Acids, Bases & Buffers

Front 1

What definition of an acid is this?

"A proton (H+) donor"

Back 1

Brønsted-Lowry

Front 2

What is the Brønsted-Lowry definition of a base?

Back 2

A base is a proton acceptor

Front 3

What is another name for a monobasic acid?

Back 3

Monoprotic

Front 4

What is a monobasic acid?

Back 4

An acid that can release one proton per molecule when it dissociates in water.

Front 5

How many moles of OH- does a monobasic acid require to neutralise it?

Back 5

1 mole

Front 6

What is a dibasic acid?

Back 6

An acid that can release two protons per molecule when it dissociates in water.

Front 7

What is a tribasic acid?

Back 7

An acid that can release three protons per molecule when it dissociates in water.

Front 8

How many moles of OH- ions does one mole of tribasic acid require to neutralise it?

Back 8

three moles

Front 9

When can an acid act as a proton donor/

Back 9

When an acid is added to water.

Front 10

What is the difference between a strong and a weak acid?

Back 10

A strong acid completely dissociates into its ions in solution. A weak acid partially dissociates into its ions in solution.

Front 11

what is the difference in writing an equation for dissociation of a weak acid and a strong acid?

Back 11

Strong acid arrow facing forwards

A weak acid reaches an equilibrium this type of arrow.

Front 12

What bond breaks when HCl dissolves in water?

Back 12

H-Cl bond.

Front 13

HCl(aq) + H2O(l) ---> H3O+ + Cl-

In this reaction which out of HCl and H2O acts as the acid?(and why?)

Back 13

HCl is an acid as it donates a proton to water to form a chloride ion.

Front 14

HCl(aq) + H2O(l) ---> H3O+ + Cl-

Which out of HCl and H2O acts as a base and why?

Back 14

H2O as it accepts a proton from HCl to form H3O+ ion

Front 15

What is the name of H3O-?

Back 15

oxonium ion

Front 16

In the dissociation of ethanoic acid, which moelcule acts as a base and accepts a proton?

Back 16

ethanoate ion

Front 17

What is a conjugate acid-base pair?

Back 17

A pair of two species that transform into each other by the loss or gain of a proton (H+).

Front 18

HCl(aq) + H2O(l) <---> H3O+ + Cl-

In this reaction name the conjugate pairs.

Back 18

HCl(acid) and Cl- (base)

H3O+ (acid) and H2O (base)

Front 19

Which species in a conjugate pair will act as an acid?

Back 19

The species richer in protons.

Front 20

In a conjugate base pair what do the pair differ by?

Back 20

1 proton (H+)

Front 21

If two acids are reacted together which one acts as an acid and which one acts as a base?

Back 21

Stronger acid donates protons and the weaker acid accepts protons (acts as a base)

Front 22

In a strong acid why is only a forwards reaction arrow drawn?

Back 22

The equilibrium positionis so far too the right that the reverse reaction is insignificant. Dissociation is complete and the concentration of protons is high.

Front 23

Where does the equilibrium position lie in a weak acid?

Back 23

Far too the left meaning the reverse reaction is significant.

Front 24

What is the concentration of protons like in a weak acid?

Back 24

Low compared with concentration of undissociated CH3COOH

Front 25

What is the ionic equation for a metal e.g. magnesium and acid?

Back 25

Mg(s) + 2H+(aq) -------> Mg2+ + H2(g)

Front 26

What is the ionic equation between metal oxide and acid?

Back 26

O2-(s) +2H+(aq) -----> H2O(l)

Front 27

What is the ionic equation between metal hydroxide and acid?

Back 27

OH-(aq) + H+(aq) ------>H2O(l)

Front 28

What is the ionic equation between metal carbonate and acid?

Back 28

CO32-(s) + 2H+(aq) -------> CO2(g) + H2O(l)

Front 29

What is the ionic equation for ammonia and acid?

Back 29

NH3(aq) + H+(aq) -----> NH4+(aq)

Front 30

Name 5 strong acids:

Back 30

HCl(aq)

HBr(aq)

HI(aq)

HNO3(aq)

H2SO4 (aq)

Front 31

Name two strong bases:

Back 31

NaOH(aq)

KOH(aq)

Front 32

Name two weak bases?

