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Questions and Answers
What is the primary factor that drives the movement of solvent molecules across a semi-permeable membrane?
What is the primary factor that drives the movement of solvent molecules across a semi-permeable membrane?
- The temperature of the solvent molecules
- The osmotic pressure exerted by the solute
- The vapour pressure differential across the membrane (correct)
- The concentration of solute on both sides of the membrane
Which of the following correctly defines osmotic pressure?
Which of the following correctly defines osmotic pressure?
- The pressure applied to maintain a specific concentration of solute
- The pressure needed to make fluid levels equal on both sides of a membrane (correct)
- The pressure measured when a solution is at equilibrium
- The pressure needed to increase the solute concentration in the solution
What is the difference between osmolality and tonicity?
What is the difference between osmolality and tonicity?
- Osmolality depends on the solvent, while tonicity depends on the solute concentration
- Osmolality is measured in kg of solvent, while tonicity is measured in liters of solution
- Osmolality measures total solute, while tonicity measures active solute particles only
- Osmolality is specific to a solution, whereas tonicity references a particular membrane (correct)
What is meant by the term 'colligative property'?
What is meant by the term 'colligative property'?
Which of the following statements about osmolarity is correct?
Which of the following statements about osmolarity is correct?
What is the primary difference between tonicity and osmolarity?
What is the primary difference between tonicity and osmolarity?
Which method uses the freezing point of solutions to estimate osmotic pressure?
Which method uses the freezing point of solutions to estimate osmotic pressure?
When calculating tonicity, what substance can be added to adjust to plasma levels?
When calculating tonicity, what substance can be added to adjust to plasma levels?
In the concentration method of tonicity calculations, what do you subtract from the standard osmolarity?
In the concentration method of tonicity calculations, what do you subtract from the standard osmolarity?
What is the freezing point of a 0.9% w/v NaCl aqueous solution?
What is the freezing point of a 0.9% w/v NaCl aqueous solution?
What does the sodium chloride equivalent method determine?
What does the sodium chloride equivalent method determine?
What is tonicity unable to provide in terms of measurement?
What is tonicity unable to provide in terms of measurement?
What unit is osmolarity typically expressed in?
What unit is osmolarity typically expressed in?
Flashcards
Tonicity
Tonicity
The tendency of a solution to draw water across a semi-permeable membrane, relative to another solution.
Osmolality
Osmolality
The concentration of osmotically active substances in a solution.
Osmosis
Osmosis
The movement of solvent molecules across a semi-permeable membrane from a region of high solvent concentration to a region of low solvent concentration.
Osmotic Pressure
Osmotic Pressure
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Isotonic Adjustment
Isotonic Adjustment
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Concentration Method
Concentration Method
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Freezing Point Depression (FPD) Method
Freezing Point Depression (FPD) Method
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Sodium Chloride Equivalent Method
Sodium Chloride Equivalent Method
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NaCl Equivalent
NaCl Equivalent
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Study Notes
Parenteral Tonicity
- Osmosis: Movement of solvent molecules across a semi-permeable membrane, from a high solvent concentration (low solute) to a low solvent concentration (high solute).
- Open system: Adding solute lowers the vapor pressure on one side, causing solvent to move across the membrane, balancing vapor pressure and raising the solution side liquid level.
- Osmotic pressure: The pressure needed to prevent solvent movement across a semi-permeable membrane. This pressure is the same on both sides of the membrane in equilibrium.
- Colligative properties: Properties of solutions arising from solute particles disrupting solvent properties. These disruptions are directly influenced by the concentration of the solute, but not its identity
Colligative Properties
- Lowering of Vapor Pressure: The addition of solute reduces the solvent's vapor pressure.
- Boiling Point Elevation: Addition of solute increases the solvent's boiling point, due to the required increase in energy to overcome the reduced vapor pressure.
- Freezing Point Depression: Addition of solute lowers the solvent's freezing point.
Osmolarity & Osmolality
- Osmolarity: The number of osmotically active substances per liter of solution.
- Osmolality: The number of osmotically active substances per kilogram of solvent.
- 1 Osmol: Represents the number of osmotically active substances associated with 1 mole.
- Avogadro's number: 6.022 x 1023 molecules/mole
Osmolarity/Osmolality values
- 1 Osmolar aqueous solution: Exerts an osmotic pressure of 22.4 atm at 0°C. Freezes at -1.86°C, and boils at 100.52°C
Tonicity
- Tonicity: Measure of osmotic pressure gradient across a membrane, considering solutes that do not cross the membrane.
- Isotonic: Solution that doesn't alter cell volume. The osmotic pressure is the same inside and outside of the cell.
- Hypotonic: Lower osmotic pressure than the cell contents. Water moves into the cell, causing it to swell and potentially burst.
- Hypertonic: Higher osmotic pressure than the cell contents: Water moves out of the cell, causing it to shrink.
Methods for Calculating Tonicity
- Concentration Method: Assumes additive effects of all components in calculating the total osmolarity and adjusts accordingly to match a desired tonicity value for a formulation
- Freezing Point Depression Method (FPD): Uses freezing point depression as a surrogate for osmotic pressure and additive effects.
- Sodium Chloride Equivalent Method (SCE): Determines the amount of sodium chloride necessary to match the osmotic pressure of a given solution to ensure isotonicity.
Adjustment of Tonicity - SCE Method
- Calculate: Total NaCl equivalent of all drug components.
- Subtract: Calculated value from 0.9% standard value to determine the required NaCl adjustment.
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Description
Explore the concepts of parenteral tonicity and colligative properties, including osmosis, osmotic pressure, and the effects of solute on vapor pressure and boiling point. This quiz will test your understanding of how solute concentration influences solvent characteristics. Challenge your knowledge of these essential chemistry principles!
