Alkanes and Alkenes

Question 1

What is the general formula for alkanes?

Answer 1

Question 2

Name the first four alkanes and write down their molecular formula

Answer 2

Methane - CH₄

Ethane - C₂H₆

Propane - C₃H₈

Butane - C₄H₁₀

Question 3

What type of bond are formed between carbon and hydrogen atoms in alkanes?

Answer 3

Covalent bonds

Question 4

What is the displayed formula of ethane?

Answer 4

Question 5

Why are alkanes saturated hydrocarbons?

Answer 5

Alkanes are saturated because all the C-C bonds are single bonds and they are hydrocarbons because the contain only carbon and hydrogen atoms

Question 6

What is the general formula for alkenes?

Answer 6

Question 7

Name the first four alkenes and write their molecular formulae?

Answer 7

Ethene - C₂H₄

Propene - C₃H₆

Butene - C₄H₈

Pentene - C₅H₁₀

Question 8

Why are alkenes unsaturated hydrocarbons?

Answer 8

They are compounds made up of only carbon and hydrogen atoms and they contain double carbon bonds, C=C

Question 9

What is a functional group?

Answer 9

The group of atoms responsible for the main chemical porperties properties of a compund.

Question 10

What functional group do alkenes contain?

Answer 10

C=C double bond

Question 11

What is the difference between but-1-ene and but-2-ene?

Answer 11

But-1-ene and but-2-ene are both alkenes with 4 carbons bu the C=C bond is found between different carbons in the chain. In but-1-ene, the double bond is between the first and second carbon whereas in but-2-ene, it is between the second and third carbon in the chain

Question 12

What is the displayed formula of 1,2-dibromoethane

Answer 12

Question 13

How can bromine water be used to distinguish between alkanes and alkenes?

Answer 13

When bromine water is added to an alkane, the solution remains orange. When bromine water is added to an alkene, the solution changes from orange to colourless.

Question 14

Why do alkenes decolourise bromine water?

Answer 14

Alkenes are unsaturated. The double bond allows alkenes to react with bromine to form a bromoalkane

Question 15

What is produced when a hydrocarbon is completely combusted? Describe what happens to the carbon and hydrogen

Answer 15

Water and carbon dioxide are produced. Carbon and hydrogen are oxidised.

Question 16

Energy is released when hydrocarbons undergo complete combustion. What type of reaction is occurring?

Answer 16

An exothermic reaction.

Question 17

What is a polymer?

Answer 17

A substance of high average relative molecular mass made up of small repeating units.

Question 18

How are polymers made?

Answer 18

By linking together lots of small molecules (monomers) to form a long chain.

Question 19

What is the name of the process in which ethene molecules join together to form a polymer?

Answer 19

Addition polymerisation.