Bases And Alkalis (T4)

Question 1

What is the pH of alkaline solutions?

Answer 1

More than 7

Question 2

What affect does the strength of the alkali have on the pH of a solution?

Answer 2

The stronger the alkali the higher the pH number

Question 3

What are bases and alkalis.

Answer 3

Bases are substances that can react with acids and neutralise them to make a salt and water.

Bases that dissolve in water are called alkalis.

Question 4

What form do bases and alkalis usually take?

Answer 4

They are usually metal oxides or metal hydroxides.

Question 5

Why is copper oxide not an alkali?

Answer 5

Because it does not dissolve in water.

Question 6

Why is sodium hydroxide an alkali?

Answer 6

Because it does dissolve in water. It is a base AND an alkali.

Question 7

What do alkalis do to red litmus paper?

Answer 7

The turn red litmus paper blue.

Question 8

What colour do alkalis turn universal indicator?

Answer 8

Dark blue or purple if they are strong, blue-green if they are weak.

Question 9

Whilst acids need hydrogen ions, alkali need…..

Answer 9

Hydroxide ions (OH-)

Question 10

All alkalis are ……. but only soluble bases are ……..

Answer 10

All alkalis are bases but only soluble bases are alkalis

Question 11

What is a common alkali used in the school laboratory?

Answer 11

Sodium hydroxide solution

Question 12

List some instances where bases and alkalis are found and used at home…

Answer 12

• bases react with oils and fats, so they are often used in strong household cleaners. For example, drain and oven cleaners usually contain sodium hydroxide
• ammonia is commonly used in cleaners and can be recognised by its choking smell
• weak bases and alkalis are found in toothpaste, antacid tablets and baking powder