1. 8.1 Explaining the Properties of Acids & Bases
SCH4U - Chemistry, Gr. 12, University Prep
Ms. Papaiconomou & Ms. Lorenowicz

2. Common Properties of Acids & Bases
Property
Acid
Base
Taste
Sour
Bitter
Texture of Solution
No characteristic texture
Slippery
Aqueous Property of Oxides
Non-metal oxides form acidic solutions:
CO2(g) + H2O(l)  H2CO3(aq)
Metal oxides form basic solutions:
CaO(g) + H2O(l)  Ca(OH)2(aq)
Reaction with Phenolphthalein
Colourless
Pink
Reaction with litmus paper
Blue litmus  Red
Red litmus  Blue
Reaction with Metals
Acids react with metals above H in the activity series to displace H2(g)
Bases react with certain metals (i.e. Al) to form H2(g)
Reaction with CO32-
Form CO2(g)
No reaction
Reaction with NH4Cl
Form NH3
Reaction with Fatty Acids
React to form soap (saponification reaction)
Neutralization Reactions
Acid + Base  Water + Salt

3. Arrhenius Theory of Acids & Bases (Arrhenius, 1887)
Acids & bases are defined in terms of their structure and the ions produced when they dissolve in water.
Explains acid-base reactions and neutralization.
ACID: dissociates in water to form H+(aq)
HCl (hydrochloric acid), H2SO4 (sulphuric acid)
BASE: dissociates in water to form OH-(aq)
NaOH (sodium hydroxide), KOH (potassium hydroxide)
LIMITATIONS:
hydrogen ion combines with water to form hydronium ion
does not explain some bases (i.e. ammonia, salt solutions)
does not explain acid-base reactions without water (i.e. gas)

4. Brønsted-Lowry Theory (Johannes Brønsted & Thomas Lowry, 1923)
Recognizes an acid-base reaction as chemical equilibrium, have a forward and reverse reaction involving the transfer of a proton
ACID: substance from which a proton can be removed
“proton-donor”
BASE: substance that can accept a proton
“proton-acceptor”
proton = nucleus of a hydrogen atom (H+ ion)
acid base conjugate conjugate
acid base

5. Conjugate Acid-Base Pairs
base acid conjugate conjugate
acid base
dissociation is an equilibrium reaction because it proceeds in both directions
H2O donates a proton in forward rxn  acid
OH- accepts a proton in reverse rxn  conjugate base
If a substance acts as a proton donor and a proton accepter, it is termed “amphoteric” (i.e. water)

6. Strong Acids
Completely dissociates in water (equilibrium favours products, lies to the right)
Binary acids [HX(aq) where X = Cl, Br, I (not F)]
Factors:
Across period: electronegativity
Down a group: bond strength
Oxoacids (contain oxygen atoms) where the # [O] > # H (by 2 or more)
Number of oxygen atoms
Monoprotic
only have single H atom that dissociates
Polyprotic
have more than 1 H atom that dissociates
Strength decreases as number of hydrogen atoms that have dissociated increases

7. Strong Bases
Completely dissociates in water (equilibrium favours products, lies to the right)
Oxides & Hydroxides of alkali metals (Group 1) and of of alkali earth metals (Group 2) below beryllium [e.g. NaOH sodium hydroxide, MgO magnesium oxide]
Factors:
Metals with low electronegativity form ionic bonds with oxygen  easily break bond with oxygen which reacts with water to form hydroxide ions

8. Calculations that involve strong acids & bases
Strong acids/bases (and strong electrolytes) completely dissociates into ions in water
[H3O]+(aq) is equal to the [strong acid]
[OH]-(aq) is equal to the [strong base]
You cannot determine the concentrations of ions of weak acids/bases/electrolytes this way because they do not completely dissociate in solution (more next class)

9. Homework Please re-read Section 8.1(pp.377-387) and answer:
p.382 Q.1-4
p.386 Q.5-8
p.387 Q.1-5