Chem 20: Chapter 5 - Notes

Water is the Universal Solvent.

• Lots of substances dissolve in water to become (aq) solutions.

Homogeneous Mixtures composed of at least one solute (what is dissolved) and one solvent (what it is dissolved in)

chemical formula: formula of solute, solvent in parenthesis.

• NH3 (aq) - dissolved in water

• L2(alc) - dissolved in alcohol

Solute Particles can be either Ionic or Molecular Compounds.

• Ionic Compounds and Polar Molecular Solutes will dissolve in Polar Solvents.

  • dissolves in water → creating an (aq) solution.

  • cannot dissolve in Non-Polar Solvents,

• Non-Polar Solutes will dissolve in Non-Polar Solvents.

  • cannot dissolve in Polar Solvents.

• Solvent Particles attract Solute Particles.

  • causes individual particles to break away from each other

• Once particles are separated and surrounded by solvents.

  • the particles become Solvated.

Temperature:

• temp ↑, rate ↑ (directly proportional)

Particle Size:

• particle size ↓ , rate ↑ (inversely proportional)

Agitation (Stirring):

• rate ↑

Nature of Solute:

• Ionic Compounds and Highly Polar Solutes dissolve faster than Slightly Polar Solutes in Polar Solvents

  • have stronger attraction → separate out faster

the ability of a substance to dissolve in a solvent (usually water).

• solubility of Ionic Compounds is determined by using the solubility table

Can be quantified by the concentration of a Saturated Solution.

• Solution is considered to be Saturated when no more solute can dissolve in a solvent at a specific temp.

• %(w/v)

• mol/L

Solubility is dependent on temperature.

• Temp Value must accompany a Solubility Value.

  • (what temp does it become soluble in?)

Every Pure Substance has a unique solubility value.

• Salt (NaCl) has a solubility value of 46g/100mL of water

  • meaning only 46g of salt can be dissolved in water.

  • if 50g salt were added, 4g would remain as a solid in the solution.

Solute is NOT REACTING with the solvent, it is only being dissolved.

• Temperature

• Pressure

• Miscibility

Solids:

• most solids - solubility ↑, temp ↑ (direct)

Liquids:

• most liquids - temp has little effect

• makes polar solutes more miscible in polar solvents

Gases:

• solubility ↓, temp ↑ (inverse)

Solids:

• little effect

Liquids:

• little effect

Gases:

• solubility ↑, pressure ↑ (direct)

Polar Liquids have higher solubility at higher temps, these liquids are known as Miscible.

• Liquids containing Small Polar Molecules with Hydrogen Bonds → dissolved completely in water, regardless of the quantity mixed.

  • ethanol will dissolve in water in any proportion with no max concentration!

• Liquids that are insoluble in each other are Immiscible.

  • difference in density → one liquid will form a layer on top of the other

  • similar densities → one will emulsify in the other

concentration of the dissolved solute is constant. (AT MAX)

• no change in observable properties

Saturated Solutions are in a Dynamic Equilibrium.

• equal amount of solute in solution crystallizing

• equal amount of solute as a solid dissolving in a solution.

Unsaturated:

• less than max amount of solute for given amount of solvent.

• can add more solute.

Saturated:

• max amount of solute for a given amount of solvent

• no more solute dissolves.

Supersaturated:

• more than max amount of solute for a given amount of solvent

• crystals (solids) may grow as more solute is added.

Substances that have water part of their crystal structure.

• can be observed by using our five senses

  • (most often what we see)

• electrolytic (conductive)

• blue litmus → red

• react with metals → produce H2(g) bubbles

• neutralized by bases

NOT SAFE IN A LAB ENVIRONMENT!

• corrosive

• sour

• electrolytic (conductive)

• red litmus → blue

• neutralized by acids

NOT SAFE IN A LAB ENVIRONMENT!

• feel slippery

• corrosive

• bitter

• ionic solute → electrolytic (conductive)

• molecular solute → non-electrolytic

• no effect on litmus

compounds that conduct electricity in an (aq) solution or in a molten (liquid) state

• able to dissociate in water → carry an electrical charge

• includes all soluble ionic, acidic and basic solutions.

aqueous solutions that do not conduct electricity

• unable to dissociate into ions → disperse

• includes most molecular compounds.

• water

• ammonia

• large portion of the solute dissociates and exists as ions

Conductivity:

• bulb burns brightly

• more bulbs lighting up

• higher # reading

Examples:

• sodium hydroxide

• sodium chloride

• hydrochloric acid

• small portion of the solute dissociates and exists as ions

Conductivity:

• bulb burns dimly

• fewer bulbs lighting up

• lower # reading

Examples:

• water

• acetic acid

• ammonia

Conductivity:

• tests (+) → 2+ lights will glow

Litmus:

• blue litmus → red

Metal Strip:

• metal will dissolve → producesH2(g) bubbles

Conductivity:

• tests (+) → 2+ lights will glow

Litmus:

• red litmus → blue

Metal Strip:

• no effect

Conductivity:

• tests (+) → 2+ lights will glow

Litmus:

• no effect

Metal Strip:

• no effect

Conductivity:

• tests (-) → 0-1 lights will glow

Litmus:

• no effect

Metal Strip:

• no effect

• neutral particles (non-electrolytes) → solutions cannot conduct electricity

  • non-electrolytes disperse electrically neutral particles throughout solution.

Disperse Formula:

• XY(s,l or g) → XY(aq)

  • change state to (aq)

• ex ) C12H22O11(s) → C12H22 O11(aq)

• when ionic compounds dissolve → ions dissociate (come apart)

  • positive ions are surrounded by negative ends of polar water molecules

    • (+) → (-) water

  • negative ions are surrounded by the positive ends of polar water molecules.

    • (-) → (+) water

Dissociate Formula:

• MX(s) → M+(aq) + X-(aq)

  • separates into charged ions, changes states

• ex ) NaCl(s) → Na+(aq) + Cl-(aq)