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a. Combustion-
Alkanes are relatively stable molecules, but heat or light will activate reactions that
involve the breaking of C–H and C–C single bonds.

Combustion is one such reaction:
- CH (g)+2O (g)⟶CO (g)+2H O(g)
4
2
2
2
- 2C H (g)+ 7O (g)⟶ 4CO (g)+ 6H O(g)
2
2
2
4 6

Alkanesundergo-
 complete combustion,
 burn with a blue flame,
 Have a high calorific value.
Hence they are often used as fuels.

Example- Combustion of LPG-
In the presence of sufficient oxygen, LPG burns to form water vapour and carbon
dioxide, as well as heat.
If enough oxygen is not present
for completecombustion of LPG, incompletecombustion occurs with water,
carbon,carbon dioxide&carbon monoxide being produced.
Chemical equation-
- complete combustion 2C H (g)+ 7O (g)⟶ 4CO (g)+ 6H O(g)
2
2
2
4 6
- incomplete combustion 2C H (g)+ 7O (g)⟶ 8CO(g)+ 6H O(g)
2
2
4 6

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