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Physical Chemistry Year 2 > Acids And Bases > Flashcards

Acids And Bases Flashcards

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1
Q

Define a Brønsted-Lowry acid

A

Proton donor

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2
Q

Define a Brønsted-Lowry base

A

Protons acceptor

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3
Q

What ion causes a solution to be acidic

Name and formula

A

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

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4
Q

What ion causes a solution to be alkaline

A

-OH

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5
Q

Write an equation for the ionisation of water

A

2H2O H3O+ + -OH

H2O H+ + -OH

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6
Q

Derive Kw using the equation for the ionisation is water

A

Kc = [H+] [OH-]
[H2O]

As [H2O] is so large compared to the other concentrations the concentration can be considered to be constant

Kw = [H+] [ OH-]

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7
Q

What is the value of Kw at 298K

A

1 x 10^-14

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8
Q

What physical factors affect the value of Kw

How do the affect it

A

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

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9
Q

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

A

[H+] = [ OH-]

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10
Q

Give an expression for pH in terms of H+

A

pH = -log10[H+]

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11
Q

What is the relationship between pH and concentration of H+

A

Lower pH the higher the concentration of H+

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12
Q

Of two solutions have a pH different of 1 what is the difference in [H+]

A

X10

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13
Q

How do you find [H+] from pH

A

10^-pH

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14
Q

How do you find [OH-] from pH in standard conditions

A

Find [H+] use Kw to calculate [OH-]

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15
Q

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

A

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

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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+]

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17
Q

Define the term strong acid

A

One which fully dissociates in water

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18
Q

Define the term strong base

A

One which fully dissociates in water

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19
Q

What is the difference between concentrated and strong

A

Concentrated means many mil per dm3

Strong refers t amount of dissociation

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20
Q

What is a weak acid and a weak base

A

Weak acids and bases do not fully dissociate in water

They only partially dissociate into their ions

21
Q

Examples of strong acids

A

HCl
H2SO4
H3PO4

22
Q

Examples of strong bases

A

NaOH
CaCO3
Na2CO3

23
Q

Examples of weak acids

A

CH3COOH

Any organic acid

24
Q

Examples of weak bases

A

NH3

25
Q

What is Ka

A

Ka = [H+][A-]

[HA]

26
Q

How would you work out the pH of a weak acid

A

Use Ka

Then pH = -log[H+]

27
Q

What is a titration

A

The addition of an acid/base of known titration to a base/acid of unknown titration to determine the concentration
An indicator is used to show that neutralisation has occurred or a pH meter

28
Q

Describe titration curve for strong acid with a strong base

A

High
Gradually decrease
Quick decrease then levels off

29
Q

Titration for a strong acid with a weak base

A

pH of about 9
Slight decrease
Quick decrease
Levels off

30
Q

Titration curve for a weak acid with weak base

A 
Ph of about 9 
Slight decrease 
Slight increase 
Quick decrease 
Levels off
31
Q

Titration curve for a weak acid and strong base

A

High pH
Levels off
Quick decrease
Levels off

32
Q

Define equivalence point

A

The point at which the exact volume of base has been added to just neutralise the acid

33
Q

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

A

There is a large and rapid change in pH

34
Q

What is the end point

A

The boiling of acid or alkali added when the indicator changes colour
If the right indicator is chosen then the equivalence point = end point

35
Q

What are the properties of a good indicator

A

Sharp colour Change
End point list be the same as the equivalence point
Distinct colour change

36
Q

What indicator would you use for a strong acid base titration

A

Phenolphthalein

37
Q

What indicator would you use a strong acid weak base titration

A

Methyl orange

38
Q

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

A

Phenolphthalein

39
Q

What indicator would you use for a weak acid weak base titration

A

Neither methyl orange or phenolphthalein

40
Q

Methyl orange

A

Red in acid
Yellow in alkali
Changed at pH 4-5

41
Q

Phenolphthalein

A

Colourless in acid
Red in alkali
Changes at pH 9-10

42
Q

What is the half neutralisation point

A

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

43
Q

Define a buffer solution

A

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

44
Q

What do acidic buffer solutions contain in general

A

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

45
Q

Equation for an acidic buffer with added acid

A

A- + H+ -> HA

46
Q

Equation for acidic buffer with added alkali

A

HA + OH- -> H2O + A-

47
Q

What do basic buffer solutions contain in general terms

A

Weak base and soluble salt of that weak base

48
Q

How can you calculate the pH of buffer solutions

A

Ka of weak acid

pH = -log[H+]

49
Q

Which buffer system maintains blood pH

A

H+ + HCO3- CO2 + H2O

Physical Chemistry Year 2 (5 decks)

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