Acids and bases

Question 1

Acid + Metal –>

Answer 1

Salt + Hydrogen

Question 2

Acid + Metal Oxide –>

Answer 2

Salt + Water

Question 3

Acid + Metal Hydroxide

Answer 3

Salt + Water

Question 4

Acid + Metal carbonate

Answer 4

Salt + CO2 + H2O

Question 5

Define an acid

Answer 5

Proton donor

Question 6

Define a base

Answer 6

proton acceptor

Question 7

What does amphoteric mean?

Answer 7

Water can act as either an acid or a base

Question 8

How to calculate pH

Answer 8

-log[H+]

Question 9

How to calculate [H+] using pH

Answer 9

10^-pH

Question 10

Key points for the pH scale

Answer 10

The smaller the pH, the greater the concentration of H+ ions. A differnce of 1 on the scale means a differnce in x10 of [H+]

Question 11

Define a strong acid

Answer 11

Fully dissociates

Question 12

What does Ka stand for

Answer 12

equilibrium constant in terms of acid dissoiation

Question 13

Ka equation

Answer 13

products over reactants

Question 14

What is the differnce between monoprotic, diprotic and triprotic

Answer 14

Te amount of [H+] ions it contains
x1
x2
x3

Question 15

Define a weak acid

Answer 15

Only partially dissociates

Question 16

Ka for weak acid

Answer 16

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

Question 17

What type of acid is a craboxyllic acid

Answer 17

weak

Question 18

H+ using Ka

Answer 18

(square root)Ka[HA]

Question 19

pKa equation

Answer 19

-log[KA]

Question 20

Ka using pKa

Answer 20

10^-pKa

Question 21

Kw expression

Answer 21

[H+][OH-]

Question 22

H+ using Kw

Answer 22

Square root of Kw

Question 23

PH changes with temperature

Answer 23

At temp higher than 298K, equilibrium shifts to the right in the endothermic direction to oppose change. [H+] increases. However does not mean it goes more acidic as [H+]=[OH]-

Question 24

Calculating pH

Question 25

State why calibrating a pH meter just before it is used improves the accuracy of the pH measurement

Answer 25

After storage, it will not provide the right reading

Question 26

describe how you would obtain the pH curve for the titration

Answer 26

measure pH of acid, add alkali, stir, measure pH after each addition- repeat until in excess

Question 27

suggest why the conc of NaOH in a solution slowly decreased when left open in air

Answer 27

Reacts with Co2 in the air

Question 28

Explain why the temp rise is less

Answer 28

same amount of Q distributed over a larger volume

Question 29

pH of magnesium hydroxide compared to calcium

Answer 29

lower- Mg is less soluble

Question 30

Draw the displayed formula of H2SO4

Question 31

explain why H2O is not shown in the Kw expression

Answer 31

[H2O] is constant

Question 32

suggest why the pH probe is washed with distilled water between each measurement

Answer 32

to reduce contamination

Question 33

explain why the volume of NaOH added between each pH is smaller as the end point is approached

Answer 33

to avoid missing endpoint

Question 34

suggest a suitable piece of apparatus that could be used to measure out the sodium hydroxide solution, explain why this apparatus is more suitable than a pipette

Answer 34

burette- can deliver variable volumes

Question 35

why would the end point of the graph is difficult to judge accurately

Answer 35

the change in pH is gradual, would change colour over a range of volumes

Question 36

a practical procedure to obtain data that a graph could be plotted from

Answer 36

place in a fixed volume of alkali in a flask or beaker. add acid in small portions from burette, stir and use pH meter to record pH after each decision

Question 36

suggest how the practical procedure could be refined

Answer 36

repeat with indicator- select the indicator that changes colour rapidly from pH 7 to 4