Topic 12: Acid-Base Equilibria

Question 1

Acids

Answer 1

H+ donors
always aqueous (H+ ions don’t exist on their own, bond with water)

Question 2

Conjugate acid-base pair

Answer 2

species formed when an acid donates a proton is its conjugate base
reaction is reversible
e.g: HCl + H2O ⇌ H3O + + Cl-
HCl and Cl- are a pair
H2O and H3O+ are a pair

Question 3

pH of acids

Answer 3

depends on [H+], more = lower pH
Monoprotic: one H+ per molecule e.g HCl
Diprotic: two H+ per molecule e.g H2SO4
at same concentration, diprotic have lower pH so are stronger

Question 4

pH formula

Answer 4

pH = -log[H+]
[H+] = 10^-pH

Question 5

Ionic product of water

Answer 5

some water can dissociate (reversible)
H2O ⇌ H+ + OH-
Kw = [H+][OH-]
at standard conditions (298K), Kw=1x10-14 mol2dom-6
at equilibrium: Kw = [H+]^2

Question 6

to calculate pH of mixture

Answer 6

calculate mols of [H+] and [OH-]
larger is in excess
final []is larger - smaller, then use Kw or -log