C7 - Organic Chemistry

Question 1

What is the formula for an alkane?

Answer 1

C n H 2 n+2

Question 2

What does ‘saturated’ mean for alkanes?

Answer 2

It consists of only single bonds. C-C.

Question 3

Describe a homologous series.

Answer 3

Organic compounds that react in a similar way.

Question 4

Name the first 4 alkanes.

Answer 4

1. Methane
2. Ethane
3. Propane
4. Butane

Question 5

Why does viscosity change for each hydrocarbon?

Answer 5

The shorter it is, the less viscous (gloopy) it is.

Question 6

What length hydrocarbons are more volatile?

Answer 6

Shorter hydrocarbons are more volatile.

Question 7

Why does the flammability change for each hydrocarbon?

Answer 7

The shorter it is, the more flammable (easy to ignite) it is.

Question 8

When will complete combustion happen?

Answer 8

When there is enough oxygen

Question 9

Give the word equation for incomplete combustion.

Answer 9

hydrocarbon + oxygen → carbon dioxide + water (+ energy)

Question 10

What happens to hydrocarbons during complete combustion?

Answer 10

They oxidise.

Question 11

Why are hydrocarbons useful as fuels?

Answer 11

Because of the amount of energy they produce during complete combustion.

Question 12

How was crude oil formed?

Answer 12

Dead plants and animals (mainly plankton) became trapped in mud under a high temperature and pressure.

Question 13

Give 1 problem with Crude Oil.

Answer 13

It is a finite resource, non-renewable.

Question 14

What is crude oil?

Answer 14

A mixture of lots of different hydrocarbons.

Question 15

What is the first step of Fractional Distillation?

Answer 15

Crude oil is heated to around 450 degrees so it vaporises.

Question 16

What happens in fractional distillation after crude oil has been heated?

Answer 16

The gas enters a fractionating column, where there is a temperature gradient.

Question 17

How does the crude oil separate once in a column?

Answer 17

Long hydrocarbons have a high boiling point so cool and condense into liquids near the bottom of the column.

Opposite for short hydrocarbons.

Question 18

Give 2 uses of crude oil.

Answer 18

1. Fuel

2. Petrochemical industry (e.g. for polymers, solvents, lubricants)

Question 19

What is the goal of fractional distillation?

Answer 19

To separate crude oil into fractions.

Question 20

What is the goal of cracking?

Answer 20

To produce shorter, more useful alkanes and alkenes from longer hydrocarbons.

Question 21

How do you test for alkenes?

Answer 21

Put in bromine water and shake. If the orange bromine water becomes decolourised, an alkene is present.

Question 22

What type of reaction is cracking?

Answer 22

Thermal decomposition.

Question 23

Describe catalytic cracking in 3 steps.

Answer 23

1. Vaporise
2. Pass over hot powdered aluminium oxide catalyst.
3. Long-chain splits on surface of specks of catalyst.

Question 24

Describe steam cracking in 3 steps.

Answer 24

1. Vaporise
2. Mix with steam
3. Heat to a higher temp