4.7.1 Carbon compounds as fuels and feedstock (will come up)

Question 1

What is crude oil

Answer 1

A mixture of compounds; a fossil fuel consisting of the remains of ancient biomass
Finite resource - cannot be replaced as it is used up

Question 2

What is a hydrocarbon

Answer 2

A compound made exclusively of carbon and hydrogen atoms

Question 3

What are alkanes

Answer 3

Saturated hydrocarbons of a general formula CnH2n+2

Question 4

What is a homologous series

Answer 4

Series of compounds with same general formula, same functional groups and similar chemical properties

Question 5

What are the first 4 alkanes

Answer 5

methane, ethane, propane and butane

Question 6

Describe the combustion of hydrocarbons

Answer 6

Exothermic reaction occurring when hydrocarbons are reacted with oxygen
Complete combustion produces carbon dioxide and water
Incomplete combustion produces carbon or carbon monoxide and water

Question 7

Physical properties of alkanes

Answer 7

First few in series are gases, then change to liquids, then to solids
In general boiling points and viscosity increase as molecules get bigger
Volatility and flammability decrease as molecules get bigger
Poor reactivity

Question 8

Explain how fractional distillation of crude oil takes place

Answer 8

Crude oil is heated and vaporised
Vapor rises up the fractioning column
The column is hotter at the bottom and cooler at the top
Hydrocarbons cool as they have different boiling points
Large molecules, high boiling points collected at bottom
Small molecules, low boiling points collected at top
This give fractions which can be used in various ways

Question 9

What is cracking

Answer 9

When large hydrocarbons are thermal broken down into smaller and useful molecules

Question 10

What type of reaction is cracking

Answer 10

Thermal decomposition

Question 11

What are the conditions for cracking

Answer 11

Reactant heated to vapor, passed over a hot catalyst (catalytic cracking)
or
heated to vapor, mixed with steam and heated to high temperatures (steam cracking)

Question 12

How are the products of cracking used

Answer 12

The products are alkanes and alkenes used as polymers and starting materials for synthesis

Question 13

What is an alkene

Answer 13

Unsaturated hydrocarbon, contains a C=C bond

General formula for alkenes is CnH2n

Question 14

What is the test for alkenes

Answer 14

Add bromine water

Colour changes from orange to colourless