Test #6 Chemistry Test

Solutions and Solubility

There is usually 1 solvent, and there can be multiple solutes.

Nature of Solutes in Solutions

  • They spread evenly throughout the solution.

  • Cannot be separated by filtration

  • Can be separated by evaporation

  • Not visible; solution appears transparent.

  • May give a color to the solution

  • Do not scatter light, which means they do not interact with light, resulting in a clear and transparent solution.

Nature of Colloids

  • Colloids are heterogeneous mixtures. Due to the slightly larger particle size, colloids appear cloudy.

  • Scatter light

  • Do not separate upon standing and cannot be separated by filtration (Example: milk, whipped cream).

  • Follow the Tyndall Effect: Particles in a colloid are large enough to reflect and scatter light.

Nature of Suspensions

  • Heterogenous mixtures.

  • Due to the larger size, these particles will separate (settle out) upon standing.

  • They can be separated by filtration because the particle size is large. (Ex: Muddy water)

Water as a Solvent

  • Water is the universal solvent

    • More substances dissolve in water than in any other chemical because of its polarity.

    • They are attracted to one another better than other molecules its size. (Like dissolves like)

Solubility Curve Graph

  • Solid Solute: When temperature increases, solubility increases; Pressure has no effect on a solid/liquid.

  • Gaseous Solute: When temperature increases, solubility decreases; When pressure increases, solubility also increases.

Degree of Solubility

Unsaturated solution: more solute dissolves.

Saturated solution: no more solute dissolves.

Supersaturated solution: becomes unstable, crystals form.

Dissolution

Example: How many moles of aluminum ions and sulfate ions are produced by dissolving 1 mole of aluminum sulfate?

Answer: Al2(SO4)3 creates:

  • : 2 Al3+ ions

  • Sulfate: 3 sulfate ions

Electrolytes

  • Definition: a substance that dissolves in water to give a solution that conducts electric current. These are ionic soluble salts, acids, and bases.

    • Strong: 100% dissociation: high conductivity

    • Weak: partial dissociation, molecules and ions in solution: slight conductivity.

  • Breaks apart into ions.

Non-Electrolytes

  • Non-electrolytes: molecular substances (covalent compounds, diatomic molecules)

    • No dissociation occurs; all molecules remain in solution.

  • Breaks apart into whole molecules.

Concentration Calculation

  • Percent mass/volume:

    • %volume or mass = solute/solution * 100

      • Solution = solvent +solute

  • Concentration Calculation:

    • ppm = mass of solute/mass of solution * 10^6

Colligative Properties

  • The reduction of the freezing point of a substance is an example of a colligative property:

    • A property of a solvent that depends on the total number of solute particles present..

  • There are four colligative properties to consider

    • Vapor Pressure Lowering

      • A solvent in a closed container reaches a state of dynamic equilibrium

      • The pressure exerted by the vapor in the headspace is referred to as the vapor pressure of the solvent.

      • The addition of any nonvolatile solute to any solute in any solvent reduces the vapor pressure of the solvent.

      • Nonvolatile solutes reduce the ability

    • Freezing point depression

    • Boiling point elevation

    • Osmotic pressure