Unit 6: Solution Chemistry

Content Outline: Net Ionic Equations & Electrolytes (6.6)

  1. Electrolytes
  1. A substance that yields (produces) ions when it dissolves and dissociates in a solvent and thus produces a solution that conducts electrical current (transferring a charge) through the solution.

For example: Hydrogen Halides (Group 17 on Periodic Table) HF, HCl, HBr, HI. You should recognize these as “acids” by your naming rules.

  1. Non-electrolytes
  1. A substance that does not yield(produce) ions when dissolved (does not dissociate) in a solvent and therefore cannot conduct electrical current.

For example: sugars, such as Sucrose (Table Sugar) in water.

  1. Strengths of electrolytes
  1. This concept of “strength” is directly proportional to the ability of a solute to form ions (percent dissociation) when dissolved.
  1. Strong Electrolytes -100% dissociation –all of the substance is dissociated in to ions Strong Conductors
  2. Weak electrolytes  <100% dissociation – not all of substance is dissociated in to ions Weak conductors
  1. Strong Electrolytes (Good Conductors of electricity…electron flow)
  1. Any compound that has close to 100% ion formation in the aqueous state. Strong Acids, Strong Bases and Soluble Salts.

For example: HCl, HBr, HI (acids), NaOH, KOH (bases) or NaCl, KCl, AgNO3 (salts)

  1. Weak Electrolytes (Poor Conductors of electricity…electron flow)
  1. Any compound that has littleion formation in the aqueous state. Weak Acids, Weak Bases, and Insoluble Salts

For example: HF (this acid has a very strong bond) or Acetic Acid. Alsosugars are weak electrolytes.

  1. Non-Electrolytes
  1. Any compound that has no dissociation and does not conduct electric current.
  1. Please do not confuse the two above terms with the terms dilute and concentrated.
  1. Strong and Weak – refer to the degree of dissociation OR ionization.
  2. Dilute and Concentrated – refer to the amount of solute dissolved in the solvent (Molarity or %Concentration)
  1. Writing Net Ionic Equations-
  1. These equations are different than chemical reaction equations.
  1. These are just focused on those Ions or compounds in the reaction that undergo a chemical change.
  1. All soluble compounds (Strong Electrolytes) are shown as being dissociated or in ion formand in the aqueous state (aq).

Hope you remember your solubility rules.

  1. If a precipitate is formed, it is shown as a solid(s).
  2. Spectator Ions
  1. These are ions found on both sides of the equation arrow and are not involved in the actual chemical reaction that is occurring.

It is like you are watching a Pro Football Game at the stadium. You are watching (spectating) the game. You are not actually involved in playing the game (reaction).

  1. Writing

Step 1: Make sure your original chemical reaction is balanced.

Step 2: Separate all soluble compounds into the component ions/molecules for reactantsproducts.

Step 3: Label any precipitates as solid (s). Know those solubility rules!

Step 4: Identify and remove any spectator ions from the equation. Theymust be the same on both sides of the equation.

Step 5: Rewrite all that remains in a new equation that only shows those items that underwent

chemical change.

These steps will be very important later in electrochemistry.

For example: CaCl2(aq) + Na2CO3(aq) CaCO3(s) + 2NaCl(aq)

Step 1: Balanced reaction…yes.

Step 2: Ca2+(aq) + 2 Cl-(aq) + 2 Na+(aq) + CO32-(aq) CaCO3(s) + 2 Na+(aq) + 2 Cl-(aq)

Step 3: CaCO3(s) is the precipitate.

Step 4: Ca2+(aq) + 2 Cl-(aq) + 2 Na+(aq) + CO32-(aq) CaCO3(s) + 2 Na+(aq) + 2 Cl-(aq) Spectator ions

Step 5: Ca2+(aq) + CO32-(aq) CaCO3(s) . This is the net ionic equation.