Summary
A homologous series is a group of organic compounds with similar chemical properties due to the same functional group, differing by a -CH2- unit. They show trends in physical properties and have general formulas, such as alkanes (CnH2n+2) and alkenes (CnH2n).
- Alkane — saturated hydrocarbons with single C-C bonds. Example: Methane (CH4)
- Alkene — unsaturated hydrocarbons with at least one C=C double bond. Example: Ethene (C2H4)
- Alcohol — organic compounds with an -OH functional group. Example: Ethanol (C2H5OH)
- Carboxylic acid — organic acids with a -COOH functional group. Example: Ethanoic acid (CH3COOH)
Exam Tips
Key Definitions to Remember
- Homologous series: A family of compounds with the same functional group and similar chemical properties.
- Saturated compound: Contains only single carbon-carbon bonds.
- Unsaturated compound: Contains one or more carbon-carbon double bonds.
Common Confusions
- Confusing the general formulas of alkanes and alkenes.
- Misunderstanding the difference between saturated and unsaturated compounds.
Typical Exam Questions
- What is the general formula for alkanes? CnH2n+2
- How do alkenes react with bromine water? They decolourise it from orange to colourless.
- What is a homologous series? A group of compounds with the same functional group and similar properties.
What Examiners Usually Test
- Understanding of general formulas for different homologous series.
- Ability to identify functional groups in organic compounds.
- Knowledge of reactions involving alkenes and bromine water.