amount of substance flashcards

Flashcard Set: Amount of Substance

2.2.1 Amount of Substance

  • Mole & Avogadro Constant:

    • A mole represents 6.02 × 10²³ particles.

    • Molar mass links the number of moles to the mass of a substance.

    • Formula: n=mMn = \frac{m}{M}n=Mm​, where nnn is moles, mmm is mass, and MMM is molar mass.

  • Molar Gas Volume:

    • At room temperature and pressure, 1 mole of gas occupies 24 dm³.

2.2.2 Determining Formulae

  • Empirical vs Molecular Formula:

    • Empirical formula: simplest ratio of elements.

    • Molecular formula: actual number of atoms.

  • Calculations:

    • Empirical formula uses mass or % composition.

    • Molecular formula = Molecular massEmpirical mass\frac{\text{Molecular mass}}{\text{Empirical mass}}Empirical massMolecular mass​ × empirical formula.

2.2.3 Reaction Calculations

  • Mass Calculations:

    • Use moles=massmolar mass\text{moles} = \frac{\text{mass}}{\text{molar mass}}moles=molar massmass​.

    • Stoichiometry determines reactants and products' relationships.

  • Volume Calculations:

    • Concentration=molesvolume (dm³)\text{Concentration} = \frac{\text{moles}}{\text{volume (dm³)}}Concentration=volume (dm³)moles​.

  • Gas Volumes:

    • Volume (dm³)=moles×24\text{Volume (dm³)} = \text{moles} × 24Volume (dm³)=moles×24.

2.2.4 The Ideal Gas Equation

  • Equation:

    • PV=nRTPV = nRTPV=nRT, where PPP is pressure, VVV is volume, nnn is moles, R=8.314R = 8.314R=8.314, and TTT is temperature in Kelvin.

  • Key Assumptions:

    • Gas particles have negligible volume and no intermolecular forces.

    • Limitations at high pressure or low temperature.

2.2.5 Percentage Yield & Atom Economy

  • Percentage Yield:

    • Percentage yield=actual yieldtheoretical yield×100\text{Percentage yield} = \frac{\text{actual yield}}{\text{theoretical yield}} × 100Percentage yield=theoretical yieldactual yield​×100.

  • Atom Economy:

    • Atom economy=Mass of desired productMass of all reactants×100\text{Atom economy} = \frac{\text{Mass of desired product}}{\text{Mass of all reactants}} × 100Atom economy=Mass of all reactantsMass of desired product​×100.

    • High atom economy = efficient and environmentally friendly reactions.

  • Green Chemistry:

    • Optimizing atom economy reduces waste and improves sustainability.