Topic 7- Organic chemistry

Question 1

What is crude oil?

Answer 1

a mixture of compounds, a fossil fuel consisting of the remains of ancient biomass.

Question 2

What is a hydrocarbon?

Answer 2

A compound made up exclusively of hydrogen and carbon atoms.

Question 3

What are alkanes?

Answer 3

general formula of CnH 2n+2
saturated hydrocarbons (each carbon atom forms four single covalent bonds.

Question 4

What is a homologous series?

Answer 4

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

Question 5

Describe the combustion of hydrocarbons

Answer 5

Hydrocarbon combustion refers to the chemical reaction where a hydrocarbon reacts with oxygen to create carbon dioxide, water, and heat.
Incomplete combustion produces carbon or carbon monoxide and water.

Question 6

Describe the physical properties of alkanes

Answer 6

• First few in the series are gases, then change to liquids, then to solids.
• In general boiling points and viscosity increase as molecules get bigger.
• hydrocarbons with shorter carbon chains have lower boiling points, more flammable less viscous
• poor reactivity

Question 7

Explain how fractional distillation of crude oils take place

Answer 7

Crude oil is heated and vaporised, vapour rises up the fractionating column where it is hotter at the bottom and cooler at the top. Hydrocarbons cool as the go up the column and condense at different heights.
large molecules-high boiling points- collected at the bottom.
small molecules- low boiling points- collected at the top.

Question 8

What is cracking?

Answer 8

When large hydrocarbons are thermally broken down into smaller and useful molecules.

Question 9

What type of reaction is cracking?

Answer 9

Thermal decomposition- chemical reaction where heat is a reactant- endothermic.

Question 10

What are alkenes?

Answer 10

unsaturated hydrocarbon. containa C=C bond.

CnH2n

Question 11

What is the test for alkenes?

Answer 11

Add bromine water, changes from orange to colourless.

Question 12

Describe the combustion of alkenes

Answer 12

Complete- Produces carbon dioxide and water.

Incomplete- produces water carbon dioxide, carbon(soot) causing a smoky flame.

Question 13

State characteristics of methanol, ethanol, propanol and butanol.

Answer 13

• dissolves in water to form a neutral solution
• reacts with sodium to form hydrogen
• burns in oxygen
• reacts with carboxylic acids in presence of acide catalysts to form esters.

Question 14

oxidation of alchohol

Answer 14

leads to carboxylic acid