Back 32

Ammonia

amines RNH2(aq)

Front 33

Name two weak acids including one group:

Back 33

carboxylic acids

Phenol

Front 34

What is the formula for the functional group of amines?

Back 34

RNH2(aq)

Front 35

What type of equilibrium is the dissociation of a weak acid in water?

Back 35

homogenous equilibrium

Front 36

What is the equation for Ka?

Back 36

Front 37

What are the units for Ka (With a monobasic acid)?

Back 37

moldm^-3

Front 38

What is Ka and what does it mean?

Back 38

Acid dissociation constant Ka indicates the extent(degree) of acid dissociation.

Front 39

What does a large Ka value suggest about an acid?

Back 39

Strong acid

[H+] and [A-] are large and the equilibrium position is far to the right. A lot of HA(aq) acid is dissociated into its ions.

Front 40

What does it suggest if Ka is a small number?

Back 40

Weak acid. [H+] and [A-] are small. The equilibrium position is far to the left. A lot of HA is not dissociated.

Front 41

How do you calculate pKa?

Back 41

-logKa

Front 42

What does "pX" mean?

Back 42

-logx

Front 43

How would you convert pKa into Ka?

Back 43

Ka=10^-pKa

Front 44

Why are pKa values often used instead of Ka?

Back 44

Ka values can be very small or very large.

Front 45

What does a small pKa value mean?

Back 45

Strong acid

Front 46

What does a small Ka value mean?

Back 46

weak acid.

Front 47

What does a large Ka value mean?

Back 47

strong acid

Front 48

What does a large pKa value mean?

Back 48

weak acid

Front 49

Which out of HCl and CH3COOH would have the large pKa value and why?

Back 49

CH3COOH as it is the weaker acid (has small Ka value).

Front 50

How do you convert between pKa and Ka?

Back 50

Front 51

What do Ka values only depend on?

Back 51

Temperature as with all equilibrium constants.

Front 52

What does Kw mean?

Back 52

Ionic product of water

Front 53

What is the equation for self-ionisation of water?

Back 53

Front 54

What s another name for self-ionisation?

Back 54

self-dissociation

Front 55

What type of equilibrium is the self-ionisation of water and why?

Back 55

heterogeneous equilibrium as the reactants and products are in different states.

Front 56

What are teh units for Kw?

Back 56

mol^2dm^-6

Front 57

What is the equation for Kw?

Back 57

Kw=[H+][OH-]

Front 58

Why is H2O not written in the expression for Kw?

Back 58

It is considered constant for ionic equilibria

Front 59

What does Kw only depend on?

Back 59

temperature.

Front 60

What is Kw at 25C?

Back 60

1.00x10^-14 mol^2dm^-6

Front 61

What is the definition for pH?

Back 61

pH=-log[H+]

Front 62

What type of scale is pH scale?

Back 62

logarithmic

Front 63

How would you calculate [H+] from pH?

Back 63

[H+]=10^-pH

Front 64

Use equatiosn to show relationship between [H+] and [OH-] in acidic solutions?

Back 64

[H+] > [OH-]

Front 65

Use equation to show relationship between [H+] and [OH-] in basic solutions:

Back 65

[H+] < [OH-]

Front 66

What is relationship between [OH-] and [H+] in neutral solution?

Back 66

[H+]=[OH-]

Front 67

What does [OH-][H+] equal? (at 25C)

Back 67

Kw 1.00x10^-14

Front 68

How would you use the expression for Kw to calculate the concentration of OH- ions?

Back 68

[OH-] =Kw/ [H+]

Front 69

What does [H+] equal in a strong monobasic acid in aqueous solution and why?

Back 69

[HA]=[H+] as the acid completely dissociates

Front 70

How would you calculate pH of a strong monobasic acid in aqueous solution?

Back 70

-log[HA] as [HA]=[H+]

Front 71

Why can the pH of a weak acid not be calculated in the same way as a strong acid?

Back 71

Weak acid only partially dissociates into its ions in solution

Front 72

What assumptions are made in order to calculate an approximation of pH of weak acids?

Back 72

A large proportion of acid remains undissociated tehrefore