C9

Question 1

What is crude oil?

Answer 1

• Mixture of many different compounds
• most of these are hydrocarbons - contain only hydrogen and carbon atoms

Question 2

What are alkanes?

Answer 2

• saturated hydrocarbons
•contain as many hydrocarbons as possible in their molecules

General formula = CnH(2n+2)

Question 3

What are the most useful hydrocarbons?

Answer 3

• short chain
• ignite easily and burn well - good fuels

Question 4

What is fractional distillation?

Answer 4

• when crude oil is separated into hydrocarbons with similar BPs, called fractions

Question 5

How does fractional distillation work?

Answer 5

• crude oil is heated and enters the fractionating column as hot vapour
• temperature decreases going up
• gases move up the column and hydrocarbons condense when they reach their BPs.

Question 6

Which hydrocarbons have the lowest BP?

Answer 6

Smallest hydrocarbons

Question 7

Two methods of cracking

Answer 7

• vapor is passed over a hot catalyst
•vapour is mixed with steam and heated to a very high temperature

Question 8

How can we test for alkenes?

Answer 8

React them with orange bromine water - should turn colourless

Question 9

Effect of increasing carbon atoms in an alkane

Answer 9

Increases its viscosity (thickness)

Question 10

Burning hydrocarbon fuels key points

Answer 10

• When hydrocarbon fuels are burned in plenty of air, the carbon and hydrogen in the fuel are completely oxidised. They produce carbon dioxide and water.
• You can test the gases formed in complete combustion of a nydrocaroon: the carbon dioxide turns limewater cloudy, and the water turns blue cobalt chloride paper pink (or white anhydrous copper sulfate blue).
• Incomplete combustion of a
nyarocaroon produces carbon monoxide (a toxic gas) as one of its products.

Question 11

What is a hydrocarbon?

Answer 11

A molecule that is made up of only hydrogen and carbon atoms.