Acids And Bases

Question 1

Bronsted lowry theory

Answer 1

Acid is a proton donor
Base is a proton acceptor

Question 2

What makes a strong acid

Answer 2

Acid which dissociates fully in solution
H2SO4
HCl
HNO3

Question 3

Weak acid

Answer 3

Only partially ionise in solution
Ethanoic acid
Usually covalent bonds

Question 4

Difference between alkali and base

Answer 4

An alkali is soluble in water and releases OH- ions
O2- + 2H+ -> H2O

Question 5

How to calculate pH

Answer 5

pH= -log[H+]

Question 6

What is kw

Answer 6

Ionic product of water
Kw= [H+][OH-]
Where kw=1.00×10^-14
Units mol2dm6

Question 7

What is ka

Answer 7

Equillibrium constant for weak acid dissociation
HA<=> H+ + A-
Units moldm3

Question 8

Dilutions

Answer 8

New concentration of solution= amount in moles of solute ÷ new total volume

Question 9

pH curve

Answer 9

Equivalence point: Rapid change in pH vertical inflection in curve
Volume where this occurs calculated with base volume needed to neutralise acid, vice versa

Question 10

Buffers

Answer 10

Solutions which resist changes in pH when small amounts of acid or base are added
Skin creams, anti ageing creams

Question 11

Acidic buffer

Answer 11

Formed from weak acid and it’s salt
When small amount of acid is added, extra H+ is added
Position of equillibrium HA <=> A- + H+ shifts left to remove excess H+
Keeps pH almost constant
When small amount of base added, extra OH- added
OH- reacts with H+ in buffer
Position of equillibbrium shifts right to increase H+
Keeps pH almost constant

Question 12

Basic buffers

Answer 12

Weak base and it’s salt
NH3 + H+ <=> NH4+
Small amount of acid added
Equillibrium shifts right
Small amounts of base added
OH- + H+ -> H2O
Equillibrium shifts left

Question 13

Preparation of acidic buffer

Answer 13

Add the weak acid and its salt together in solution
Or
Most common, add NaOH solution to excess weak acid