Acids, Bases, and Buffers

Question 1

Acids

Answer 1

Proton donors

Question 2

Bases

Answer 2

Proton acceptors

Question 3

Monotropic Acid

Answer 3

Can donate one mole of protons per mole of acid
e.g. HCl

Question 4

Diprotic Acids

Answer 4

Can donate two moles of protons per mole of acid
e.g. H2SO4

Question 5

Strong acids

Answer 5

Dissociate completely in water

Question 6

Strong bases

Answer 6

Ionise completely in water
e.g. NaOH and KOH

Question 7

Weak acids

Answer 7

Dissociate weakly in water

Question 8

Weak bases

Answer 8

Ionise weakly in water

Question 9

Water can act as either:

Answer 9

Acid- donates proton
Base- accepts proton

Question 10

Water dissociates into:

Answer 10

Hydroxonium ions H3O+
Hydroxide ions OH-

Question 11

Ionic product of water

Answer 11

Kw = [H+] [OH-]

Question 12

Effect of increasing temperature on Kw

Answer 12

Kw increases
pH decreases
Equilibrium moves to the right

Question 13

pH scale

Answer 13

Measure of H+ present in a solution

Question 14

pH

Answer 14

-log[H+]

Question 15

[H+]

Answer 15

10^-pH

Question 16

Weak acids and Weak bases in aqueous solution

Answer 16

Dissociate slightly

Question 17

Concentration

Answer 17

Amount of acid in moles per cubic meter (mol dm-3)

Question 18

Strength of an Acid

Answer 18

Extent to which it ionises

Question 19

Acid dissociation constant

Answer 19

Ka = [H+] ^2 / [HA]

Question 20

pKa

Answer 20

pKa = - log(Ka)

Question 21

Ka

Answer 21

10^ -pKa

Question 22

Equivalence Point

Answer 22

Colour change when mixing two solutions in equal proportion (vertical line) neutralisation occurs here

Question 23

Methyl Orange

Answer 23

Red ——-> Yellow
Colour change: 3.1 - 4.4

Question 24

Phenolphthalein

Answer 24

Colourless —–> Pink
Colour change: 8.3 - 10

Question 25

Indicator for Strong Acid / Strong Base

Answer 25

Methyl Orange
Phenolphthalein

Question 26

Indicator for Strong Acid / Weak Base

Answer 26

Methyl Orange

Question 27

Indicator for Weak Acid / Strong Base

Answer 27

Phenolphthalein

Question 28

Indicator for Weak Acid / Weak Base

Answer 28

None - no sharp pH change

Question 29

Buffer

Answer 29

Chemical that resists change in pH when a small amount of acid or base is added

Question 30

Acidic Buffer

Answer 30

Resists change in pH to keep the pH below pH 7, made from weak acid and its salt

Question 31

Basic Buffer

Answer 31

Resists change in pH to keep the pH above pH 7, made from a weak base and its salt

Question 32

Salt dissociation

Answer 32

Dissociate strongly

Question 33

Uses of buffers

Answer 33

Shampoo
Washing powder
Blood

Question 34

Why is H2O not shown in Kw = [H+][OH-]

Answer 34

Water is almost always constant

Question 35

Why is pH probe washed with distilled water in between calibration measurements?

Answer 35

Different solutions must not contaminate eachother

Question 36

Why do we add small amounts of solution (e.g. NaOH) between each measurement when we are measuring the pH?

Answer 36

To avoid missing the end point