Organic chemistry

Question 1

What two elements make up a hydrocarbon?

Answer 1

Hydrogen and Carbon

Question 2

Draw the structure of and write the formula for methane

Answer 2

Methane, CH₄

Question 3

Draw the structure of and write the formula for ethane

Answer 3

Ethane, C₂H₆

Question 4

Draw the structure of and write the formula for propane

Answer 4

Propane, C₃H₈

Question 5

Draw the structure of and write the formula for butane

Answer 5

Butane, C₄H₁₀

Question 6

What is crude oil a mixture of?

Answer 6

Hydrocarbons

Question 7

What process is used to separate the hydrocarbons found in crude oil?

Answer 7

Fractional Distillation

Question 8

The ancient remains of plankton and other marine organisms is the origin of what finite resource?

Answer 8

Crude oil

Question 9

Name three useful fuels obtained from crude oil.

Answer 9

Any three from: petrol, diesel, kerosene, heavy fuel oil and liquefied petroleum gas

Question 10

What is the general formula for a homologous series of alkanes?

Answer 10

C_nH_2n+2

Question 11

Name two useful materials that can be made from crude oil by the petrochemical industry.

Answer 11

Any two from: solvents, lubricants, polymers, detergents.

Question 12

Explain how fractional distillation of crude oil works.

Answer 12

• Crude oil (a mixture of different length hydrocarbons) is heated.
• Different length fractions have different boiling points. When heated, the fractions evaporate and rise up the tower.
• The fractions cool down as they rise up the tower. When they reach their condensing point, they will condense, turn into a liquid and flow out of the tower.

Question 13

Write a balanced equation for the complete combustion of propane

Answer 13

C₃H₈ + 5 O₂ → 3 CO₂ + 4 H₂O

Question 14

Write a balanced equation for the complete combustion of ethane

Answer 14

2 C₂H₆ + 7 O₂ → 4 CO₂ + 6 H₂O

Question 15

What is the relationship between the length of a hydrocarbon and boiling point

Answer 15

The longer the hydrocarbon, the higher the boiling point

Question 16

What is the relationship between the length of a hydrocarbon and viscosity

Answer 16

The longer the hydrocarbon, the higher the viscosity

Question 17

What is the relationship between the length of a hydrocarbon and flammability

Answer 17

The longer the hydrocarbon, the lower the flammability

Question 18

Describe the conditions needed for catalytic cracking

Answer 18

Catalyst (Aluminium oxide) and high temperature

Question 19

Describe the conditions needed for: steam cracking

Answer 19

Steam and high temperature

Question 20

What type of reaction is shown by the equation below? CH₄ + 2 O₂ → CO₂ + 2 H₂O

Answer 20

Combustion

Question 21

What are the products of cracking?

Answer 21

Alkanes and Alkenes

Question 22

What are the products of complete combustion of a hydrocarbon?

Answer 22

carbon dioxide (CO₂) and water (H₂O)

Question 23

What is the test for an alkene?

Answer 23

Add bromine water and it turns from orange to colourless

Question 24

Which are more reactive? Alkanes or Alkenes?

Answer 24

Alkenes

Question 25

Complete the equation

C₈H₁₈ → C₄H₁₀ + _______

Answer 25

C₈H₁₈ → C₄H₁₀ + C₄H₈

Question 26

What process is shown by the equation

C₈H₁₈ → C₄H₁₀ + C₄H₈

Answer 26

Cracking

Question 27

Why is cracking useful for modern life?

Answer 27

Alkenes (that are made from cracking) are used to make polymers

Alkenes (that are made from cracking) are used as the starting material for the production of many chemicals

Cracking produces short hydrocarbons that makes useful fuels