CH 9 - Solutions

  • Definition of Solutions: Solutions are homogeneous mixtures of two or more substances.

  • Components of Solutions:
      - Solvent: Present in a larger amount.
      - Solute: Present in a smaller amount.

  • Concept of "Like Dissolves Like": Solutions form when solute and solvent have similar polarities. Examples include:   - Polar solutes like methanol dissolve in polar solvents like water.   - Non-polar solutes dissolve in non-polar solvents like oil.

  • Electrolytes:
      - Strong Electrolytes: Dissociate 100% in water, producing ions capable of conducting electric current. Examples include NaCl and KBr.   - Weak Electrolytes: Dissociate only slightly in water, resulting in solutions with few ions. Examples include acetic acid.   - Nonelectrolytes: Dissolve as whole molecules in water without forming ions. They do not conduct electricity (e.g., glucose).

  • Definition of Solubility: Maximum amount of solute that dissolves in a specified amount of solvent, influenced by temperature.

  • Saturated vs. Unsaturated Solutions:
      - Saturated Solutions: Contain the maximum amount of solute that can dissolve; undissolved solute is present.
      - Unsaturated Solutions: Contain less than the maximum amount of solute and can still dissolve more.

  • Effect of Temperature on Solubility:
      - Solids: Typically more soluble in higher temperatures.
      - Gases: Typically less soluble in higher temperatures (Henry’s Law).

  • Concentration Units:
      - Mass percent (m/m): % of mass of solute in solution.
      - Volume percent (v/v): % of volume of solute in total volume of solution.
      - Mass/volume percent (m/v): Grams of solute in 100 mL of solution.   - Molarity: Moles of solute per liter of solution (M = moles/L).

  • Dilution Equation:
      - Use the equation C1V1=C2V2C_1V_1 = C_2V_2 to calculate dilutions, where C is concentration and V is volume.

  • Properties of Solutions, Suspensions, and Colloids:
      - Solutions: Homogeneous, transparent, and do not separate.
      - Suspensions: Heterogeneous, can settle out, and can be filtered (e.g., muddy water).
      - Colloids: Intermediate particle size, cannot be filtered, but can pass through semipermeable membranes (e.g., fog).

  • Definition of Osmosis: Movement of solvent from areas of lower solute concentration to higher solute concentration through a semipermeable membrane.

  • Tonicity:
      - Isotonic Solutions: Same osmotic pressure as body fluids; ideal for cells.
      - Hypotonic Solutions: Lower solute concentration than red blood cells, causing cells to swell.
      - Hypertonic Solutions: Higher solute concentration than red blood cells, causing cells to shrink (crenation).