Acids, bases and buffers

Question 1

what are Bronstead Lowry acids

Answer 1

proton donors

Question 2

what do H+ ions form in water

Answer 2

hydroxonium ions

Question 3

what are Bronsted Lowry bases

Answer 3

proton donors

Question 4

what is called when an acid can donate more than one proton and give examples

Answer 4

polyprotic
nitric acid
sulphuric acid
phosphoric acid

Question 5

acids react with bases to form _______ which are pH _____

Answer 5

salts pH

Question 6

what is a conjugate pair linked by

Answer 6

transfer of a proton

Question 7

any species that has gained a proton is a conjugate _____ and any species which has lost a proton is a conjugate ______

Answer 7

acid, base

Question 8

when a strong acid or base is present the forward or backward reaction is favoured? and more ions are produced

Answer 8

forward

Question 9

what is the equation for Kw

Answer 9

Kw= (H+)(OH-)

Question 10

how do you calculate pH

Answer 10

pH= -log10 (H+)

Question 11

how do you calculate conc. of H+ ions

Answer 11

= 10^-ph

Question 12

monoprotic acids dissociate to produce one H+ ion for every acid molecule, this means that

Answer 12

conc of the acid= conc of H+ ions

Question 13

diuretic acids dissociate to produce two H+ ions for every acid molecule this means that

Answer 13

conc of acid= 2 x conc of H+ ions

Question 14

weak acids only dissociate slightly in aqueous solutions so what constant is used to work out their pH

Answer 14

Ka

Question 15

what are the two assumptions made when calculating Ka of a weak acid

Answer 15

only a small amount of weak acid dissociates
(conc of weak acid at equilibrium)= (conc of weak cid at start)
the dissociation of acid is greater than the dissociation of water so all H+ ions come from acid
H+ conc= A-

Question 16

what is the calculation for pKa

Answer 16

pKa= -log10Ka

Question 17

what is the calculation for Ka using pKa

Answer 17

10^-pKa

Question 18

when using a ph probe what must you do first

Answer 18

place in distilled water

Question 19

draw titration curve for a strong acid and strong base

Question 20

draw titration curve for strong acid weak base

Question 21

draw titration curve for weak acid strong base

Question 22

draw titration curve for weak acid weak base

Question 23

what is the equivalence point on a titration curve

Answer 23

when the acid has been fully neutralised by the base
H+ conc= OH- conc

Question 24

what must you look at on a titration curve when choosing a suitable indicator

Answer 24

the vertical part

Question 25

when can methyl orange be used as indicator and what is its colour change

Answer 25

red at low pH, yellow at high
strong acid, weak base
strong acid, strong base

Question 26

when can phenolphthalein be used as an indicator and what is its colour change

Answer 26

colourless at low ph, pink at high ph
weak acid, strong base

Question 27

what is a buffer solution

Answer 27

system that minimises pH changes on addition of small amounts of an acid or a base

Question 28

how do you calculate the pH of a buffer

Answer 28

1. write equation and Ka expression
2. rearrange question to get H+ conc
3. calculate H+
4. calculate ph using -log (H+)

Question 29

how are buffers used in the blood

Answer 29

blood pH should be maintained at 7.4
H2CO3——H+ + HCO3-
H2CO3——– H2O+ CO2
when we breathe out CO2 the level of carbonic acid reduces as equilibrium shifts to the right to attempt to replace them