Chapter 20 - Acids, Bases and pH

Question 1

What is the Bronsted-Lowry definition of an acid

Answer 1

• Proton donors
• When acids are dissolved in water, H+ ions are released

Question 2

What happens to H+ ions in water?

Answer 2

• They don’t exist on their own in water
• They form hydroxonium ions (H3O^+)
• Hydoxonium ions are what make a solution acidic

Question 3

What is the Bronsted-Lowry definition of a base?

Answer 3

• Proton acceptors
• When dissolved in water, they react to form OH- ions

Question 4

What are polyprotic acids?

Answer 4

• Some acids donate more than one proton (polyprotic) or polybasic

Question 5

Is Nitric Acid Polyprotic?

Answer 5

HNO3 is monoprotic

Question 6

Is sulphuric acid polyprotic?

Answer 6

H2SO4 is diprotic

Question 7

Is phosphoric acid polyprotic

Answer 7

H3PO4 is triprotic

Question 8

What is a neutralisation reaction

Answer 8

When an acid reacts with a base to produce a salt which is pH neutral

Question 9

How does Ammonia react with water to produce Hydroxide ions?

Answer 9

Accepts a proton to produce an Ammonium ion and hyrdoxide ion.

NH3 + H2O –> NH4+ + OH-

Question 10

How does Ammonia react with acids

Answer 10

to produce an ammonium salt (no water)

Question 11

Metal and acid

Answer 11

Salt and hydrogen

Question 12

Metal oxide and acid

Answer 12

salt and water

Question 13

metal hydroxide and acid

Answer 13

salt and water

Question 14

Metal carbonate and acid

Answer 14

salt, carbon dioxide and water

Question 15

What are conjugate acids and conjugate bases

Answer 15

• A conjugate acid has GAINED the proton
• A conjugate base has LOST the proton

Question 16

What is a strong base/acid

Answer 16

dissociate with ions completely

Question 17

What is a weak base/acid

Answer 17

partially dissociate when dissolved in water

Question 18

Examples of weak acid

Answer 18

• organic acids
• equilibrium lies to the left, backwards reaction favoured strongly

Question 19

Examples of weak bases

Answer 19

• Ammonia
• Backwards reaction favoured heavily

Question 20

How does water behave as a base in the presence of acid

Answer 20

accepts a proton to form a hydroxonium ion (H3O^+)

Question 21

How does water exist

Answer 21

it exists in equilibrium with its ions

Question 22

Equation for ionic product of water Kw

Answer 22

Question 23

is Kw a constant

Answer 23

The value of kw is the same in a solution for a given temperature

Question 23

What is the equation for finding pH

Answer 23

Question 24

Assumptions made to simplify Kw equation

Answer 24

• Pure Water has same concentration as OH- and H+ ions
  so for pure water Kw = [H+]^2

Question 25

Calculating the pH of a strong diprotic acid when given the concentration of the acid

Answer 25

• produces 2 H+ ions for every molecule of acid
• [H+] is 2x the concentration of the acid

Question 26

How to work out pH of a strong acid

Answer 26

Use Kw expression to find out [H+]

Question 27

Why is it harder to calculate the pH of weak acids

Answer 27

because they do not dissociate fully

Question 28

How to calculate the pH of a weak acid? What are the assumptions made?

Answer 28

By using Ka equation bellow.

Question 29

What is pKa? do strong acids have low or high pKa?

Answer 29

It is another way of measuring the strength of an acid
- the lower the value, the stronger the acid