Organic Chemistry - Fuels

Objective: State that hydrocarbons are compounds that contain hydrogen and carbon only

What are Hydrocarbons?

Hydrocarbons are a class of organic compounds. The defining characteristic of hydrocarbons is their chemical composition: they are composed of only hydrogen (H) and carbon (C) atoms.

Types of Hydrocarbons

Hydrocarbons are broadly classified into three main types:

• Alkanes: Saturated hydrocarbons where all carbon-carbon bonds are single bonds.
• Alkenes: Unsaturated hydrocarbons containing at least one carbon-carbon double bond.
• Alkynes: Unsaturated hydrocarbons containing at least one carbon-carbon triple bond.

Examples of Fuels

Many fuels are hydrocarbons. The type of hydrocarbon influences the fuel's properties and how efficiently it burns.

Table: Properties of Common Fuels

Fuel	Chemical Formula	Type of Hydrocarbon	Energy Content (kJ/g)	Advantages	Disadvantages
Petrol (Gasoline)	C$_8$H$_18$ (mixture of isomers)	Alkane	44.7	High energy density, readily available	Pollution (unburnt hydrocarbons)
Diesel	C$_12$H$_26$ (mixture of isomers)	Alkane	45.2	High energy density, efficient engine power	More pollution than petrol (particulates)
Natural Gas	Methane (CH$_4$)	Alkane	55.5	Clean burning (relatively), readily available	Can leak, potential for explosions
Coal	Complex mixture of hydrocarbons	Complex mixture (primarily hydrocarbons)	30.4	Abundant, relatively inexpensive	High pollution (soot, greenhouse gases)

Key takeaway: Understanding that fuels are often hydrocarbons is fundamental to understanding their properties and environmental impact.