organic chemistry (p2)

Question 1

What is crude oil?

Answer 1

a mixture of a large number of compounds, most of which are hydrocarbon

Question 2

How was crude oil formed?

Answer 2

from the remains of organisms that lived and died millions of years ago (mainly plankton which was buried in the mud)

Question 3

Is crude oil a finite or renewable resource?

Answer 3

Finite

Question 4

What is a hydrocarbon?

Answer 4

a compound made up of carbon and hydrogen only

Question 5

Why type of bond joins the carbon and hydrogen atoms in a hydrocarbon

Answer 5

covalent bond

Question 6

What is an organic compound?

Answer 6

compounds containing carbon atoms covalently bonded to other atoms

Question 7

What is a homologous series?

Answer 7

a family of organic compounds with the same general formula and similar properities

Question 8

What is the general formula for alkanes?

Answer 8

CₙH₂ₙ₊₂

Question 9

What are the names of the first four members of the alkanes?

Answer 9

Methane
Ethane
Propane
Butane

Question 10

What do the names of alkanes always end in?

Answer 10

-ane

Question 11

How many bonds does carbon form in a compound?

Answer 11

four

Question 12

How many bonds does hydrogen form in a compound?

Answer 12

1

Question 13

How are the different compounds in crude oil separated?

Answer 13

Fractional distillation

Question 14

What is a fraction?

Answer 14

a mixture of hydrocarbons with a similar number of carbon atoms

Question 15

What are the products of fractional distillation used for?

Answer 15

• fuels
• starting materials for the petrochemical industry

Question 16

What are the names of some fractions produced in fractional disillation?

Answer 16

• petrol
• diesel oil
• kerosene
• heavy fuel oil
• liquefied petroleum gases

Question 17

What useful materials are produced by the petrochemical industry?

Answer 17

• solvents
• lubricants
• polymers
• detergents

Question 18

How does the temperature of the fractionating column change as you move from bottom to top?

Answer 18

the temperature decreases

Question 19

What happens when crude oil is heated before entering the fractionating column?

Answer 19

the crude oil evaporates

Question 20

What happens to the crude oil vapours as they travel up the fractionating column?

Answer 20

• they cool and condense
• when they condense they are collected

Question 21

Describe how crude oil is seperated in fractional distillation

Answer 21

• Crude oil is heated and it evaporates
• The crude oil vapours enter the fractionating column and travel upwards
• The temperature of the fractionating column decreases towards the top
• As the vapours travel up they cool and condense at different temperatures depending on their boiling points

Question 22

Where are the long chain hydrocarbons collected in fractional distillation?

Answer 22

At the bottom of the fractionating column

Question 23

Where are the short chain hydrocarbons collected in fractional distillation?

Answer 23

At the top of the fractionating column

Question 24

What causes the hydrocarbons to sepeate in fractional distillation?

Answer 24

They have different boiling points and so condense at different levels

Question 25

When will the hydrocarbons condense in the fractionating column?

Answer 25

When the temperature drops below their boiling point

Question 26

Why do short chain hydrocarbons collect at the top of the fractionating column?

Answer 26

They have low boiling points and so condense at lower temperatures

Question 26

Why do large chain hydrocarbons collect at the bottom of the fractionating column?

Answer 26

They have large boiling points and so condense at higher temperatures

Question 27

If a hydrocarbon boils at 300 ᵒC, what temperature will it condense at?

Answer 27

300 ᵒC

Question 28

What bonds break when hydrocarbons melt and boil?

Answer 28

Intermolecular forces

Question 29

What type of force holds hydrocarbon molecules together?

Answer 29

Intermolecular forces

Question 30

What does viscosity it mean?

Answer 30

How much a fluid resists flow (how gloopy it is)

Question 31

What does volatility mean?

Answer 31

How easy it is to turn a substance into a gas

Question 32

What does flammability mean?

Answer 32

How easy it is to ignite a substance

Question 33

As hydrocarbon molecules get bigger, what happens to their viscosity?

Answer 33

increases

Question 34

As hydrocarbon molecules get bigger, what happens to the boiling point?

Answer 34

increases

Question 35

As hydrocarbon molecules get bigger, what happens to their flammability?

Answer 35

decreases

Question 36

Why does the viscosity of hydrocarbons increase as the hydrocarbon molecules get bigger?

Answer 36

As the hydrocarbon molecules get bigger, the intermolecular forces get stronger and move over each other less easily

Question 37

Why does the boiling point of hydrocarbons increase as the hydrocarbon molecules get bigger?

Answer 37

As the hydrocarbon molecules get bigger, the intermolecular forces get stronger and require more energy to break

Question 38

Which are better fuels - long or short chain hydrocarbons?

Answer 38

Short chain (they are more flammable)

Question 39

What is combustion?

Answer 39

reaction with oxygen (burning)

Question 40

What is complete combustion?

Answer 40

burning in a plentiful supply of oxygen

Question 41

What are the reactants in complete combustion of a hydrocarbon?

Answer 41

hydrocarbon + oxygen

Question 42

What are the products in complete combustion of a hydrocarbon?

Answer 42

carbon dioxide + water

Question 43

What is cracking?

Answer 43

the breaking of longer chain hydrocarbons into shorter, more useful hydrocarbons

Question 44

Why do we 'crack' hydrocarbons?

Answer 44

to produce smaller, more useful molecules

Question 45

What is the reactant in cracking?

Answer 45

longer chain alkanes

Question 45

Why is cracking a thermal decomposition reaction?

Answer 45

the longer chain hydrocarbons breakdown when heated

Question 45

What are the products in cracking?

Answer 45

a shorter chain alk𝗮𝗻𝗲 and a short chain alk𝗲𝗻𝗲

Question 45

What is thermal decomposition?

Answer 45

the breakdown of a substance when it is heated

Question 46

Name two types of cracking

Answer 46

* steam * catalytic cracking

Question 47

Describe the process of steam cracking

Answer 47

* Long chain hydrocarbons are heated and they evaporate * The hydrocarbon vapour is heated to a very high temperature and mixed with steam * The hydrocarbons are broken into smaller hydrocarbons

Question 48

Describe the process of catalytic cracking

Answer 48

* Long chain hydrocarbons are heated and they evaporate * The hydrocarbon vapour is then passed over a catalyst * The hydrocarbons are broken into smaller hydrocarbons

Question 49

[𝗛𝗶𝗴𝗵𝗲𝗿 𝘁𝗶𝗲𝗿] What is the general formula for alkenes?

Answer 49

CₙH₂ₙ

Question 50

Which are more reactive: alkanes or alkenes?

Answer 50

Alkenes

Question 51

What is used to test for alkenes?

Answer 51

bromine water

Question 52

What colour is bromine water?

Answer 52

orange

Question 52

What colour does bromine water turn when added to alkenes?

Answer 52

colourless

Question 53

What colour does bromine water turn when added to alkanes?

Answer 53

stays orange

Question 54

What are alkenes used for?

Answer 54

to make polymers and as the starting material when making many other chemicals