DF3: Hydrocarbons

Question 1

What is crude oil?

Answer 1

A thick black liquid consisting of a mixture of hydrocarbons

Question 2

Explain the process of fractional distillation.(4)

Answer 2

• At the refinery, the crude oil is heated to vapourise it
• vapour passes into the distillation column
• Vapour rises up through the column, separating into different fractions
• as different ones condense into liquids and run off at different levels

Question 3

Does density increase/decrease up a fractionating column?

Answer 3

Decrease

Question 4

Does boiling point increase/decrease up a fractionating column?

Answer 4

Decrease

Question 5

Does chain length increase/decrease up a fractionating column?

Answer 5

Decrease

Question 6

Does volatility increase/decrease up a fractionating column?

Answer 6

Increase

Question 7

Does flammability increase/decrease up a fractionating column?

Answer 7

Increase

Question 8

Why does each fraction not have an exact boiling point?

Answer 8

Each one is a mixture of many different hydrocarbons

Question 9

Why is organic chemistry named so?

Answer 9

Many carbon compounds are found in living organisms

Question 10

What does organic chemistry include?

Answer 10

All carbon compounds except CO, CO2 and carbonates

Question 11

How many electrons does carbon have in its outershell?

Answer 11

4

Question 12

Why does carbon generally form covalent bonds?

Answer 12

If it achieved stability by becoming an ion it would be too highly charged (4+ or 4-)

Question 13

What is catenation?

Answer 13

Carbon’s ability to form strong covalent bonds with itself to give chains and rings of itself

Question 14

What does catenation lead to?

Answer 14

The limitless variety of organic compounds

Question 15

Define “hydrocarbon”

Answer 15

Compounds containing only carbon or hydrogen

Question 16

What is the general formula for hydrocarbons?

Answer 16

CxHy

Question 17

Define “aromatic”

Answer 17

Compounds containing one/more benzene rings

Question 18

Define “aliphatic”

Answer 18

Compounds not containing any benzene rings

Question 19

Define “functional group”

Answer 19

Modifiers responsible for the characteristic chemical reactions of molecules

Question 20

Define “saturated”

Answer 20

A compound with no bonds available for bonding

Question 21

Define “unsaturated”

Answer 21

A compound containing bonds that can be broken open

Question 22

Define “homologous series”

Answer 22

A series of compounds with the same general molecular formula

Question 23

Are alkanes saturated?

Answer 23

Yes

Question 24

How many bonds does carbon form?

Answer 24

4

Question 25

Are alkanes aliphatic?

Answer 25

Yes

Question 26

What is the general formula for alkanes?

Answer 26

CnH2n+2

Question 27

Name the first ten alkanes

Answer 27

- Methane - Ethane - Propane - Butane - Pentane - Hexane - Heptane - Octane - Nonane - Decane

Question 28

What is the relationship between alkane chain length and tendency to become a solid and why?

Answer 28

As chain length increases, the tendency towards a solid also increases because the boiling point increases

Question 29

What state are alkanes n= 1 - 4 in?

Answer 29

Colourless gases

Question 30

What state are alkanes n=5 - 16 in?

Answer 30

Colourless liquids

Question 31

What state are alkanes n=17+ in?

Answer 31

White waxy solids

Question 32

Do alkanes mix well with water?

Answer 32

No they form two separate layers

Question 33

Why do alkanes not mix well with water?

Answer 33

Water contains polar molecules that attract each other and prevent alkane molecules mixing with them

Question 34

What are cycloalkanes?

Answer 34

A ring of carbon atoms with two hydrogens attached to each carbon

Question 35

What is the general formula for alkanes?

Answer 35

CnH2n+2

Question 36

Are cycloalkanes saturated?

Answer 36

Yes

Question 37

Are alkenes saturated and why?

Answer 37

No - the carbon double bond can open up and bond with more hydrogens

Question 38

What is the general formula for alkenes?

Answer 38

CnH2n

Question 39

Are alkenes aliphatic?

Answer 39

Yes

Question 40

What is the general formula for cycloalkenes?

Answer 40

CnH2n-2

Question 41

Are cycloalkenes aliphatic?

Answer 41

Yes

Question 42

Are cycloalkenes saturated?

Answer 42

No

Question 43

What is the formula of benzene?

Answer 43

C6H6

Question 44

How many carbons and double bonds does a benzene ring contain?

Answer 44

6 carbons and 3 double bonds

Question 45

Why are benzene rings more stable (less reactive) than expected?

Answer 45

The double bond electrons are delocalised around the carbon ring, unattached to any particular carbon

Question 46

Is benzene aliphatic?

Answer 46

No - aromatic

Question 47

Is benzene saturated?

Answer 47

No

Question 48

Is alcohol a hydrocarbon?

Answer 48

No

Question 49

What is the general formula for alcohols?

Answer 49

CnH2n+1OH

Question 50

What is the functional group for alcohols?

Answer 50

The hydroxl group (-OH) which can be attached to any carbon atom on the chain

Question 51

What is a general formula?

Answer 51

A formula that can describe any member of a family of compounds

Question 52

What is a molecular formula?

Answer 52

The actual number of atoms of each element in a molecule

Question 53

What is the shortened structural formula?

Answer 53

A formula showing the atoms, carbon by carbon with the attached hydrogens and functional groups

Question 54

What is the structural formula?

Answer 54

Shows how all the atoms are arranged and all the bonds between them

Question 55

What is the skeletal formula?

Answer 55

Shows the bond between the carbon skeleton only, with any functional groups. The hydrogen and carbon atoms are not shown.

Question 56

Why is giving systematic names important?

Answer 56

It allows for the full structural formula of a compound to be determined.

Question 57

What is the formula of methyl?

Answer 57

CH3

Question 58

What is the formula for all alkyls after methyl?

Answer 58

CH3 + CH2 for every carbon atom

Question 59

What is the prefix for two identical sidechains?

Answer 59

Di

Question 60

What is the prefix for three identical sidechains?

Answer 60

Tri

Question 61

What is the prefix for four identical sidechains?

Answer 61

Tetra