1 pH, acids, bases + buffers

Question 1

what is Mr?

Answer 1

relative molecular mass

Question 2

what is Ar?

Answer 2

relative atomic mass

Question 3

define Mr

Answer 3

the mean mass of a molecule of a compound / 1/12 mean mass of a c12 isotope

Question 4

define Ar

Answer 4

the mean mass of an atom of an element / 1/12 mean mass of a c12 isotope

Question 5

what is avogadro’s number and what is its definition?

Answer 5

6.022 x 10^23
number of particles in one mole of a substance

Question 6

what is the triangle for the moles mass and Mr equation?

Answer 6

mass
mol Mr

Question 7

what is the triangle for the concentration moles and volume equation?

Answer 7

moles
conc vol

Question 8

what is the general definition of an acid?

Answer 8

a substance that increases the concentration of H+ ions when dissolved in water

Question 9

what is the general definition of a base?

Answer 9

a substance that increases the concentration of OH- ions when dissolved in water

Question 10

define a bronsted lowry acid

Answer 10

proton donor

Question 11

define a bronsted lowry base

Answer 11

proton acceptor

Question 12

what is a conjugate acid?

Answer 12

species formed when a base gains a proton

Question 13

what is a conjugate base?

Answer 13

species formed when an acid loses a proton

Question 14

how do conjugate acids and bases differ?

Answer 14

the conjugate acid always has ONE extra proton more than the conjugate base

Question 15

what do strong acids do in water?

Answer 15

completely dissociate

Question 16

what do weak acids do in water?

Answer 16

partially dissociate

Question 17

describe a strong acids conjugate base

Answer 17

non basic / very weak

Question 18

describe a weak acids conjugate base

Answer 18

just weak

Question 19

what do you use to measure pH?

Answer 19

• litmus paper
• indicator

Question 20

what is the equation for pH?

Answer 20

pH = -log10 [H+]

Question 21

what is the equation for pOH?

Answer 21

pOH = -log10 [OH-]

Question 22

how do you calculate Ka?

Answer 22

Ka = [H+][A-] / [HA]

Question 23

what is Ka?

Answer 23

acid dissociation constant

Question 24

what is Ka used for?

Answer 24

working out the pH of a weak acid

Question 25

what is the equation for pKa?

Answer 25

pKa = -log10 [Ka]

Question 26

what is pKa used for?

Answer 26

working out the strength of a weak acid

Question 27

how would you work out [H+] if you know the Ka and the concentration?

Answer 27

[H+] = square root of Ka x concentration

Question 28

define a weak acid / base

Answer 28

not completely ionised in aqueous solution

Question 29

define a buffer

Answer 29

any solution that resists a change to pH when a small amount of an acid or a base are added

Question 30

what makes an acidic buffer?

Answer 30

a weak acid and its conjugate base as a salt

Question 31

what makes a basic buffer?

Answer 31

a weak base and its conjugate acid as a salt

Question 32

where does an acidic buffer sit on the pH scale?

Answer 32

buffers on acidic side of neutral

Question 33

where does a basic buffer sit on the pH scale?

Answer 33

buffers on the basic side of neutral

Question 34

how do you calculate the pH with henderson hasselbalch?

Answer 34

pH = pKa + log10 x [salt] / [acid]