Topic 11: Acids and Bases

Question 1

Define acids and bases in different definitions

Answer 1

• Acids: many common types have a proton attached to an O atom (H proton attached to very electronegative O)
  + H+ producer in aqueous solution
  + H+/proton donor
• Bases: many bases have a free OH- for N atom with 1 lone pair
  + OH- producer in aqueous solution
  + H+/proton acceptor

Question 2

Explain equilibrium change in strong acid and weak acid in aqueous solution

Answer 2

• Strong acid: fully dissociated in aqueous solution → equilibrium favor mostly the right side
• Weak acid: partly/mostly intact → equilibrium favor mostly the left side

Question 3

Explain conjugate acid-base pair

Answer 3

A conjugate base has 1 fewer proton than its conjugate acid

Question 4

What is a diprotic acid and give an example?

Answer 4

A diprotic acid may have a conjugate base that has another conjugate base.
e.g. H2SO4

Question 5

How is pH and pOH calculated and related to each other?

Answer 5

pH = -log10[H+]
pOH = -log10[OH-]
pH + pOH = 14

Question 6

What is Kw?

Answer 6

Water ionisation constant

Kw = [H3O+][OH-]

Question 7

When is Kw = 1*10^-14 and how does temperature affect Kw?

Answer 7

Kw = 1*10^-14 only when T=25 Celcius

T > 25 -> Kw > 10^-14
T < 25 -> Kw < 10^-14