4E SciChem Organic Chemistry

Which petroleum fraction is used as a fuel for aircraft engines?

• diesel

• bitumen

• paraffin

• petrol

Answer explanation

Paraffin is also known as kerosene.

When petrol (gasoline) is burnt in a car engine, gases are produced.

Which gas is toxic and is produced by incomplete combustion of petrol?

• carbon dioxide

• carbon monoxide

• oxides of nitrogen

• water vapour

Answer explanation

Incomplete combustion of petrol produces carbon monoxide.

Naphtha is one fraction obtained from the fractional distillation of petroleum.

What is the main use of naphtha?

• to provide feedstock for the petrochemical industry

• to provide a fuel for aircraft engines

• to provide a material for road surfaces

• to provide lubricating oils

Petroleum is fractionally distilled to produce useful fractions.

Which row matches the fraction to its use?

• A

• B

• C

• D

Answer explanation

Bitumen - for making roads

lubricating oils - for making waxes & polishes

paraffin (kerosene) - aircraft fuel

petrol (gasoline) - fuel in cars

The diagrams show the structures of four organic molecules.

Which two are members of the same homologous series?

• P and R

• P and S

• Q and R

• R and S

Answer explanation

P and S belong to the homologous series of alcohols.

Both P and S have the -OH group.

What is methane the main constituent of?

• diesel

• naphtha

• natural gas

• petrol

Answer explanation

Methane (CH₄) is the main component of natural gas.

Diesel, naphtha and petrol are made of larger alkanes, and found as liquids at room temperature.

The flow chart outlines the manufacture of poly(ethene) from crude oil.

Which process involves cracking?

• A

• B

• C

• D

Answer explanation

Process A - evaporation / boiling

Process B - fractional distillation

Process C - cracking (diesel oil consists of long-chain alkanes that can be cracked to form ethene)

Process D - addition polymerisation

The diagram shows a fractionating tower in which petroleum is separated into fractions.

What are fractions P, Q and R?

• P: diesel

  Q: bitumen

  R: petrol (gasoline)

• P: diesel

  Q: petrol (gasoline)

  R: bitumen

• P: petrol (gasoline)

  Q: bitumen

  R: diesel

• P: petrol (gasoline)

  Q: diesel

  R: bitumen

Answer explanation

Petrol (gasoline) has the lowest boiling point, followed by diesel, and then bitumen.

Petroleum is separated into a number of useful fractions by fractional distillation.

One of fractions is naphtha.

What is a use of naphtha?

• feedstock for the chemical industry

• fuel for heating and cooking

• fuel in cars

• making road surfaces

Answer explanation

Which statement about alkanes is correct?

• A molecule of propane contains two carbon atoms.

• The general formula is C_nH_2n.

• The products of complete combustion are carbon monoxide and water.

• They react with chlorine in a substitution reaction.

Answer explanation

Propane contains 3 carbon atoms.

General formula of alkanes is C_nH_2n+2.

The products of complete combustion should be carbon dioxide and water.