3.1.12- Acids and Bases

Question 1

What is a brønsted Lowry acid

Answer 1

Proton donor

Question 2

What is brønsted Lowry base

Answer 2

Proton acceptor

Question 3

What is a brønsted Lowry reaction

Answer 3

Reaction involving the transfer of a proton

Question 4

What is a monoprotic acid

Answer 4

Acid that released one H+ ion per molecule

Eg HCl,HNO3

Question 5

What is a diprotic acid

Answer 5

Acid that release two H+ ions per molecule

Eg H2SO4

Question 6

Definition of ph

Answer 6

PH = -log(H+)

[H+] = 10^-pH

Question 7

What is Kw

Answer 7

Kw=[H+][OH-]

Question 8

What is Kw value

Answer 8

1.00x10-14

Question 9

Effect of temperature on Kw

Answer 9

As temperature increases the equilibrium moves right to oppose increase in temperature
So [H+] and [OH-] increases
Kw increases and pH decreases

Question 10

How to find ph of strong bases

Answer 10

[H+] = Kw/ [OH-]

Question 11

Find ph of mixture of strong acid and strong based

Excess H+

Answer 11

Mol H+ 
Mol OH- 
Xs mol H+ 
Xs [H+] =n/v 
pH= -log[H+]

Question 12

Find ph of mixture of strong acid and strong based

Excess OH-

Answer 12

Mol H+ 
Mol OH- 
Xs mol OH- 
Xs [OH-] = n/v 
[H+] = Kw/[OH-] 
-log[H+]

Question 13

What is a weak acid or base

Answer 13

Only partially dissociated

Question 14

Acid dissociation constant

Answer 14

Ka= [H+][A-]
—————
[HA]

pKa=-logKa

Ka= 10^-pKa

Question 15

What does a bigger value of Ka mean or smaller value of pKa mean

Answer 15

A strong acid

Question 16

Find pH of weak acid

Answer 16

Ka=[H+]^2
———
[HA]

pH=-log[H+]

Question 17

Reactions of weak acids

XS HA

Answer 17

1) mol of OH- left and A- formed
2) [HA] left over [A-] left
3) use Ka to find [H+]
4) find pH

Question 18

Reactions of weak acid

Xs OH-

Answer 18

1) [OH-]
2) Kw to find [H+]
3) find pH

Question 19

Reactions of weak acids when mol HA =OH-

Answer 19

pH= pKa of weak acid

Question 20

What is an indicator

Answer 20

Weak acids were HA and A- are different colours
Low pH HA present more
High pH A- present more

Question 21

What is methyl orange

Answer 21

When Red more HA
When yellow more A-
Changes at 3.2-4.4

Question 22

What is phenolphthalein

Answer 22

More HA is colourless
More A- is pink
Changed between 8.2-10.0

Question 23

What does equivalence point show

Answer 23

Where moles of alkali = moles of base

Question 24

What is an end point

Answer 24

Where the indicator changes colour

Question 25

Show what ph graph with weak acid base and strong acid base

Answer 25

Draw

Question 26

How to calculate pH of buffer when acid added

Answer 26

``` A-+H+ —-> HA Mol H+ added Work out [HA] and [A-] left Ka= [H+][OH-] —————- [HA] -log[H+] ```

Question 27

How to calculate pH of buffer when base added

Answer 27

Mol OH- HA+ OH- —> A- + H2O [HA] and [A-] Ka = [H+] [A-] ———— [HA] pH = -log[H+]

Question 28

What do buffer depend on

Answer 28

Ratio of HA to A- when small amount of acid or alkali added this does not change very much

Question 29

What is an acid buffer made from

Answer 29

Weak acid and salt of weak acid

Question 30

What is base buffer made out of

Answer 30

Weak base and salt of weak base