Chapter 9: Acid & Bases

Question 1

Define acid

Answer 1

An acid is a substance that produces hydrogen ions when dissolved in aqueous solution

Question 2

What are the properties of acid

Answer 2

1) Have a sour taste
2) Turn blue litmus paper blue to red
3) Dissolved in water to conduct electricity

Question 3

What are the reactions of acids

Answer 3

1. Metal + Acid –> Salt + Hydrogen gas
2. Carbonate + Acid –> Salt + H20 + Carbon dioxide
3. Base + Acid –> Salt + Water

Question 4

Define bases

Answer 4

A base is any metal hydroxide or oxide that reacts with acid to form salt and water only

Question 5

Define alkali

Answer 5

An alkali is a substance that produces hydroxide ions when dissolved in water

Question 6

What are the properties of alkali

Answer 6

1) Slippery and have a bitter tatse
2) Turns red litmus paper to blue
3) Reacts with water to form salt and water only

Question 7

State the reactions of alkali

Answer 7

1) Ammonium salt + Alkali –> salt + water + ammonia
2) Acid + Alkali –> Salt + water

Question 8

How to measure pH

Answer 8

1) pH meter
2) pH sensor attached to data logger

Question 9

Define indicators

Answer 9

Indicators are substances that shows different colours in acidic and alkaline solutions

Question 10

Describe how to use indicators

Answer 10

1) Add a few drops of indicator to the solution to be tested
2) Compare the colour of the solution with the pH scale

Question 11

Why is it important to control the pH of the soil

Answer 11

It affects the development and growth of plants . It grows well in slightly acidic and neutral

Question 12

Why pH of the soil become unsuitable for plant growth

Answer 12

1) Environmental pollution (acid rain)
2) Too much fertiliser was added

Question 13

How to treat acidity in the soil

Answer 13

Add calcium hydroxide or calcium oxide. It neutralise the acid in the soil

Question 14

Name the oxides

Answer 14

Metallic: Ionic
- Basic oxide
- Amphoteric oxide (ZAP)

Non-metallic: Covalent
- Neutral oxide
- Acidic oxide

Question 15

What are the properties of the oxide

Metallic: Ionic
- Basic oxide
- Amphoteric oxide (ZAP)

Non-metallic: Covalent
- Neutral oxide
- Acidic oxide

Answer 15

Basic oxide
- Solids at room temperature
- May be soluble or insoluble in water
- React with acid to form salt and water only

Amphoteric oxide
- Reacts as both a base and an acid
- ZAP

Acidic oxide
- Gas at room temperatures
- Dissolves in water to form acids
- React with alkali to form salt and water only

Neutral oxide
- Insoluble in water
- Shows neither properties of acidic or basic properties
- CNO