ORGANIC CHEMISTRY - CHEMISTRY

Define isomer

Molecules with the same molecular formula but different structures

Define hydrocarbons

Molecules that contain only hydrogen and carbon, and have all single bonds

Why are alkanes classified as hydrocarbons

They are chains of carbon atoms surrounded by hydrogen atoms. They contain only hydrogen and carbon

What is the general formula for alkanes

CnHn+1

Name the first 6 alkanes

Methane, ethane, propane, butane, pentane, hexane

Describe the process of fractional distillation of crude oil

1. The oil is heated until most of turns into gas. The gas then enters a fractionating column

2. In the column there is a temperature gradient (hot at the bottom, cool at the top)

3. When the substances reach a part of the column where the temperature is lower than their boiling point they condense.

4. The longer hydrocarbons have high boiling point, and condense at the bottom

5. The shorter hydrocarbons have lower boiling points, so they condense at the top

6. The crude oil has now been split into its fractions

What is the order of fractions from top to bottom

Refinery gases, gasoline, kerosene, diesel, fuel oil, bitumen

What properties do hydrocarbons have as you go down the fractionating column

• their boiling points get higher

• Their length gets longer

• They get more viscous

• They get darker

Uses of refinery gases

Domestic heating and cooking

Uses of gasoline

Fuel in cars

Uses of kerosene

Fuel for planes

Uses of diesel

Fuel for trains and lorries

Uses of fuel oil

Fuel for large ships and power stations

Uses of bitumen

Surface roads and roofs

How is acid rain caused by burning hydrocarbons

• the fuels obtained from the hydrocarbons are burnt

• There are some sulfur impurities present in the hydrocarbon fuels

• When these impurities are burnt, sulfur dioxide is produced

• When sulfur dioxide mixes with water vapour, it produces dilute sulfuric cid

• This could lead to acid rain when these clouds fall

• The acid rain causes lakes to become acidic and kills plants/animals.