Acids and Bases

Question 1

Amphoteric and example

Answer 1

Can act as either an acid or a base.
Eg. Water

Question 2

Dissociation constant for water

Answer 2

Kw, ionic product.

Question 3

Dissociation constant, Kw equation

Answer 3

Kw = [H30+][OH-]

Question 4

Kw value at 25°C

Answer 4

1*10^-14

Question 5

Relationship between pH and hydrogen ion concentration

Answer 5

pH=-log10[H30+]
[H30+] = 10^-pH

Question 6

Brønsted-Lowry definition of acids and bases

Answer 6

Acid is a proton donator and base is a proton acceptor.

Question 7

For every acid there is a….

Answer 7

Conjugate base formed when a proton lost.

Question 8

For every base there is a ….

Answer 8

Conjugate acid formed when a proton is gained

Question 9

What do strong acids and bases do in solution?

Answer 9

Completely dissociate into ions.

Question 10

What do weak acids do in solution?

Answer 10

Partially dissociate into ions.

Question 11

Strong acid examples

Answer 11

Hydrochloric, sulfuric and nitric acid.

Question 12

Weak acid examples

Answer 12

Ethanoic, carbonic and sulforous acid.

Question 13

Strong base examples

Answer 13

Metal hydroxides.

Question 14

Weak base examples

Answer 14

Ammonia and amines.

Question 15

Similarities and differences between weak and strong acids/bases

Answer 15

Differences - pH, conductivity and reaction rates.
Similarities - Stoichiometry e.g. in titration weak bases neutralises strong acid.

Question 16

Approx pH of weak acid equation

Answer 16

pH=1/2pKa-1/2log10c

Question 17

Salt pH explanation

Answer 17

Draw out equilibrium equation of water and draw out dissociation equation of salt. Each of the dissociated salt ions will react with the water ions. Weak one will form equilibrium but strong will not as once it turns into strong acid or base it will immediately dissociate. Since the weak acid or alkali has set up an equilibrium it is removing hydroxide or hydrogen ions from the equilibrium and adding water to it. Subsequently shifting water equilibrium to the right producing more base or acid.

Question 18

Buffer solution definition

Answer 18

A solution that remains relatively constant pH despite small amounts of acids, bases or water being added.

Question 19

What does an acid buffer solution consist of?

Answer 19

A weak acid and one of its salts made from a strong base

Question 20

What does a basic buffer solution consist of?

Answer 20

A weak base and a salt of its base made from a strong acid.

Question 21

How does an acidic buffer solution work?

Answer 21

Weak acid will provide hydrogen ions when these are removed by the addition of a small amount of base. The salt will provide the conjugate base which can absorb the excess hydrogen ions produced by the addition of a small amount of acid.

Question 22

How does a basic buffer solution work?

Answer 22

Weak base removes excess hydrogen ions and conjugate acid provided by the salt supplies the hydrogen ions when these are removed.

Question 23

Approx buffer pH equation

Answer 23

pH=pKa -log10(acid/salt)

Question 24

Indicators are ..

Answer 24

Weak acids

Question 25

Indicator dissociation equation

Answer 25

HIn(aq) + H2O(l) <=> H30+(aq) + In-(aq)

Question 26

How is the colour of an indicator determined?

Answer 26

By the ratio of HIn to In-

Question 27

pH range over which a colour change occurs can be estimated by the equation

Answer 27

pH = pKin +-1