Isotonicity (Part 1) - Colligative Properties and Tonicity
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Questions and Answers

What is the definition of a solution according to the text?

  • A mixture of two or more components that is homogeneous down to the molecular level (correct)
  • A mixture of two or more components that is not heterogeneous down to the molecular level
  • A mixture of two or more components that is heterogeneous down to the molecular level
  • A mixture of two or more components that is not homogeneous down to the molecular level

    • What is the component that determines the phase of the solution called?

  • Dispersed
  • Solute
  • Solvent (correct)
  • Dissolved

    • What is the effect of adding a non-volatile solute to a liquid solvent?

  • The vapor pressure of the solvent is decreased (correct)
  • The vapor pressure of the solvent is not affected
  • The vapor pressure of the solvent becomes equal to the external pressure
  • The vapor pressure of the solvent is increased

    • What is the relationship between temperature and vapor pressure of a liquid?

    <p>The higher the temperature, the higher the vapor pressure</p> Signup and view all the answers

    Which of the following is NOT considered a colligative property of a solution?

    <p>Increase in osmotic pressure</p> Signup and view all the answers

    What is the boiling point of a liquid defined as?

    <p>The temperature at which the vapor pressure of the liquid becomes equal to the external pressure of 760 mmHg</p> Signup and view all the answers

    What is the primary effect of adding a non-volatile solute to a solvent?

    <p>It decreases the vapor pressure of the solution</p> Signup and view all the answers

    How does the boiling point of a solution change when the concentration of the added solute increases?

    <p>The boiling point increases</p> Signup and view all the answers

    What is the freezing point of pure water at a pressure of 1 atm?

    <p>$0^\circ$ C</p> Signup and view all the answers

    Why is salt added to ice on roads?

    <p>To prevent the formation of ice</p> Signup and view all the answers

    What is the driving force behind osmosis?

    <p>The difference in solute concentration across the semi-permeable membrane</p> Signup and view all the answers

    What is the primary difference between boiling point elevation and freezing point depression?

    <p>Boiling point elevation occurs at higher temperatures, while freezing point depression occurs at lower temperatures</p> Signup and view all the answers

    What should pharmaceutical solutions meant for delicate membranes be adjusted to?

    <p>Same osmotic pressure as body fluids</p> Signup and view all the answers

    When RBCs are added to hypertonic solutions, what will happen?

    <p>They will shrink and become wrinkled</p> Signup and view all the answers

    Which solution causes swelling and eventual bursting (hemolysis) of RBCs when added to them?

    <p>Hypotonic solution</p> Signup and view all the answers

    What happens to RBCs when added to isotonic solutions?

    <p>They maintain their size</p> Signup and view all the answers

    What is the characteristic of isotonic solutions concerning tonicity?

    <p>Same salt concentration as RBCs</p> Signup and view all the answers

    Which method is used to measure tonicity by adjusting the osmotic pressure of a solution?

    <p>The hemolytic method</p> Signup and view all the answers

    What is the definition of osmotic pressure?

    <p>The minimum pressure required to prevent the inward flow of a solution's pure solvent through a semipermeable membrane</p> Signup and view all the answers

    What is true about the osmotic pressure of nonelectrolyte solutions of the same molal concentration?

    <p>They have identical osmotic pressures</p> Signup and view all the answers

    What happens to the osmotic pressure of an electrolyte solution compared to a nonelectrolyte solution of the same molal concentration?

    <p>The osmotic pressure is higher</p> Signup and view all the answers

    What does tonicity measure?

    <p>The osmotic pressure of two solutions separated by a semipermeable membrane</p> Signup and view all the answers

    Which solutes affect tonicity?

    <p>Only solutes that cannot cross the semipermeable membrane</p> Signup and view all the answers

    Which of the following solutions has a higher osmotic pressure than cells?

    <p>Hypertonic solutions</p> Signup and view all the answers

    What property is used to measure tonicity based on the colligative properties of a solution?

