General Formula🤨
The alkanes are a family of hydrocarbons that share the same general formula.
This is: CnH2n+2
The general formula means that the number of hydrogen atoms in an alkane is double the number of carbon atoms, plus two.
- For example, methane is CH4 and ethane is C2H6.
Alkane molecules can be represented by displayed formulae in which each atom is shown as its symbol (C or H) and the chemical bonds between them by a straight line. You will definitely have to know how to read and draw these formulas in the actual I/GCSE Chemistry exam.
Properties💪
Alkanes are saturated hydrocarbons. This means that their carbon atoms are joined to each other by single bonds. This makes them relatively unreactive, apart from their reaction with oxygen in the air, which we call burning or combustion.
Alkanes can be used as fuel. As the chain length of the alkane increases, it can be noted that the boiling point of the molecules increases.
- Physical properties: Alkanes are less dense than water.
- Chemical properties: Alkanes are combustible due to the fact that they have the hydrocarbon chain within the molecule.
This is the same for alcohols, but less energy is needed to separate the bonds in an alcohol, so the chemical reaction with oxygen in the air takes place more easily than it does for alkanes. Alkanes do not react with metals, acids or alkalines, because the C-C and C-H bonds are highly unreactive. Alcohols will react with sodium, less vigorously than sodium reacts with water.
References: http://www.tutormyself.com/wp-content/uploads/img_5573e0884dd7a.png
Drafted by Catrina (Chemistry)