • Understand moles, molar mass, and balancing reactions for successful stoichiometric calculations.

  • Use balanced equations to determine mass and number of moles in reactions.