5.1.3 Acids, Bases and pH

Question 1

Brønsted-Lowry acid

Answer 1

Proton donor

Question 2

Brønsted-Lowry base

Answer 2

Proton acceptor

Question 3

Conjugate acid-base pair

Answer 3

2 species that can be interconverted by transfer of a proton (H+)

HCl(aq) + OH-(aq) ⇌ H2O(l) + Cl-(aq)
acid 1 base 2 acid 1 base 2

Question 4

Hydronium ion

Answer 4

H3O+

Question 5

Monobasic acids

Answer 5

An acid that can replace 1 H+ per molecule in an acid-base reaction 
(No. of H atoms in formula)
HCl = monobasic
H2CO3 = dibasic
H3PO4 = tribasic

Question 6

pH scale

Answer 6

pH=-log[H+(aq)]

[H+(aq)]= 10^-pH

Question 7

Strong acids

Answer 7

Completely dissociate in aqueous solution

[H+(aq)] = [HA(aq)]

Question 8

Weak acids

Answer 8

Partially dissociate in aqueous solution
Acid dissociation constant:
Ka= [H+(aq)]^2 / [HA(aq)]

Approximations:
[H+(aq)] = [A-(aq)]
[HA(aq)]start&raquo_space; [H+(aq)]eqm
[HA(aq)]eqm = [HA(aq)]start

Question 9

Acid dissociation constant

Answer 9

Ka = [H+(aq)][A-(aq)] / [HA(aq)]

pKa = -logKa
Ka = 10^-pKa

stronger acid = larger Ka value = smaller pKa value

Question 10

Ionic product of water

Answer 10

Kw = [H+(aq)] [OH-(aq)]
At 298K Kw= 1.00x10^-14 mol2dm-6
pH + pOH = 14