Organic Chemistry/Chemical Analysis random revision (pages 150-155)

Question 1

Which alkane is represented by the displayed formula below?

       H       H
        l         l H ----  C  ----  C ----  H
       l          l
      H        H

Answer 1

Ethane

Question 2

How does the viscosity of short-chain hydrocarbons compare to that of long-chain hydrocarbons?

Answer 2

Short-chain hydrocarbons are less viscous.

Question 3

Describe the relationship between carbon chain length and the flammability of hydrocarbons?

Answer 3

The shorter the carbon chain, the more flammable the hydrocarbon.

Question 4

What gas does an alkane react with in a combustion reaction?

Answer 4

Oxygen

Question 5

Crude oil is a ‘finite resource’ What does this mean?

Answer 5

it could eventually run out.

Question 6

Explain why longer hydrocarbons drain out of the fractionating column earlier than shorter hydrocarbons?

Answer 6

Longer hydrocarbons have higher boiling points than shorter hydrocarbons, so they condense into liquids earlier on in the column where it is hotter.

Question 7

Name three fractions of curde oil?

Answer 7

Any three from e.g.:

Bitumen
Heavy fuel oil
Diesel Oil
Kerosene
Petrol
LPG (Liquefied Petoleum Gas)

Question 8

Give two examples of useful materials that are produced from petrochemicals?

Answer 8

Any two from: e.g.

Polymers (e.g. plastics)
Fuels
Lubricants
Solvents
Detergents

Question 9

Why is there a higher demand for short-chain hydrocarbons than for long-chain hydrocarbons?

Answer 9

Short-chain hydrocarbons tend to be more useful than long-chain hydrocarbons as, for example, they are more flammable so make good fuels.

Question 10

Give two methods of cracking long-chain alkanes?

Answer 10

Steam cracking and catalytic cracking.

Question 11

True or false? Long-chain hydrocarbons must be cooled to turn them into solids before they can be cracked. Explain your answer?

Answer 11

False. Long-chain hydrocarbons are heated to turn them into a gas before they are cracked.