C1.4 Crude oils and fuels

Question 1

crude oil

Answer 1

mixture of hydrocarbons found in the earth

Question 2

alkanes

Answer 2

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 burning or combustion, which is their reaction with oxygen in the air.
CnH2n+2

Question 3

Distillation

Answer 3

Distillation is a process that can be used to separate a pure liquid from a mixture of liquids. It works when the liquids have different boiling points. Distillation is commonly used to separate ethanol (the alcohol in alcoholic drinks) from water.
heating → evaporating → cooling → condensing

Question 4

Fractinal distillation

Answer 4

Some / most of the hydrocarbons (or petrol) evaporate / form vapours or gases
 When some of / a fraction of the hydrocarbons (or petrol) cool to their boiling point they
condense
 Hydrocarbons (or petrol) that have (relatively) low boiling points and are collected near
the top of the fractionating column or hydrocarbons with (relatively) high boiling points
are collected near the bottom of the fractionating column
 The process is fractional distillation
 Heat the crude oil / mixture of hydrocarbons or crude oil / mixture is heated to about
350°C
 Some of the hydrocarbons remain as liquids
 Liquids flow to the bottom of the fractionating column
 Vapours / gases rise up the fractionating column
 Vapours / gases cool as they rise up the fractionating column
 The condensed fraction (or petrol) separates from the vapours / gases and flows out
through a pipe
 Some of the hydrocarbons remain as vapours / gases
 Some vapours / gases rise out of the top of the fractionating column
 There is a temperature gradient in the fractionating column or the fractionating column is
cool at the top and hot at the bottom

Question 5

Combustion

Answer 5

combustion of hydrocarbon fuels releases energy
it need oxygen (oxidation)
Ethane+oxygen= C02 +water

Question 6

As you go up the fractionating column, the hydrocarbons have:

Answer 6

lower boiling points have :
lower viscosity (they flow more easily)
higher flammability (they ignite more easily).

Question 7

Explain the process of cracking

Answer 7

It is when long chain hydrocarbons ae broken down into smaller more useful molecules.
1===long chain fraction is heated and vapourised
2==vapours pass over a catalyst
3===products are short chains

Question 8

advantages of biodiesal

Answer 8

===renewable
===carbon neutral :plants absorb C02 as they grow
==biodegradable

Question 9

disadvantages of biodiesal

Answer 9

==large areas of land needed to ggrow fuel crops
===deforestation to plant fuel crops
burning biofuels releases more nitrogen oxide

Question 10

Incomplete combustion

Answer 10

If the oxygen supply is restricted - meaning that there’s not enough air - then the combustion of alkanes produces the poisonous gas carbon monoxide. For example, this equation shows the incomplete combustion of methane:
2CH4(g) + 3O2(g) → 2CO(g)+ 4H2O(g)

(Methane + Oxygen → Carbon monoxide + Water)