Alkanes-Petroleum

Question 1

Fractional distillation

Answer 1

• Crude oil = vapourised at 350
• vapourised crude oil goes into the bottom of fractionating column, rises up through the trays
• largest hydrocarbons don’t vapourised : their boiling points are high, run to bottom- form gooey residue
• crude oil vapours goes up fractionating column as it goes up it gets cooler: creates a temperature gradient
• boiling points of alkanes increase as molecule gets bigger: each fraction condenses at different temps. Fractions are drawn off at different levels in the column.
• Hydrocarbons with lowest boiling points don’t condense, drawn off as gases at the top of the column.

Question 2

Fraction–Carbon chain–Uses

Answer 2

Gases–C1-C4–bottled fuels for camping
Petrol(gasoline)–C5-C12–fuel for cars
Naphtha–C7-C14–petrochemicals
Kerosene–C11-15–Jet fuel
Gas oil(diesel)–C15-19–central heating fuel
Mineral oil–C20-C30–Lubrication
Fuel oil–C30-C40–Power stations or ships
Wax–C40-C50–candles
Bitumen–C50+–road surfacing

Question 3

What is Petroleum?

Answer 3

Petroleum is a mixture consisting mainly of alkane hydrocarbons that can be separated by fractional distillation.