Brainscape's Knowledge GenomeTM

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


See full index

Chemistry A Level > Topic 18 - Acids and Bases > Flashcards

Topic 18 - Acids and Bases Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Chemistry flashcards Periodic Table flashcards Chemistry 101 flashcards Organic Chemistry 101 flashcards
1
Q

Defintion of Bronsted Lowry acid

A

Proton donor
(Donates H+ ions)

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

Defintion of Bronsted Lowry base

A

Proton acceptor

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

Equation when strong acid is added to water

A

HA(aq) + H2O(l) –> H3O+ (aq) + A-

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

Equation for when base is added to water

A

B(aq) + H2O <—> BH+(aq) + OH-(aq)

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

Defintion of monoprotic acid

A

Acid that releases one H+ ion per molecule

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

Definintion of diprotic acid

A

Acid that realeases two H+ ions per molecule

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

Why is the logarithmic scale used for PH values?

A

The concentration of hydrogen ions can vary widely so alog scale is used. A minus sign is used to get rid of negative values.

The smaller the pH, the greater the concentration of H+

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

Equation for calculating H+ from pH

A

[H+] = 10^-pH

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

Equation for calculating the pH of strong acids

A

pH = -log [H+]

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

Value for Kw of an aqueous solution at a given temp

A

1.00x10^14 mol2dm-6

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

Defintion of neutral

A

[H+] = [OH-]

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

Things you need to know for calculating the pH of strong bases

A
  • Strong bases fully ionise in water.
  • They donate one mole OH- per mole of base
  • The concentration of OH- ions is the same as the concentration of the base
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Steps for calculating the pH of an alkaline solution

A
  1. Find the calues of Kw and [OH-]
  2. Rearrange the equation, substitute the values for Kw and [OH-] into the equation and solve it to find [H+]
  3. Put the [H+] into the pH equation
    pH = log10 [H+]
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Things you need to know calcualting the pH of weak acids - Ka

A

Only a small number of the molecules break aprt to form ions
HX <—> H+ + X-
For a weak aqueous solution acid, HA:
HA(aq) <–> H+(aq) + A-(aq)

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

For a weak acid the symbol Ka is used and is called the acid dissaoction constant

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

When dealing with weak acids you can assume that all the [H+] = [A-]

So the simplified version is:

Ka = [H+]2 / [HA]

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

Solution of a weak acid in water with nothing else added

A

[H+] = [A-]

[HA] ~ [HA] initial

The concentration of HA at equilibrium is virtually the same as it was before any o fit dissociated as so little dissociates

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

Steps for finding the pH of weak acids

A
  1. Write the expression for Ka for the weak acid
  2. Rearrange the equation and substitute in the values you know to find [H+]^2
  3. Take the square root to find [H+]
  4. Substitute [H+] into the pH equation to find the pH
17
Q

Steps for finding the concentration of weak acid

A
  1. Substitute the pH into the inverse pH equation to calculate [H+]
  2. Write an expression for Ka
  3. Rearrange equation and substitue the values for ka and [H+] into the equation and solve
18
Q

Use and formula of pKa

A

The value of Ka massively varies from one acid to the next. This can make numbers difficult to convert/ manage so pKa can be used.

pKa= -log10(Ka)

19
Q

Steps of calculating the pH of mixtures

A
  1. Write a balanced equation
  2. Calculate moles of H+
  3. Calculate moles of OH-
  4. Calculate moles in xs either H+ or OH-
  5. Calculate pH
20
Q

Things need to know for calculating mixtures of weak acids and strong bases

A

When a weak acid reacts with a strong base, for every mole of OH- added, one moles of HA is used up and one mole of A- is formed.

21
Q

Calculating mixtures of weak acids and strong bases
- If XS HA

A
  1. Calculate moles of HA
  2. Calculate the moles of OH-
  3. Calculate moles XS HA or OH-
  4. Calculate moles HA left and A- formed
  5. Calculate [HA] leftover and [A-] formed
  6. Use Ka to find [H+]
  7. Find pH
22
Q

Calculating mixtures of weak acids and strong bases
- If XS OH-

A
  1. Calculate moles of HA
  2. Calculate the moles of OH-
  3. Calculate moles XS HA or OH-
  4. Calculate [OH-]
  5. Use Kw to find [H+]
  6. Find pH
23
Q

Calculating mixtures of weak acids and strong bases
If mole HA = OH-

A
  1. Calculate moles of HA
  2. Calculate the moles of OH-
  3. Calculate moles XS HA or OH-
  4. pH = pKa of weak acid
24
Q

Vertical point and indicator of Strong acid and Strong base

A

pH 3-10
Phenolphthalein

25
Q

Vertical point and indicator of Strong acid and weak base

A

pH 3-8
Phenolphthalein

26
Q

Suitable indicatior weak acid and strong base

A

Methyl orange

27
Q

Vertical point and indicator of weak acid and weak base

A

No vertical point so no indicator used

28
Q

Uses of buffers in everyday life

A

Shampoo
Biological washing powder

29
Q

Indicator colours acid to base and PH range

A

Methyl orange- Red to yellow 3.2 to 4.4
Phenolphthalein- Colourless to pink 8.2 to 10.0

30
Q

Equations to show action of buffer

A

Addition of acid: CH3COO- + H+ —–> CH3COOH
Addition of base: CH3COOH + OH- —–> CH3COO- + H2O

31
Q

Meaning of the term buffer solution

A

A solution which resists/ minimises change in PH when small amounts of acid/ alkali added

32
Q

Use equations to show how blood resists changes in PH

A

Chemistry A Level (30 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions