Chemistry IGCSE CIE 0620 (2023 - 2025)

Question 1

What are the products of fermentation?

Answer 1

• Carbon dioxide
• Ethanol

Question 2

Which gas is used to convert iron into steel?

Answer 2

Oxygen

Question 3

What is the ore of Aluminium?

Answer 3

Bauxite (mainly constituent of aluminium oxide - Al₂O₃)

Question 4

What is the relative mass of an electron?

Answer 4

1/1840

Question 5

Describe the bonding in a metallic element. [3]

Answer 5

The bonding is known as metallic bonding. It consists of positive ions embedded in a sea of delocalised electrons. There is the presence of opposite charges creates an electrostatic attractive forces due to the positive charge of the ions and the negative charge of the delocalised electrons.

Question 6

Why do solid metals conduct electricity? [1]

Answer 6

Because they have free-moving OR mobile electrons.

Question 7

State the colour of methyl orange in 3 types of mediums: Acidic, Neutral, and Basic.

Answer 7

• Acidic: Red
• Neutral: Orange
• Basic: Yellow

Question 8

How do you decide when a suitable number of results have been obtained?

Answer 8

When at least 2 results are within 0.2 cm³ or less of each other.

Question 9

State the steps of the Contact process.

Answer 9

1. Molten sulfur burns in air to produce sulfur dioxide.
2. Sulfur dioxide reacts with oxygen to form sulfur trioxide (reversible reaction).
   ( 2SO₂ + O₂ ⇌ 2SO₃ )
3. Sulfur trioxide combines with concentrated sulfuric acid to form oleum (H₂S₂O₇)
   ( SO₃ + H₂SO₄ → H₂S₂O₇ )
4. Oleum reacts with water to form concentrated sulfuric acid.

Question 10

What is the name for the process of producing Sulfuric Acid?

Answer 10

Contact Process

Question 11

What are the conditions for the reaction between sulfur dioxide and oxygen to produce sulfur trioxide?

2SO₂ + O₂ ⇌ 2SO₃

Answer 11

• Temperature: 450°C
• Catalyst: Vanadium (V) oxide - V₂O
• Pressure: 1-2 atm (200kPa)

Question 12

What is the name of this compound: H₂S₂O₇?

Answer 12

Oleum

Question 13

State the characteristics of an equillibrium.

Answer 13

• Rates of forward and backward reactions are equal.
• Concentration of reactants and products are constant.

Question 14

What is the general formula of carboxylic acids?

Answer 14

CₙH₂ₙ₊₁COOH

Question 15

Name the ore of Zinc.

Answer 15

Zinc Blende (mainly ZnS - Zinc Sulfide)

Question 16

State the steps of the extraction of Zinc from its ore.

Answer 16

1. ZnS is roasted in air to be converted into Zinc Oxide.
2. Zinc oxide is reduced by Carbon/Carbon Monoxide in a furnace (Zinc produced is a gas).
3. Zinc gas is cooled to produce molten zinc.

Question 17

State the physical differences between Group I elements and transition elements.

Answer 17

• Group I elements have lower melting points.
• Group I elements have lower densities.
• Group I elements are less strong.
• Group I elements are softer.