Solutions and Solutes Flashcards

Solubility Basics

Solutions

• A solution is a homogeneous mixture consisting of a solute and a solvent.

• Solute: The substance that gets dissolved. A solution can contain more than one solute.

• Solvent: The substance that does the dissolving, typically present in a greater amount.

Miscibility and Solubility

• Immiscible: Substances that do not mix together.

• Suspension: A heterogeneous mixture where layers form (e.g., oil and vinegar, sand and water).

• Heterogeneous: Different throughout.

• Colloid: Appears homogeneous but is heterogeneous upon closer inspection (e.g., milk).

• Soluble/Miscible: Substances that mix together to become homogeneous (e.g., salt and water, sugar and water).

• "Like dissolves like": Molecules with similar intermolecular forces tend to dissolve in each other.

Factors Affecting Solubility

• Molecular Properties:

  • Many, but not all, ionic substances will dissolve in water due to attraction to water molecules.

  • Many nonpolar and covalent compounds do not dissolve in water.

  • Nonpolar substances are more attracted to each other than to water. Water is more attracted to itself than to nonpolar substances.

• Temperature:

  • As temperature increases, solubility generally increases.

  • Higher temperatures cause solvent molecules to move faster, speeding up the dissolving of the solute (e.g., hot water vs. cold water).

• Particle Size:

  • As particle size decreases, solubility increases.

  • Larger particles require more collisions from the solvent to dissolve (e.g., fine salt vs. chunky salt).

• Mixing/Shaking:

  • Increased shaking/mixing increases solubility.

  • Increased movement leads to more collisions between solute and solvent (e.g., protein shakes).

Solution Concentration

• Solution concentration refers to the amount of solute dissolved in a specific amount of solution.

• It depends on the quantity of solute and the quantity of solvent.

Parts Per Million (PPM)

• One way to measure concentration.

• ppm or mg/L.

• Measurement of the mass of a chemical or contaminant per unit.

• Formula: $PPM = \frac{\text{grams of solute}}{\text{grams of solution}} \times 1,000,000$$$PPM = \frac{\text{grams of solute}}{\text{grams of solution}} \times 1,000,000$$

Molarity

• Another way to measure concentration; defined as moles per liter.

• Units: mol/L or M.

• Higher concentration: add more solute.

• Lower concentration: add more solvent.

• Formula: $\text{Molarity} = \frac{\text{moles of solute}}{\text{liters of solution}}$$$\text{Molarity} = \frac{\text{moles of solute}}{\text{liters of solution}}$$

Relationships

• As the solute increases, the solution volume doesn't change, but the molarity increases.

• As the solute decreases, the solution volume doesn't change, but the molarity decreases.

• If the solute doesn't change, and the solution volume decreases, the molarity increases.

• The solute and molarity have a direct relationship, while the solution volume and molarity have an inverse relationship.