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Molality quiz

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  • What does ionic molality or osmolality measure in a solution?
    It measures the molality of dissolved ions within a solution.
  • How many ions does sodium chloride dissociate into when dissolved in water?
    Sodium chloride dissociates into 2 ions: sodium ion and chloride ion.
  • What is the formula for calculating osmolality?
    Osmolality is calculated by multiplying the number of dissociated ions by the molality of the compound.
  • If you have 0.30 molal sodium chloride, what is the osmolality?
    The osmolality is 0.60, since 2 ions are produced and 2 × 0.30 = 0.60.
  • Why is it important to consider the number of ions when discussing osmolality?
    Because osmolality depends on the total number of dissolved ions, not just the compound's molality.
  • What is the difference between molality and osmolality?
    Molality measures moles of solute per kilogram of solvent, while osmolality measures moles of dissolved ions per kilogram of solvent.
  • What would be the osmolality of a 0.50 molal solution of a compound that dissociates into 3 ions?
    The osmolality would be 1.50, since 3 × 0.50 = 1.50.
  • What is the osmolality of a 1.0 molal solution of a compound that does not dissociate?
    The osmolality is 1.0, since only one particle is produced per formula unit.
  • How do you determine the number of ions for osmolality calculations?
    Count the total number of ions the compound dissociates into when dissolved.
  • What is the osmolality of a 0.20 molal solution of calcium chloride (CaCl2), which dissociates into 3 ions?
    The osmolality is 0.60, since 3 × 0.20 = 0.60.
  • If a compound dissociates into 4 ions, how does this affect its osmolality compared to a compound that dissociates into 2 ions at the same molality?
    The compound that dissociates into 4 ions will have twice the osmolality of the one that dissociates into 2 ions at the same molality.
  • What units are used for osmolality?
    Osmolality is measured in osmoles per kilogram (osmol/kg) of solvent.
  • Why is sodium chloride a good example for explaining osmolality?
    Because it dissociates completely into two ions, making calculations straightforward.
  • What happens to osmolality if the molality of the solution is doubled?
    The osmolality also doubles, since it is directly proportional to molality.
  • What should you always consider when calculating osmolality for any ionic compound?
    Always consider the number of ions the compound dissociates into in solution.