Acid Neutralisation

Question 1

What is a neutralisation reaction?

Answer 1

A reaction between an acid and a base.

Question 2

What is the pH scale used to do?

Answer 2

To classify substances as acidic, basic or neutral.

Question 3

What pH does a strong acid have? Give some common examples.

Answer 3

0 - 3.
Battery (sulphuric) acid: 0
Stomach acid: 0 - 1
Lemons (citric acid): 2
Grapes: 3
Vinegar (ethanoic acid): 3

Question 4

What pH does a weak acid have? Give some common examples.

Answer 4

3 - 7.
Tomatoes: 4
Bananas: 5
Milk: 6

Question 5

What is the neutral pH? Give some common examples.

Answer 5

7.
Pure water.
[NB: some substances that round to 7 can be considered neutral, e.g. which is often a very weak acid or base]

Question 6

What pH does a weak base have? Give some common examples.

Answer 6

7 - 11.
Eggs: 8
Baking soda: 9
Soap: 10

Question 7

What pH does a strong base have? Give some common examples.

Answer 7

11 - 14.
Bleach: 12
Oven cleaner: 13-14

Question 8

What are some common acids in the laboratory?

Answer 8

Sulphuric (0)
Nitric (1)
Hydrochloric (1 - 2)

Question 9

What are some common bases in the laboratory?

Answer 9

Ammonia (11 - 13)
Sodium hydroxide (14)

Question 10

What can be used to test whether a substance is acidic or basic? Give some examples.

Answer 10

An indicator — a chemical that is a different colour in acids and bases.
 — litmus paper
 — universal indicator 
 — methyl orange
 — phenolphthalein

Question 11

How does litmus paper work?

Answer 11

It either starts as red or blue. Either one will turn red in acids, blue in bases and purple in neutral solutions.

Question 12

How does universal indicator work?

Answer 12

Universal indicator paper/solution is a mixture of indicators; therefore, it can turn a range of colours in order to show the strength or weakness of the substance.
It gradually increases (red, orange, yellow, green, blue, purple) as the pH increases (i.e. red for strongest acid (0), green for purely neutral, purple for strongest base (14)).

Question 13

What will a reaction between an acid and a metal produce?

Answer 13

A salt and hydrogen.

Question 14

What will a reaction between an acid and a metal oxide produce?

Answer 14

A salt and water.

Question 15

What will a reaction between an acid and a metal hydroxide produce?

Answer 15

A salt and water.

Question 16

What will a reaction between an acid and a metal carbonate produce?

Answer 16

A salt, water and carbon dioxide.

Question 17

What is a salt?

Answer 17

A product of a neutralisation reaction. The hydrogen in the acid will have been replaced by the metal reactant to form said salt.

Question 18

What kind of salt will hydrochloric acid produce?

Answer 18

Chlorides.

Question 19

What kind of salt will sulfuric acid produce?

Answer 19

Sulfates.

Question 20

What kind of salt will nitric acid produce?

Answer 20

Nitrates.

Question 21

What happens when hydrochloric acid reacts with sodium hydroxide?

Answer 21

These substances will neutralise each other. Add some universal indicator to the HCl in the beaker. 23cm^3 of s.h. is originally added — steadily add more with a dropper. The solution will eventually turn green.
[NB: 1M (both): 25cm^3 HCl + ~25cm^3 sodium hydroxide.]

Question 22

What happens when sulfuric acid reacts with copper oxide?

Answer 22

Add the chemicals to a beaker. Stir for ~5 mins. The copper oxide will be in excess. The substances will neutralise e/o. Copper oxide is black, while copper sulfate is blue.
[NB: 25cm^3 2M sulfuric acid + 3g of copper (II) oxide.]

Question 23

What happens when sulphuric acid reacts with copper carbonate?

Answer 23

The chemicals are put in a conical flask/beaker. The green copper carbonate turns black and appears to ‘rise’ as CO2 is released. It will ‘fizz’ as well as changing colour.
[NB: 25cm^3 2M sulfuric acid + excess copper (II) carbonate.]

Question 24

What will putting charcoal in universal indicator do?

Answer 24

It will bind to the indicator; therefore, it cannot filter through filter paper.