Acid and Bases (1)

Question 1

What is PH?

Answer 1

• A measure of how Acidic or Alkaline a solution is
• A measure of the concentration of H+ ions in a solution

Question 2

What is the PH of water?

Answer 2

7

Question 3

Give two example of equipments that can be used to measure the PH

Answer 3

• PH indicator
• PH probe

Question 4

Give the colour change for PH from 0 to 14

Answer 4

Red - orange - yellow - green - blue - purple

Question 5

Advantages of using a PH probe compared to a PH indicator

Answer 5

• More accurate
• Does not involve guessing shades

Question 6

What is an acid?

Answer 6

Any substance that forms an aqueous solution with a PH less than 7
- Because they ionise in a aqueous solution, to release H+ ions

Question 7

What is a base?

Answer 7

Any substance with a PH greater than 7

Question 8

What is an alkali?

Answer 8

A base that dissolves in water to form a solution with a PH greater than 7.
Forming OH- (hydroxide ions) in water.

Question 9

What happens when an acid reacts with a base?

Answer 9

It forms a neutralisation reaction

Question 10

What does a neutralisation reaction produces?

Answer 10

Salt + water

Question 11

Give the formula for Hydrochloric acid

Answer 11

HCl

Question 12

Give the formula for Sulfuric acid

Answer 12

H2SO4

Question 13

Give the formula for Nitric acid

Answer 13

HNO3

Question 14

Give the formula for Sodium Hydroxide

Answer 14

NaOH

Question 15

Give the formula for Calcium Carbonate

Answer 15

CaCO3

Question 16

Define strong acids

Answer 16

An acid that ionises completely
All the particles will dissociate

Question 17

Define weak acid

Answer 17

Acids that do not fully ionise

Question 18

Why weak acids do not ionise fully?

Answer 18

Because they form a reversible reaction, which is in equilibrium.
And the equilibrium shifts to the left so there is far more molecules in the undissociated part.

Question 19

What is strength (in terms of acid)?

Answer 19

How much an acid dissociates

Question 20

What is concentration (in terms of acid)?

Answer 20

How much acid there is in a certain volume.
More concentrated solutions contain more acid per unit volume.

Question 21

What happens to the PH of a solution when the concentration of H+ ions gets higher?

Answer 21

The PH gets lower

Question 22

Why at any given concentration of strong acid, the solution will have a lower PH?

Answer 22

Because a higher proportion of the strong acid molecules will dissociate to release H+ ions

Question 23

Why do weak acids would need a really high concentration, to have a low PH?

Answer 23

Because few acid particles would ionise

Question 24

What is it formed when a Metal oxide or a Metal hydroxides reacts with an acid?

Answer 24

Salt + Water
(YOU TAKE THE -ve ION FROM THE ACID AND COMBINE IT WITH THE +ve ION FROM THE BASE)

Question 25

What is formed when a Metal carbonates reacts with an acid?

Answer 25

Salt + Water + Carbon dioxide

Question 26

How do make a soluble salt?

Answer 26

React an acid with an insoluble base

Question 27

Give the steps for the neutralisation process

Answer 27

- Place some dilute acid in a beaker - Gently heat it with a bunsen burner - Keep adding the insoluble base, a little bit at a time - As you add more, some of the base will no longer disappear (The base must be in excess now) - Now we neutralised all the acid - Filter out all of the excess of the base, using a filter funnel and a filter paper - What we have left is the dissolved form of the soluble salt

Question 28

How to get pure crystals of the soluble salt?

Answer 28

- Gently heat the filtered solution (using a water bath) - Which will evaporate off some of the water - Once we evaporated a bit of the water off and we started to see crystals forming, we stop heating it and leave it to cool, which will cause even more crystals to form -Filter the solution using a filter paper and a filter funnel - Dry out the crystals