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Concentration Units: Flashcards

Revise molarity, molality, mass percent, ppm and mole fraction, and converting between them.

10 cardsIntermediate

10 cards

  1. Question
    Define molarity.
    Answer

    Moles of solute per litre of solution (mol/L).

  2. Question
    Define molality.
    Answer

    Moles of solute per kilogram of solvent (mol/kg).

  3. Question
    Define mass percent.
    Answer

    (mass of solute ÷ mass of solution) × 100 %

  4. Question
    What is 1 ppm, and what is it roughly equal to in dilute water solutions?
    Answer

    1 g of solute per 10⁶ g of solution; about 1 mg/L.

  5. Question
    Define mole fraction.
    Answer

    Moles of one component ÷ total moles of all components. No unit; all fractions add to 1.

  6. Question
    Which concentration units do not change with temperature?
    Answer

    Molality, mass percent, ppm and mole fraction (they use masses, not volumes).

  7. Question
    What extra information do you need to convert molarity into molality?
    Answer

    The density of the solution.

  8. Question
    5.00 g NaCl in 95.0 g water: what is the mass percent?
    Answer

    5.00 g ÷ 100.0 g × 100 % = 5.00 %

  9. Question
    Why are molarity and molality almost equal for dilute aqueous solutions?
    Answer

    1 L of a dilute solution contains almost exactly 1 kg of water.

  10. Question
    Which concentration unit is used for colligative properties?
    Answer

    Molality (mol/kg).