5.3.1 Acids, Bases and pH

Question 1

strong acid definition

Answer 1

good proton donator
dissocisate completely to form ions in aqueous solution

Question 2

monobasic acid definition

Answer 2

1 H+ ion can be replaced per molecule in an acid base reaction

Question 3

what are H+ ions typically replaced by

Answer 3

metal or ammonium ion

Question 4

example of monobasic acid

Answer 4

HCl

Question 5

Dibasic acid

Answer 5

can have 2 protons replaced when they react with bases

Question 6

example of dibasic acid

Answer 6

H2SO4

Question 7

what is an acid in terms of protons

Answer 7

proton donor

Question 8

what is a base in terms of protons

Answer 8

proton acceptor

Question 9

conjugate acid-base pair

Answer 9

2 species can be interconverted by transfer of a proton

Question 10

what is pH

Answer 10

measure of how many H+ ions are present in the solution
i.e concentration

Question 11

pH =

Answer 11

-log[H+(aq)]

Question 12

[H+]

Answer 12

10^-pH

Question 13

weak acid definition

Answer 13

poor proton donors, partially dissociate into ion when in solution

Question 14

where does equilibrium lie for a weak acid and why
HA<-> H+ + A-

Answer 14

lies to the left due to some of the acid not dissociating yet as it only partially dissociates

Question 15

Ka equation for
HA<-> H+ + A-

Answer 15

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

Question 16

pKa =

Answer 16

-log(Ka)

Question 17

what is pKa

Answer 17

way of measuring strength of an acid

Question 18

what type of acid is it if it has a low pKa

Answer 18

stronger acid

Question 19

strong base

Answer 19

dissociates completely

Question 20

if you have a low [H+] what pH value would it be

Answer 20

high pH

Question 21

how many times is the concentration of H+ ions in pH1 than pH2

Answer 21

10 times greater

Question 22

what would the dilution be to get a solution from pH 1 to pH4

Answer 22

10 x 10 x 10 = 1000

Question 23

units for [H+]

Answer 23

mol dm-3

Question 24

what does a larger Ka value show

Answer 24

equilibrium is to the right
the greater the dissociation and the greater the acid strength

Question 25

what is the Ka and type of acid if the pKa vaue is high

Answer 25

weaker acid
smaller Ka value

Question 26

what does [H+(aq)] depend on

Answer 26

concentration of acid
acid dissociation constant Ka

Question 27

what is the acid dissociation curve

Answer 27

Ka

Question 28

how do you calculate pH from the Ka expression

Answer 28

make [H+] the subject of Ka expression
then use pH = -log[H+]

Question 29

how to experimentally determine the Ka for a weak acid

Answer 29

• prepare standard solution of the weak acid of known concentration
• measure the pH of the standard solution using pH meter

Question 30

Ka equation for treating water as a weak acid

Answer 30

[H+][OH-] / [H2O]

Question 31

what is the ionic product of water

Answer 31

Kw
ions in water multiplied together

Question 32

definition of an alkali

Answer 32

soluble base that releases OH- ions in aqueous solution

Question 33

define pH

Answer 33

-log[H+]

Question 34

what are the assumptions made when using Ka

Answer 34

[HA] doesn’t decrease when partial dissociation occurs - innacurate pH calculation for stronger weak acids
ignores dissociation of water- relevant for very weak acids

Question 35

how to work out pH for solutions made with acid and base

Answer 35

work out moles of each
find the difference
work out concentration of the difference
do -log[H+]
if the base is in excess then you’ve worked out pOH so then minus that from 14

Question 36

when working out pH for solution what do you do if one is a dibasicacid

Answer 36

multiply number of moles by 2