Chemistry A2 - Acids, Buffers, and Bases

Question 1

What is a Bronsted acid?

Answer 1

A species which can donate a proton

Question 2

What is an example of a Bronsted aicd?

Answer 2

HCl

Question 3

What is a Bronsted base?

Answer 3

A species which can accept a proton

Question 4

What is an example of a Bronsted base?

Answer 4

A hydroxide ion (OH-)

Question 5

Define a weak acid

Answer 5

One which only partially dissociates in solution

Question 6

What is an example of a weak acid?

Answer 6

Ethanoic acid (CH3COOH)

Question 7

What are monobasic/monoprotic acids?

Answer 7

Acids which contain one ionisable hydrogen atom in each molecule, HCl, for example

Question 8

What are dibasic/diprotic acids?

Answer 8

Acids which contain two ionisable hydrogen atoms per molecule, H2SO4, for example

Question 9

What are tribasic/triprotic acids?

Answer 9

Acids which contain three ionisable hydrogen atoms per molecule, H3PO4, for example

Question 10

Acid + metal –> ?

Answer 10

Salt + hydrogen

Question 11

Acid + metal oxide –> ?

Answer 11

Salt + water

Question 12

Acid + metal carbonate –> ?

Answer 12

Salt + water + carbon dioxide

Question 13

Acid + alkali –> ?

Answer 13

Salt + water

Question 14

What is the overall expression for Ka?

Answer 14

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

Question 15

What can we tell about an acid if it has a higher Ka value?

Answer 15

It is a stronger acid - the higher the value, the more dissociated the acid and the stronger it is

Question 16

How do we calculate pKa?

Answer 16

-log(Ka)

Question 17

How do we calculate pH?

Answer 17

-log[H+]

Question 18

How do we calculate the concentration of H+ when we know the pH of the solution?

Answer 18

10^ -pH

Question 19

What is the equation for the ionic product of water (Kw)?

Answer 19

[H+][OH-]

Question 20

How do we find the Ka for a weak acid experimentally?

Answer 20

1. Prepare a standard solution of the weak acid of known concentration
2. Measure the pH of the standard solution using a pH meter
3. Do some calculations to find Ka

Question 21

What are two approximations we make when carrying out calculations which involve weak acids?

Answer 21

• The concentrations of H+ and A- are equal
• The dissociation of water is negligible

Question 22

What is the importance of Kw?

Answer 22

It sets up the value for the neutral point on the pH scale

Question 23

What is the [H+] and [OH-] in an acid solution with a pH of 3?

Answer 23

[H+] = 10^-3
[OH-] = 10^-11

Question 24

What is a buffer solution?

Answer 24

A solution which resists changes in pH when small amounts of acids or alkalis are added