Ch.9.3

Question 1

What is neutralisation?

Answer 1

The chemical reaction that is caused by the reaction of acids and alkalis when they are mixed together.

Question 2

Neutralisation can change the ___________________ or ___________________ of a solution. Therefore, ____________________________________________________________________________.

Answer 2

acidity, alkalinity, the pH value of the solution also changes

Question 3

Give one example of neutralisation in our daily lives.

Answer 3

A mild alkali is present in many shampoos to help remove grease, but it also causes the hair to become tangled.
Some hair conditioners contain a mild acid which can neutralise the mild alkali in the shampoos, making hair easier to comb.

Question 4

What are reactants?

Answer 4

They are the substances which take part in a chemical reaction.

Question 5

What are products?

Answer 5

They are the substances formed, as a result of a chemical reaction.

Question 6

In neutralisation, the ________________ and the ________________ are the reactants.

Answer 6

acid, alkali

Question 7

How can we separate the salt that is formed in neutralisation from the rest of the solution?

Answer 7

When we evaporate the neutralised solution to dryness, a white solid is left on the watch glass. The white solid is a salt.

Question 8

What are the products of neutralisation?

Answer 8

Salt and water.

Question 9

What does the rise in temperature of a neutralised mixture mean?

Answer 9

It means that heat is released during neutralisation.

Question 10

Name the products of the formula sodium hydroxide + hydrochloride acid. What is the use of the salt formed?

Answer 10

water, heat, sodium chloride; it is used as table salt.

Question 11

Name the products of the formula potassium hydroxide + nitric acid. What is the use of the salt formed?

Answer 11

water, heat and potassium nitrate; it is used to make fertilisers.

Question 12

Name the products of the formula calcium hydroxide + sulphuric acid. What is the use of the salt formed?

Answer 12

water, heat and calcium sulphate; it is used to make tofu.

Question 13

What is the word equation of neutralisation?

Answer 13

acid + alkali ➞ salt + water

Question 14

__________________ is conserved in neutralisation.

Answer 14

Mass

Question 15

What are the five applications of neutralisation?
1.
2.
3.
4.
5.

Answer 15

1. Prevention of tooth decay
2. Relieving stomach upset
3. Treatment of insect stings and bites
4. Treatment of industrial waste containing acids or alkalis
5. Regulation of pH value of soil

Question 16

Explain how neutralisation can help with the prevention of tooth decay.
problem:
solution 1:
solution 2:
conclusion:

Answer 16

—There are a lot of bacteria in our mouths — they convert sugar left in food residue into acids. These acids attack the teeth and eventually cause tooth decay.
—Toothpaste is slightly alkaline and brushing teeth with toothpaste can neutralise the acids in the mouth.
—Chewing sugar-free gum after a meal can help prevent tooth decay. This is because chewing sugar-free gum can help stimulate the production of saliva in the mouth (saliva is slightly alkaline which can neutralise the acids in the mouth)
—Brushing teeth with toothpaste and chewing sugar-free gum can help neutralise the acids produced from bacterial action in our mouths.

Question 17

Explain how neutralisation can help with relieving stomach upset.
problem:
solution:

Answer 17

—Our stomachs produce hydrochloride acid to digest food. Sometimes our stomachs may produce too much acid and cause a burning sensation inside our stomachs.
—Antacids can be used to relieve stomach upset. Many antacids contain alkalis which can neutralise excess acid in stomachs.

Question 18

Explain how neutralisation can help with the treatment of insect stings and bites.
problem:
solution:
example 1:
example 2:

Answer 18

—Stings or bites of some insects may contain acidic or alkaline substances that cause the affected area to be itchy or painful.
—We can apply acidic or alkaline substances to the affected area to treat insect stings or bites.
—The stings of bees, ants and mosquitoes contain acids — these acids can be neutralised by alkalis (eg soap)
—The sting of a wasp contains alkalis — it can be neutralised by acids (eg vinegar)

Question 19

Explain how neutralisation can help with the treatment of industrial waste containing acids or alkalis.
problem:
solution:

Answer 19

—Industrial waste produced by factories of electroplating, dyeing, and electronic and chemical products often contain acids or alkalis. These acidic or alkaline wastes may cause serious water pollution if they are discharged without proper treatment
—To reduce pollution, alkalis (eg calcium hydroxide) are added to acidic wastes (or vice versa) to form precipitate before these wastes are discharged. The precipitate can be filtered out and removed. This can help reduce water pollution.

Question 20

Explain how neutralisation can help with the regulation of pH value of soil.
problem:
solution 1:
alternatives for solution 1:
solution 2:
alternatives for solution 2:

Answer 20

—Many plants do not grow well in soil which is too acid or too alkaline
—If the soil is too acidic, farmers will add slaked lime (calcium hydroxide) to the soil before growing crops. Slaked lime is an alkali which can neutralise acid in the soil.
—Sometimes powdered limestone (calcium carbonate) or lime (calcium oxide) is added instead of slaked lime.
—If the soil is too alkaline, farmers may add sulphur to the soil. Natural soil bacteria can convert sulphur in the soil to sulphuric acid, which can neutralise alkali in the soil
—To make the soil less alkaline, ammonium sulphate is commonly added too