Fuels and Heats of Reaction Model Questions & Solutions

1. How could one show that ethene undergoes an addition reaction with bromine water?

Bubble ethene gas through bromine water.

Colour change goes from brown to colourless - test for unsaturation.

2. Define structural isomer

A compound with the same molecular formula but different structural formula.

3. Identify the hydrocarbon gas produced by anaerobic bacterial

decomposition of either animal waste or vegetation

Methane

4. State Hess's law

The heat change for a reaction depends only on the initial and final states

5. Write a balanced chemical equation for dehydrocylisation of heptane to form methylbenzene

C7H16 → C7H8 + 4H2

6. State the four processes required to increase the octane number

Dehydrocylisation, catalytic cracking, isomerisation and adding oxygenates

7. Give a major use for kerosene

Aviation fuel

8. Give a major use for residue

Taring the road

9. What occurs during the secondary sewage treatment?

Oxidation and aeration.

The use of micro-organisms to breakdown organic matter.

10. Name the two reference hydrocarbons

Heptane = 0

2,2,4 - trimethylpentane = 100

11. Name the oil refining process to converts octane into 2,2,4 -

trimethylpentane

Isomerisation

12. Give two structural features of hydrocarbons with high octane numbers

Short carbon chains, branched or cyclic.

13. Explain the term homologous series

The general formula differs by CH2. They contain the same functional group and

have similar chemical properties.

14. State a major use for ethene and ethyne

Ethene: Ripening fruit

Ethyne: Welding and cutting

15. Give two advantages to adding oxygenates, such as ethanol to fuel

It increases the octane number

It burners cleaner - less pollution to the environment.

16. Give two properties of hydrogen that make it a fuel of choice for

space shuttles

1. Light - low molecular mass

2. Very high octane number

17. State a disadvantage with hydrogen as a fuel

Difficult to transport and is expensive

18. Give two ways in which hydrogen gas is produced

Steam reforming

Electrolysis

19. Define heat of combustion

The heat change when one mole of a substance is burned in excess oxygen.

20. Name a laboratory equipment piece to measure the heat of

combustion

Bomb calorimeter

21. Explain the term isomerisation

The changing to different structures - making it more branched to increase

the octane number.

22. Explain the term octane number

The measure of tendency of a fuel to auto-ignite

23. Why was lead added to fuel and why was it later discontinued?

To increase the octane number. It is carcinogenic.

24. What is the nature of chemicals that make up the bulk of crude oil?

They are mostly hydrocarbons

25. Give a major use for naphtha or light gasoline

Petrol

26. Define the heat of formation

The heat produced when one mole of a compound is formed from its

elements.