Flashcards · 0620 · Topic 3

Stoichiometry flashcards

18 cards on Topic 3, subtopics 3.1 to 3.3. Pick a subtopic or study them all.

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Molecular formula: The number and type of each atom in one molecule.
State symbols: (s) solid, (l) liquid, (g) gas, (aq) aqueous — dissolved in water.
Formulae of the sulfate, nitrate, carbonate, hydroxide and ammonium ions: SO₄²⁻, NO₃⁻, CO₃²⁻, OH⁻, NH₄⁺
Empirical formulaExtended: The simplest whole-number ratio of the different atoms in a compound.
Use the ion charges to write the formula of aluminium oxide (Al³⁺, O²⁻)Extended: Al₂O₃. The lowest common multiple of 3 and 2 is 6, so 2 Al³⁺ balance 3 O²⁻.
Formula of calcium nitrate (Ca²⁺, NO₃⁻)Extended: Ca(NO₃)₂ — brackets because two nitrate ions are needed.
Ionic equation for the neutralisation of an acid by an alkaliExtended: H⁺(aq) + OH⁻(aq) → H₂O(l)

Relative atomic mass, Ar: The average mass of the isotopes of an element compared with 1/12 of the mass of an atom of carbon-12.
Relative molecular mass, Mr: The sum of the relative atomic masses of all the atoms in a molecule. (For an ionic compound: relative formula mass.)
Mr of carbon dioxide, CO₂ (Ar: C = 12, O = 16): 12 + 2 × 16 = 44
Mr of calcium carbonate, CaCO₃ (Ar: Ca = 40, C = 12, O = 16): 40 + 12 + 3 × 16 = 100

Two units for the concentration of a solution: g/dm³ and mol/dm³
The moleExtended: The amount of substance that contains 6.02 × 10²³ particles (the Avogadro constant).
Equation linking moles, mass and molar massExtended: moles = mass (g) ÷ molar mass (g/mol)
Molar gas volume at room temperature and pressure (rtp)Extended: 24 dm³ (24 000 cm³) per mole of any gas.
Equation linking moles, concentration and volumeExtended: moles = concentration (mol/dm³) × volume (dm³). Convert cm³ to dm³ by dividing by 1000.
Percentage yieldExtended: actual yield ÷ theoretical yield × 100. It can never be more than 100%.
Mass of 0.25 mol of CaCO₃ (Mr = 100)Extended: 0.25 × 100 = 25 g