ACIDS AND BASES

 Define electrolyte and explain the association with weak and strong.  Explain the difference between weak and strong acid and base.  Explain and compare dilute and concentrated solutions of acid or base.

HA + H 2 O base acid H 3 O + + A - Con. baseCon. acid B + H 2 O base acid BH + + OH - Con. base Con. acid

For a solution to conduct an electric current, charged particles or ions must be present in the solution.

Electrolytes - conduct an electric current when in aqueous solution or when in a molten state. All ionic compounds act as electrolytes (as do highly polar molecular compounds). Most molecular compounds are non-electrolytes. NaCl (s) Na + (aq) + Cl – (aq) C 11 H 22 O 11(s) C 11 H 22 O 11(aq) non-electrolytes electrolytes

Only hydrogens in very polar bonds are ionizable. (H must be bonded to a very electronegative element). Cl H H O H H H H H C C ++ δ+δ+ δ-δ- δ+δ+ δ-δ- + +-

Electrolytes are classified as strong and weak. Strong: produces many ions in solution - dissociates 100% in water. (NaCl) Weak: partially dissociates. Usually weak polar molecules. (household vinegar) A (s) B + (aq) + C – (aq)

ionic polar

ionicpolar

Strong acids easily donate protons - completely dissociate or ionize. Strong acids are strong electrolytes. HCl (s) H + (aq) + Cl - (aq) water Indicate complete dissociation using single arrow. [HCl] i = [H + ] e = [Cl - ] e

Name of Strong AcidFormula perchloric acidHClO 4 hydrochloric acidHCl sulfuric acidH 2 SO 4 nitric acidHNO 3 hydroiodic acidHI hydrobromic acidHBr

Weak acids are weak electrolytes. Weak acids incompletely ionize. Equilibrium between the ions and the molecules of acid. HC 2 H 3 O 2 + H 2 O H 3 O + + C 2 H 3 O 2 - acetic acid The reverse reaction is favored over the forward one. The ions formed react very easily to reform the acid and the water.

Name of Weak AcidFormula carbonic acidH 2 CO 3 hydrofluoric acidHF acetic acidHC 2 H 3 O 2 phosphoric acidH 3 PO 4

Strong bases are strong electrolytes. Strong bases dissociate into OH¯, or oxide, (O -2 ). NaOH (s) Na + (aq) + OH - (aq) water Indicate complete dissociation using single arrow. [NaOH] i = [Na + ] e = [OH - ] e

Basically, any hydroxide and Alkali (1A) or Alkali-Earth Metal (2A) would be a strong base because of 100% dissociation. Name of BaseFormula barium hydroxideBa(OH) 2 strontium hydroxideSr(OH) 2 lithium hydroxideLiOH

Weak bases are poor proton acceptors. Incompletely dissociate - form an equilibrium between the molecule and the ions formed. NH 3(g) + H 2 O (l) NH 4 + (aq) + OH - (aq) Does not produce hydroxide ions readily. The reverse reaction is favored.

Common weak bases are usually conjugate bases of strong acids. In fact: The weaker the acid, the stronger its conjugate base. The weaker the base, the stronger its conjugate acid. HA + H 2 O base acid H 3 O + + A - Con. baseCon. acid weak

Acid Strength Table

Any acid that contains only one ionizable hydrogen is called monoprotic. Contains two ionizable hydrogens - diprotic Three - triprotic Cl H H O O H O O s H O O H O O s p H Sulfuric acid Phosphoric acid

Acid Strength Table

The equilibrium reaction favours the strongest acid.

HCO 3 – + PO 4 3–  Which direction is favoured and why? HCO 3 – + PO 4 3–  CO 3 2– + HPO 4 2– acid 1 base 2 C base 1 C acid 2 fwd reaction is favoured HCO 3 – is the stronger acid

Don't confuse weak and strong with dilute and concentrated. Weak and strong indicates the proportion of an acid or base which ionized. Dilute and concentrated refer only to the volume of acid and base dissolved in a total solution volume. It is possible to have a concentrated weak acid/base or dilute strong acid/base

HAH + + A - HA + H 2 OH 3 O + + A - Strong Acid Weak Acid HA + H 2 O+ A - H+H+ H2OH2O H3O+H3O+

 Strong acids and bases are strong electrolytes.  Weak acids and bases are weak electrolytes.  Weak acids and bases partially ionize in water.  The stronger the acid, the weaker its conjugate base.  The stronger the base, the weaker its conjugate acid.  When acids and bases react, the stronger acid donates its proton and the stronger base accepts the proton.

CAN YOU / HAVE YOU?  Define electrolyte and explain the association with weak and strong.  Explain the difference between weak and strong acid and base.  Explain and compare dilute and concentrated solutions of acid or base.