Acids And Bases

Front 1

Bronsted lowry acid

Back 1

Proton donor

Front 2

Bronsted lowry base

Back 2

Proton acceptor

Front 3

Strong acids and bases

Back 3

Completely dissociate into ions in aqueous solution

Front 4

Weak acids and bases

Back 4

Partially dissociate into ions in aqueous solution (eq lies to the left)

Front 5

Addition of water to an acid

Back 5

HA + H2O > H3O+ + A-

Front 6

Addition of water to a base

Back 6

NH3 + H20 > NH4+ + OH-

Front 7

Define pH

Back 7

-log10[H+] inverse proportion

Front 8

Ionic product of water

Back 8

Kw= [H+][OH-]

1×10-14 at 298K

Front 9

Kw and temperature

Back 9

Increases with temperature because the dissociation of water, which involves the breaking of covalent bonds, is endothermic

pH decreases

Front 10

Pure water

Back 10

[H+] = [OH-]

SO Kw = [H+]2

Front 11

pH of strong acid/strong base

Back 11

[H+] = Kw/[OH-]

Then pH equation

Front 12

Diluting strong acid/strong base

Back 12

Calculate moles of H+/OH-

Covert to concentration by dividing by new volume

Find H+ if necessary

pH equation

Front 13

Strong acid-strong base calculations

Back 13

Moles of H+ and OH-

Find excess moles

Divide by total volume

Find [H+]?

pH

Front 14

Ka equation

Back 14

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

For a weak acid we can assume that

Ka = [H+]2 / [HA] if it is added to water

Front 15

Weak acid-strong base calculations

Back 15

Calculate HA and strong base moles

Find excess moles

Acid: put in Ka to find [H+] and pH

Base: divide by total volume, put in Kw then find pH

Front 16

Calibrating pH meter

Back 16

• Rinse probe with deionised, dry and place in pH 4 buffer solution

• Wait for reading to remain steady, then set pH meter to 4

• Take probe out, rinse with deionised, dry and place in pH 10 buffer solution

• Wait for reading to remain steady,then set pH meter to 10

Front 17

pH titrations

Back 17

• measure pH before any solution is added from the burette

• add solution from burette 1cm3 at a time

• stir mixture

• record pH after each addition

• add solution from burette 0.1cm3 at a time near endpoint

• after endpoint add solution from burette 1cm3 at a time until in excess

Front 18

Features of a pH curve

Back 18

Initial pH

Equivalence point

pH range at equivalence

Final pH

Front 19

Strong acid-strong base pH range

Back 19

3 to 11

Front 20

Weak acid-strong base pH range

Back 20

7 to 11

Levels off quickly due to formation of salt causing a buffer

Front 21

Strong acid-weak base pH range

Back 21

3 to 7

Front 22

Weak acid-weak base range

Back 22

7

Front 23

Half neutralization point

Back 23

Half way between 0 and equivalence point

Where [HA] = [A-]

pH = pKa

Front 24

Properties of an indicator

Back 24

Sharp colour change (no more than 1 drop)

End point given must be equivalence point

Distinct colour change

Front 25

Methyl orange

Back 25

Red in acid, yellow in alkali

pKa= 3.7

Range 3-5

Front 26

Phenolphthalein

Back 26

Cloudless in acid

Pink in alkali

pKa = 9.3

pH range = 8-10

Front 27

Acidic buffers

Back 27

Maintains solution at a pH below 7

Weak acid+salt

Weak acid+strong base

Front 28

Basic buffer

Back 28

Maintains solution at pH 7 or above

Weak base and salt

Front 29

Adding acid to acidic buffer

Back 29

HA 》《 H+ + A-

Added H+ reacts with A-

Acid eqm shifts to left to decrease H+

Ratio of [HA] remains constant

Front 30

Adding base to acidic buffer

Back 30

HA 《》 H+ + OH-

Added OH- reacts with H+

Acid eqm shifts to right to replace H+

Ratio of [HA] remains constant

Front 31

Adding acid to basic buffer

Back 31

NH3 + H20 《》 NH4+ + OH-

Added H+ reacts with OH- eqm shifts to right to replace H+

Front 32

Adding base to basic buffer

Back 32

NH3 + H2O 《》 NH4+ + OH-

Added OH- reacts with NH4+

Eqm shifts to left to decrease OH-

Front 33

Weak acid salt buffer calculation

Back 33

Ka= [H+] [salt] / [moles of acid]

Front 34

Weak acid strong base buffer calculation

Back 34

Ka= [H+] [OH-]/ [excess acid moles]

Front 35

Adding strong base to buffer

Back 35

Decreases HA moles

Increases A- moles

Front 36

Adding strong acid to buffer

Back 36

Increases HA moles

Decreases A- moles

Front 37

Suggest why pure water isnt acidic

Back 37

[H+] = [OH-]

Front 38

Suggest a substance that could be added to aqueous methylamine to produce a basic buffer

Back 38

CH3NH3Cl

Front 39

Define buffer

Back 39

Solution which maintains pH despite the addition of an acid or a base