Unit 6: Solution Chemistry

Content Outline: Ionic Solutions (6.5)

  1. Ion
  1. An Ion is acharged particle that is the end result of an ionic or molecular (covalent bonds) compound being broken apart and an electron transfer taking place.
  2. The electron transfer creates the charges on the particles.
  3. Two types of ions exist:
  1. Anion
  1. These particles carry a negative charge. (Think angry…negative thoughts.)
  2. The negative charge is from the extra electron(s), which outnumber the protons.
  3. This particle was reduced by reduction. (“Gaining” an electron… Think “RIG”.)
  1. Cations
  1. These particles carry a positive charge. (Think cats… cats make some people happy/positive.)
  2. The positive charge is from having more protons than electrons.
  3. This particle was oxidized by oxidation. (“Loss” of electrons… Think “OIL”.)
  1. Law of Conservation of Matter
  1. Matter is neither created nor destroyed; just transferred and transformed.

In this case it is the electron(s) that was transferred between atoms and that resulted in a charge transformation of those particles.

  1. They always go together, so think “OIL RIG” for a Redox reaction.
  1. Dissociation (Sounds like “dis- associate”.)
  1. The dissolving of an Ionic compound, such as NaCl, into water causing the ionic bonds to break and release “free” ions.

For example salt in water (the water is understood by the term aqueous (aq).

NaCl  Na+(aq) + Cl-(aq)

  1. Aqueous (aq)
  1. Substance is dissolved in water.
  1. Hydration Shell
  1. These form around the “free ions” as they are separated.
  2. They form because the water is polar and attracted to the charged ions.

a. Hydrogen Bonds form as a result of the attraction.

  1. Keeps the ionic particles separated and dissolved.
  1. Not all ionic compounds dissociate into ions.
  1. Solubility Rules for Ionic Compounds: You must memorize these, as they are important!
  1. Sodium (Na), Potassium (K), and Ammonium (NH4) compounds are soluble in water.

Think “Yes on SPA in H2O”.

  1. Most Carbonates, Phosphates, and Silicates are insoluble, EXCEPT those containing Sodium (Na), Potassium (K), and Ammonium (NH4).

Think “No on CPSates, except with SPA.”

  1. Most Chlorides are soluble in hot water, EXCEPT those of Silver (Ag), Mercury I (Hg), and Lead II (Pb).

Think “Yes on Hot Water Cides, except SMiLii.” (Sounds like …“smily”.)

  1. Most Sulfides are insoluble, EXCEPT those with Calcium (Ca), Strontium (Sr), Sodium (Na), Potassium (K), and Ammonium (NH4).

Think “No on Sides, except CSSPA.”

  1. Most Sulfates are soluble, EXCEPT those with Barium (Ba), Strontium (Sr), Lead (Pb), Calcium (Ca), and Mercury (Hg).

Think “Yes on Sates, except BLSCaHG.”(Sounds like..“Blues Catalog”.)

  1. Nitrates (NO3), Acetates (CH3COOH), and Chlorates (CO3) are soluble.

Think “Yes on NACates.

  1. These rules can be useful in predicting the outcome of mixing two different solutions containing soluble compounds.
  1. If the “mixing” results in a combinations of ionsthat forms an insoluble compound, then a precipitate will form as a result of the Double Replacement Reaction.
  1. Precipitates are insoluble solids present in a solution.
  2. The precipitate occurs when the inter-molecular attractions between the ions is greater than the inter-molecular attractions between the ions and surrounding water molecules.
  1. Ionization (The “making” of ions.)
  1. Ions are “formed” from a molecular compound (covalent bonds) solute by the action of the polar solvent separating the component atoms/molecules.

Basically, “Creating ions where there were none originally.”

  1. They are Hydrated Ions, as are all ions in aqueous solutions.
  2. The energy released, as heat (exothermic), during the hydration (bonds forming between ions and water) supplies the energyto break the covalent bonds of the molecular compound (solute).
  1. The covalent bonding strength is inversely proportional to the amount of ionization that will occur.
  2. Stronger Covalent bonds = less ionization will occur.
  3. Weaker Covalent bonds = more ionization will occur.

For example, (weak covalent bonds) HCl  H+(aq) + Cl-(aq)… when in water.

(strong covalent bonds) C6H12O6 stays intact in water.

  1. Hydronium Ion (H3O+)
  1. This ion is “created” when a “free” H+ (proton) attaches to a water molecule (H2O) by a covalent bond.
  1. The H+ comes from a molecular compound containing a Hydrogen atom(s), such as an Acid like HCl.
  2. These H+ have very strong attractive forces, and so are rarely found alone in solution.
  1. The energy released (Exothermic) by “creating” the Hydronium Ion powers the breaking of the covalent bond associated with the Hydrogen atom from the molecule.