    <p>Osmotic pressure</p> Signup and view all the answers

    In the Van't Hoff equation, what does 'i' represent for electrolytes?

    <p>The number of ions into which the molecule dissociated</p> Signup and view all the answers

    What value does 'i' seem to approach for non-electrolytes in the Van't Hoff equation?

    <p>1</p> Signup and view all the answers

    Which type of solution has a low osmotic pressure or low solute concentration?

    <p>Hypotonic</p> Signup and view all the answers

    What method is used to adjust tonicity in Class II methods?

    <p>None of the above</p> Signup and view all the answers

    What property of a solution is isotonic when compared to the surrounding environment?

    <p>Low osmotic pressure</p> Signup and view all the answers

    Study Notes

    Colligative Properties of Solutions

    • A solution is a mixture of two or more components that is homogeneous down to the molecular level.
    • Solvent: the component that determines the phase of the solution and constitutes the largest proportion of the system.
    • Solute: dispersed as molecules or ions throughout the solvent; i.e. dissolved in the solvent.

    Colligative Properties

    • Depend only on the number of particles in the solution, not on their nature.
    • Include:
      • Lowering of vapor pressure
      • Depression of freezing point
      • Elevation of boiling point
      • Osmotic pressure

    Vapor Pressure

    • The vapor pressure (P0) of a liquid is the pressure at which water vapor is in thermodynamic equilibrium with its condensed state.
    • The higher the temperature, the higher the vapor pressure increases.

    Vapor Pressure Lowering

    • When a non-volatile solute is dissolved in a liquid solvent, the vapor pressure of the solvent is lowered.
    • This occurs because surface molecules of the solvent are replaced by solute molecules, which do not contribute to the vapor pressure.

    Boiling Point Elevation

    • Boiling point: the temperature at which the vapor pressure of the liquid becomes equal to an external pressure of 760 mmHg.
    • When a non-volatile solute is added to a solvent, the boiling point of the solution is higher than that of the pure solvent.
    • An increase in the concentration of the added solute is accompanied by a further decrease in the vapor pressure of the solution and a further elevation in the boiling point.

    Freezing Point Depression

    • Freezing point: the temperature at which the solid and liquid phases are in equilibrium under a pressure of 1 atm.
    • When a non-volatile solute is added to a solvent, the freezing point of the solution is lower than that of the pure solvent.
    • Example: salt is added to ice, causing it to melt at a lower temperature.

    Osmotic Pressure

    • The minimum pressure required to prevent the inward flow of a solution's pure solvent through a semi-permeable membrane.
    • Is the pressure that must be applied to the solution to prevent the passage of the solvent through a perfect semi-permeable membrane.
    • Solutions of non-electrolytes of the same molal concentration have identical osmotic pressure, but this is not true for electrolytes.

    Tonicity

    • A measure of the osmotic pressure of two solutions separated by a semi-permeable membrane.
    • Is influenced only by solutes that cannot cross the membrane, as only these exert an osmotic pressure.
    • Solutes able to freely cross the membrane do not affect tonicity because they will always be in equal concentrations on both sides of the membrane.
    • Classified into:
      • Hypertonic solutions (higher salt concentration and higher osmotic pressure than the cells)
      • Isotonic solutions (same salt concentration and same osmotic pressure as the cells)
      • Hypotonic solutions (lower salt concentration and lower osmotic pressure than the cells)

    Measurement of Tonicity

    • The hemolytic method
    • Class I methods
    • Class II methods
    • Using Van't Hoff equation

    Van't Hoff Equation

    • π = R T C for non-electrolytes
    • π = i R T C for electrolytes
    • Where R is the gas constant, T is the absolute temperature, C is the concentration in moles per liter, and i is the number of ions into which the molecule dissociates.

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    Description

    This quiz covers the concept of colligative properties in solutions, with a focus on tonicity. Topics include the definitions of solvent and solute, as well as their roles in determining the phase and composition of a solution.

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