How does a fractionating column separate crude oil?

• By chain length alone
• By boiling range in a temperature gradient
• By particle size through filters

Which account describes the formation of crude oil?

• Volcanic rocks melted into oil during eruptions over the last hundred years.
• River water changed into oil as sunlight dried the river during summer.
• Buried ancient organisms changed under heat and pressure over millions of years.

For similar hydrocarbons under the same conditions, longer chains generally have greater viscosity and lower volatility.

Circle one:   True   False

A cracking equation is C16H34 -> C12H26 + X. Which formula for X conserves carbon and hydrogen atoms?

• C4H6
• C4H4
• C4H8

Why is petrol collected higher in the column while bitumen remains near the base?

• Petrol is less dense, so it floats above bitumen.
• Petrol has a lower boiling range than bitumen.
• Petrol is made by cracking bitumen inside the column.

Which conditions describe catalytic cracking of vaporised larger hydrocarbons?

• High temperature with steam, but no catalyst
• High temperature over a suitable catalyst
• Low temperature over a suitable catalyst

At the same temperature, fraction A flows and vaporises more readily than B. For similar hydrocarbons, which interpretation fits the usual trend?

• A tends to have shorter chains than B.
• A tends to have longer chains than B.
• A and B must have the same chain length.

A refinery has surplus heavy fractions and greater demand for smaller fuels and alkenes. Why use cracking?

• It converts larger molecules into smaller ones.
• It separates the surplus by repeated boiling and condensation.
• It joins smaller molecules to form larger hydrocarbon chains.