Summary of the Properties and Uses of Hydrocarbons |
| Name |
Molecular Formula |
Molecular Mass |
Melting Point (oC) |
Boiling Point (oC) |
State (25oC, 101.3kPa) |
Density (liquid g cm-3, 20oC) |
Flashpoint (oC) |
Enthalpy of Combustion (kJ mol-1) |
Uses |
|---|
| methane |
CH4 |
16 |
-182 |
-162 |
gas |
|
|
-889 |
major component of natural gas (fuel) |
|
| ethane |
C2H6 |
30 |
-183 |
-88.6 |
gas |
|
|
<-1557 |
component of natural gas (fuel) |
|
| propane |
C3H8 |
44 |
-188 |
-42.1 |
gas |
|
|
-2217 |
component of liquefied petroleum gas (LPG), bottled gas (fuel) |
|
| butane |
C4H10 |
58 |
-138 |
-0.5 |
gas |
|
|
-2874 |
component of liquefied petroleum gas (LPG), cigarette lighters (fuel) |
|
| pentane |
C5H12 |
72 |
-130 |
36.1 |
liquid |
0.626 |
-49 |
-3536 |
component of petrol (fuel) |
|
| hexane |
C6H14 |
86 |
-95.3 |
68.7 |
liquid |
0.659 |
-22 |
-4190 |
component of petrol (fuel) |
|
| heptane |
C7H16 |
100 |
-90.6 |
98.4 |
liquid |
|
-4 |
-4847 |
component of petrol (fuel) |
|
| octane |
C8H18 |
114 |
-56.8 |
126 |
liquid |
|
|
-5506 |
major component of petrol (fuel) |
|
| nonane |
C9H20 |
128 |
|
|
|
|
|
|
component of petrol (fuel) |
|
| decane |
C10H22 |
142 |
-30 |
174 |
liquid |
0.730 |
|
|
component of petrol (fuel) |
|
| hexadecane |
C16H34 |
226 |
18.5 |
288 |
liquid |
0.775 |
|
|
component of diesel fuel & heating oil |
|
| eicosane |
C20H42 |
282 |
36 |
343 |
solid |
|
|
|
|
| |
Trends
- Alkanes are colourless
methane to butane are colourless gases
(propane and butane are easily condensed under pressure & are commonly sold as liquids)
alkanes containing 5 carbons up to about 19 are colourless liquids
(petrol & kerosene are mixtures of liquid alkanes, dye is added to the fluids for safety reasons)
alkanes with more than about 20 carbon atoms are colourless, waxy solids
(paraffin wax is a mixture of solid alkanes)
- Alkanes are less dense than water (alkanes will float on top of water)
density increases with increasing molecular mass
- Simple alkanes have low melting and boiling points.
Alkanes are non-polar so only weak intermolecular forces act between the alkane molecules
(Van der Waal's Forces/London Forces/Dispersion Forces/Weak Intermolecular Forces)
Melting and Boiling Points increase as the molecular mass increases
- Alkanes are insoluble in polar solvents like water
- Alkanes are relatively unreactive
(they will combust: commonly used as fuels since large amounts of energy are released, the longer the chain, the more bonds are broken, the greater the energy released)
(will undergo halogenation by substitution reaction in the presence of ultra-violet light)
- Alkanes with *flashpoints below room temperature (the components of petrol for example) should be stored in strong metal containers with narrow mouths & tightly sealed lids to prevent the vapour from escaping & to prevent a naked flame or spark from igniting the vapour/air mixture.
*Flashpoint: the minimum temperature at which the vapour pressure of a liquid is high enough for an explosive mixture to be formed with air. Safety precautions for handling & storing fuels are determined by the flashpoint.
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