Organic Chemistry

Question 1

What are hydrocarbons?

Answer 1

• molecules that are made up of hydrogen and carbon atoms only

Question 2

What are alkanes?

Answer 2

• a hydrocarbon

Question 3

What are the names and displayed formulas of the first five alkanes?

Answer 3

• methane: CH4
• ethane: C2H6
• propane: C3H8
• butane: C4H10
• pentane: C5H12
• Mice, Eat, Peanut, Butter, Pentane

Question 4

What is a homologous series?

Answer 4

• a group of compounds that can all be represented by the same formula

Question 5

What is the formula for all alkanes ?

Answer 5

• CnH(2n+2)

Question 6

What must a compound be to be an alkane?

Answer 6

• a saturate hydrocarbon

- saturated means it contains no double bonds

Question 7

What is complete combustion?

Answer 7

• when there is plenty of oxygen about, alkanes burn to produce carbon dioxide and water: alkane + oxygen = carbon dioxide + water (+energy)
• it releases a lot of energy and only produces two harmless waste products. gas burns with a clean blue flame

Question 8

What is incomplete combustion?

Answer 8

• when there isn’t enough oxygen, alkane combustion will be incomplete
• carbon dioxide and water are still produced, but also get carbon and carbon monoxide
• alkane + oxygen = carbon + carbon monoxide + carbon dioxide + water (+energy)
• produces a smoky yellow flame, and less energy than complete combustion

Question 9

What is a substitution reaction?

Answer 9

• chlorine and bromine react with alkanes in the presence of UV light
• a hydrogen atom from the alkane is substituted by chlorine or bromine.
• bromine and methane react together to form bromomethane

Question 10

What are alkenes?

Answer 10

• hydrocarbons that have a double bond between two of the carbon atoms in their chain

Question 11

What type of molecules are alkenes?

Answer 11

• unsaturated

- they can make more bonds, double bond can open up

Question 12

What are the first four alkenes?

Answer 12

• ethene, C2H4
• propene, C3H6
• butene, C4H8
• pentene, C5H10

Question 13

What is the general formula for alkenes?

Answer 13

• CnH2n

Question 14

What do halogens react with alkenes to form?

Answer 14

• haloakanes
• e.g. bromine and ethene react to form dibromoethane
• these are additional reactions because the C=C bond is split and a halogen atom is added

Question 15

What is the reaction between bromine and alkenes used to test?
- an addition reaction

Answer 15

• to test for carbon- carbon double bonds
• when you shake an alkene with orange bromine water, the solution becomes colourless
• this is because the bromine molecules, which are orange, are reacting with the alkene to make dibromoalkane, which is colourless