Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

A Level Physical Chemistry > 1.12 Acids and Bases > Flashcards

1.12 Acids and Bases Flashcards

1
Q

Define a Brønsted-Lowry acid

A

Proton donor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Define a Brønsted-Lowry base

A

Proton acceptor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What ion causes a solution to be acidic? (2 answers) Name and formula

A

H+ (hydrogen ion) or more accurately, H3O+ (oxonium ion) as protons react with H2O to form it

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What ion causes a solution to be alkaline?

A

-OH (hydroxide ion)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Write an equation for the ionisation of water (2)

A

2H2O (l) ⇌ H3O+ (aq) + -OH(aq)
OR H2O(l) ⇌ H+ (aq) + -OH(aq)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Derive Kw using the equation for ionisation of water

A

Slide 14

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the value of Kw at 298K?

A

1.0 x 10^-14

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What physical factors affect the value of Kw? How do they affect it?

A

Temperature only- when temperature is increased, the equilibrium moves to the right so Kw increases and the pH of pure water decreases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Why is pure water still neutral, even if pH does not equal 7?

A

[H+]=[-OH]

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Give an expression for pH in terms of H+

A

pH = -log10[H+]

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is the relationship between pH and concentration of H+?

A

Lower pH = higher concentration of H+

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

If two solutions have a pH difference of 1, what is the difference in [H+]?

A

A factor of 10

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How do you find [H+] from pH?

A

[H+] = 10^-pH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

How do you find [OH-] from pH? (at 298K)

A

Find [H+], use Kw (equal to 1 x 10^-14 at 298K) to calculate [-OH]

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is different when finding [H+] from the concentration of diprotic and tripotic acids?

A

Need to multiply the concentration of the acid by the number of protons to find [H+]

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How do you calculate the pH of a strong alkaline solution?

A

Use Kw to calculate [H+] from [OH-]

Use pH = -log[H+]

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Define the term strong acid

A

One which fully dissociates in water (HX —> H+ + X-)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Define the term strong base

A

One which fully dissociates in water (XOH —> X+ + -OH)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is the difference between concentration and strong?

A

Concentrated means many mol per dm^3, strong refers to amount of dissociation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is a weak acid and a weak base

A

Weak acids and bases do not fully dissociates in water. They only partially dissociate into their ions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Give some examples of strong acids

A

HCl, H2SO4, H3PO4

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Give some examples of strong bases

A

NaOH, CaCO3, Na2CO3

23
Q

Give some examples of weak acids

A

CH3COOH (ethanoic), any organic acid

24
Q

Give some examples of weak bases

A

NH3

25
Q

What is a Ka? (Expression)

A
26
Q

How would you work out the pH of a weak acid?

A

Use the equation for Ka, subbing in values for [A-] and [HA]

Use pH=-log[H+] equation to find pH

27
Q

What is a titration

A

The addition of an acid/base of know titration to a base/acid of unknown titration to determine the concentration. Am indicator is used to show that neutralisation has occurred, as is a pH meter

28
Q

Draw a diagram of the equipment that could be used for a titration

A

Draw a diagram of the equipment that could be used for a titration

29
Q

Draw the titration curve for a strong acid with a strong base added

A
30
Q

Draw the titration curve for a strong acid with a weak base added

A
31
Q

Draw the titration curve for a strong acid with a weak base added

A
32
Q

Draw the titration curve for a strong acid with a strong base added

A
33
Q

Define the term equivalence point

A

The point at which the exact volume of base has been added to just neutralise the acid, or vice-versa

34
Q

What generally happens to the pH of the solution around the equivalence point?

A

There is a large and rapid change in pH, except in the weak-weak titration

35
Q

How would you calculate the concentration of a reactant if you know the volume and concentration of the other reactant and the volume of that reactant added

A

Calculate mols of one reactant

Use balance equation to work out mols of the other

Use conc=mol/vol to calculate concentration

36
Q

What Is the end point?

A

The volume of acid or alkali added when the indicator just changes colour. If the right indicator is chosen, equivalent point = end point

37
Q

What are the properties of a good indicator for a reaction? (3)

A

Sharp colour change - no more than one drop of acid/alkali needed for colour change

End point must be the same as the equivalence point, or titration gives wrong answer

Distinct colour change so it is obvious when the end point has been reached

38
Q

What indicator would you use for a strong acid-strong base titration?

A

Phenolphthalein or methyl orange, but phenolphthalein is usually used as clearer colour change

39
Q

What indicator would you use for a strong acid-weak base titration?

A

Methyl orange

40
Q

What indicator would you use for a strong base-weak acid titration?

A

Phenolphthalein

41
Q

What indicator would you use from a weak acid-weak base titration

A

Neither methyl orange or phenolphthalein is suitable, as neither give a sharp change at the end point

42
Q

What colour is methyl orange in acid? In alkali? At what pH does it change?

A

Red in acid; yellow in alkali. Changes at about pH= 4-5. Approx same as pKa value

43
Q

What colour is phenolphthalein in acid? In alkali? At what pH does it change?

A

Colourless in acid; red in alkali. Changes at about pH= 9-10. Approx same as pKa value

44
Q

What is the half-neutralisation point

A

When volume = half the volume that has been added at the equivalence point

45
Q

Define a buffer solution

A

A solution that resist changes in pH when small amount of acid/alkali are added

46
Q

What do acidic buffer solutions contain in general terms?

A

A weak acid and a soluble salt of that acid that fully dissociates

47
Q

Write a reaction for an acidic buffer with added acid

A

A- + H+ —> HA, opposes addition of H+

48
Q

Write a reaction for an acidic buffer with added alkali

A

HA + OH- —> H2O + A-

49
Q

How else can you achieve an acidic buffer solution other than just mixing the constituents?

A

Neutralise half of a week acid (meaning the acid must be in excess) with an alkali - this forms a weak acid / soluble salt mixture

50
Q

What do basic buffer solutions contain in general terms?

A

Weak base and soluble salt of that weak base

51
Q

How can you calculate the pH of buffer solutions?

A

Use the Ka of the weak acid, sub in [A- and [HA], calculate [H+] —> pH

52
Q

How can you calculate the new pH of a buffer solution when acid or base is added?

A

Calculate number of moles of H+ and A- and HA before acid or base is added. Use the equations to work out new moles of A- and HA —> find [H+] —> pH

53
Q

Which buffer system maintains blood pH at 7.4? What happens when acid/alkali is added?

A

H+ + HCO3- ⇌ CO2 + H2O

Add OH- —> reacts with H+ to form H2O, then shifts equilibrium left to restore H+ lost
Add H+ —> equilibrium shifts to the right, removing excess H+

54
Q

What products are buffers found in?

A

Shampoos, detergents —> important to keep pH right to avoid damage to skin, hair,fabrics

A Level Physical Chemistry (12 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions