Overview
This lecture explains the concept of osmotic pressure in solutions, its everyday applications, and methods for calculating osmotic pressure, particularly for non-electrolyte and electrolyte solutions.
Osmotic Pressure: Definition and Concepts
- Osmotic pressure is the hydrostatic pressure created by the osmosis process.
- Osmosis is the movement of solvent from a hypotonic (dilute) solution to a hypertonic (concentrated) solution through a semipermeable membrane.
- In osmosis, the solvent always moves from the lower solute concentration (hypotonic) to a higher solute concentration (hypertonic).
- Applications include salted egg production, making candied fruit, IV infusions for patients, and dialysis for kidney failure.
Applications of Osmotic Pressure
- IV fluids use osmotic pressure principles to match body fluid concentrations.
- Dialysis involves transferring small molecules like urea through a semipermeable membrane by osmotic pressure.
- Reverse osmosis is used in desalination (removing salt from seawater).
Calculating Osmotic Pressure
- General formula: PV = nRT (gas law applied to solutions).
- For non-electrolyte solutions: π = MRT (where π = osmotic pressure, M = molarity, R = gas constant, T = temperature in Kelvin).
- For electrolyte solutions, account for ionization: π = iMRT (i = van 't Hoff factor).
Example Calculations
- Glucose infusion: Use π = MRT, substituting known values for glucose (a non-electrolyte) to calculate osmotic pressure.
- Isotonic NaCl solution: Find the required mass of NaCl to match blood's osmotic pressure (7.7 atm at 37°C), using the Molar Mass of NaCl and π = iMRT.
Key Terms & Definitions
- Osmotic Pressure — Pressure needed to prevent the flow of solvent through a semipermeable membrane from a dilute to a concentrated solution.
- Semipermeable Membrane — Membrane allowing only certain molecules (typically solvent) to pass through.
- Hypotonic Solution — Solution with a lower solute concentration than another solution.
- Hypertonic Solution — Solution with a higher solute concentration than another solution.
- Isotonic Solution — Solutions with equal osmotic pressure.
- Molarity (M) — Moles of solute per liter of solution.
- Gas Constant (R) — 0.082 L atm/mol K.
- Van 't Hoff Factor (i) — Number of particles a compound forms in solution.
Action Items / Next Steps
- Read about hypertonic, isotonic, and hypotonic solutions for deeper understanding.
- Complete the practice problems in your notebook and submit them after the chapter is finished.