Unit 1: Chapter 4 - Crude Oils And Fuels

Question 1

Fuels from crude oils

What is Crude Oil?

What are fractions?

What are hydrocarbons?

What are saturated hydrocarbons?

What is the formula for saturated hydrocarbons?

Answer 1

CRUDE OIL is a mixture of lots of different chemical compounds.

It is not useful as there are too many substances within it with many different boiling points.

We must separate these properties of substances into FRACTIONS. We can separate mixtures through DISTILLATION, which separates liquids with different boiling points.

HYDROCARBONS

Nearly all compounds in crude oil are compounds containing only HYDROGEN and CARBON, hence the name hydrocarbons.

Methane (CH4)
Ethane (C2H6)
Propane (C3H8)
Butane (C4H10) and so on…

SATURATED hydrocarbons i.e ALKANES have a general formula:

CnH(2n+2) NOTE: n is any term for any number

SATURATED: Each molecules contains as much hydrogen atoms as possible. No more hydrogen can be added.

Question 2

Fractional Distillation

What are the different properties of both small and big hydrocarbons?

What is FRACTIONAL DISTILLATION?
How does it work?

Answer 2

The size of a hydrocarbon can vary. This also affects the properties of the hydrocarbon:

SMALL LARGE

LOW BOILING POINT HIGH
HIGH VOLATILITY LOW
RUNNY VISCOSITY THICK
VERY FLAMMABLE MINIMAL

FRACTIONAL DISTILLATION

We can separate crude oil through FRACTIONAL DISTILLATION. Each hydrocarbon has a different boiling point.

Firstly the oil is vaporized at 350C into a gas before going into the tower. The temperature is highest at the bottom of the tower and then slowly decreases as you go up the tower. Hydrocarbons with the lowest boiling points condense at its boiling point i.e at the top, whereas larger hydrocarbons with a higher boiling boiling condense at the bottom.

Temperature range: 40C to 340C

Question 3

Burning Fuels

Answer 3

Small hydrocarbons are much more useful as fuels as they release energy much quicker.

Gas + Oxygen -> water + carbon dioxide

The carbon and hydrogen are OXIDISED. Oxidised means adding oxygen in chemical reaction in which oxides are formed.

POLLUTION FROM FUELS

Fossil fuels produce CO2 and SO2 that may cause major problems, such as acid rain and global warming.

Also CO is formed when there is an INCOMPLETE COMBUSTION (lack of oxygen).

High temps cause nitrogen and oxygen to react together to form NO and are poisonous (trigger peoples’ asthma). Also cause acid rain.

Tiny solid carbon particulates are harmful when breathed in.

Question 4

Cleaner Fuels

Answer 4

CLEANING UP OUR ACT

We can reduce the effects of burning fuels by:

• Using CATALYTIC CONVERTERS (platinum). This greatly decreases the output of CO and NO produced in car engines.

CO + NO -> CO2 + N

These do not help lower the levels of CO2.

• Filters remove most particulates from modern diesel engines. The filters need to burn off trapped solid blocks so they do not get blocked.
• Sulfur dioxide is removed by reacting it with calcium oxide and or calcium hydroxide.
  Sulfur impurities can also be removed BEFORE being burned.

Question 5

Alternative Fuels

Answer 5

BIOFUELS

ADVANTAGES

• Less harmful to wildlife than diesel.
• Carbon-neutral
• Renewable

DISADVANTAGES

• Large areas for agriculture to produce fuel instead of food. May result in famine in poorer countries.
• Potential destruction of habitat
• Biofuels freeze before biodiesel and turns into sludge. May gum up engines at high temperatures.

ETHANOL AS A BIOFUEL

Created by fermenting sugar from sugar-based plants. Can be mixed with petrol to make ‘gasohol’. This would save money. It is also carbon-neutral.