Y11 Cracking and Fractionating

Cracking is defined as which one of the following?

• The thermal decomposition of alkAnes.

• The thermal decomposition of alkEnes.

• The separation of a mixture of alkAnes.

• The separation of a mixture of alkEnes.

Fractional distillation is a separation technique. It is best described as which one of the following?

• A physical change

• A chemical change

During cracking which of the following conditions are often required?

• High temperature

• A catalyst

• High pressure

• Low temperature

In the fractional distillation of petroleum (crude oil), the term fraction refers to what?

• A group of compounds with a similar number of carbon atoms.

• A group of compounds with similar boiling points.

• A group of compounds with similar uses.

• A group of compounds with similar molecular masses.

Which of the following are NOT the products of the cracking of hexane, C₆H₁₄?

• C₂H₄ + C₄H₁₀

• C₃H₆ + C₃H₈

• C₄H₈ + C₃H₈

• C₅H₁₀ + CH₄

Which property of the molecules in the mixture does fractional distillation take advantage of?

• Boiling point

• Melting point

• Density

• Mass

Why is cracking carried out in industry?

• Short chain alkanes are useful as fuels.

• Alkenes are useful for making plastics.

• Hydrogen formed can be used in the production of ammonia.

• All of the answers here.

In which list are the fractions of petroleum shown in order of increasing number of carbon atoms?

• Refinery gas < Gasoline < Kerosene < Residue

• Refinery gas < Kerosene < Gasoline < Residue

• Gasoline < Refinery Gas < Kerosene < Residue

• Gasoline < Refinery Gas < Residue < Kerosene

In catalytic cracking which of the following is the catalyst used?

• Silicon (IV) oxide

• Potassium manganate (VII)

• Finely divided iron

• Vanadium (V) oxide

In the fractionating column, which part is the hottest?

• The top

• The middle

• The bottom