Organic Chemistry

Question 1

What is a hydrocarbon?

Answer 1

it is a compound made up of only hydrogen and carbon atoms

Question 2

What is the alkane formula?

Answer 2

CnH2n+2

Question 3

What is a homologous series?

Answer 3

a group of organic compounds that react in similar ways

Question 4

What are alkanes?

Answer 4

they are fully saturated hydrocarbons that are a homologous series.

Question 5

What is a saturated compound/hydrocarbon?

Answer 5

it has the maximum amount of single bonds (carbon is fully saturated in a hydrocarbon when it makes 4 bonds, ie max amount of bonds)

Question 6

What are the first 5 alkanes called?

Answer 6

Methane, Ethane, Propane, Butane, Pentane

Question 7

Draw methane and propane as displayed formula.

Answer 7

Methane: CC - H - C CPropane: C C C C - H - H - H - C C C C

Question 8

How do the properties of Hydrocarbons change as the length of the carbon chain changes?

Answer 8

The longer the chain, the more viscous it isThe longer the chain, the less volatile it is (higher boiling points as length continues)The longer the chain, the less flammable it isAffects how they are used for fuels.

Question 9

How does the length of a hydrocarbon affect how they are used in fuels?

Answer 9

Short hydrocarbons with lower boiling points are used as ‘bottled gases’, stored under pressure as liquid in bottles.

Question 10

What is the equation for complete combustion?

Answer 10

Hydrocarbon + oxygen -> carbon dioxide + water (+ energy)

Question 11

What is oxidation?

Answer 11

the gain of oxygen, loss of electrons

Question 12

During complete combustion what happens to the hydrocarbon?

Answer 12

Both the hydrogen and carbon from the hydrocarbon are oxidised

Question 13

Why are hydrocarbons used/good as fuels?

Answer 13

Due to the high amount of energy they release when they completely combust

Question 14

Write the balanced equation for the complete combustion of methane (CH4)

Answer 14

CH4 + 2O2 -> CO2 + 2H2O

Question 15

What is fractional distillation?

Answer 15

it is a process which can be used to seperate Hydrocarbon fractions.

Question 16

What is crude oil?definition

Answer 16

It is a fossil fuel, formed over millions of years due to high temp and pressure.

Question 17

Are fossil fuels renewable/ infinite resources?

Answer 17

No. Fuels like coal, oil and gas are are non-renewable fuels which are non-finite

Question 18

What is crude oil?in terms of hydrocarbons

Answer 18

It is a mixture of lots of different hydrocarbons, which are mainly alkanes.

Question 19

What is the process of fractional distillation?

Answer 19

• The oil is heated until most of it has evaporated into gas- the gases enter the fractioning column- In the column there is a temperature gradient (hot at the bottom, colder as you go up)-Longer hydrocarbons have higher boiling points, so as the gases rise up the column, they condense back to a liquid at a lower point than shorter hydrocarbons, which condense at the top of the column- the crude oil is now separated into different fractions, which all have a similar amount of carbon atoms thus why they have a similar boiling point.

Question 20

Why do some hydrocarbons condense earlier in the fractioning column?

Answer 20

they have higher boiling points, so they condense when the temperature becomes too low as they rise up as a gas. This is because of the high amount of carbon atoms they have, giving them a higher boiling point.

Question 21

What are some uses of crude oil?

Answer 21

• oil for fuel for transport- lubricants, polymers, solvents

Question 22

What is cracking?

Answer 22

Its the splitting up of long hydrocarbon chains to make them into shorter, more valuable chains.

Question 23

Why are short hydrocarbon chains good fuels?

Answer 23

They are flammable so combust fully more easily, therefore are also in high demand.

Question 24

What are some benefits to cracking?

Answer 24

• create more in demand, valuable short hydrocarbon chains- use up the less useful long chain hydrocarbons

Question 25

What is the cracking equation?

Answer 25

Long chain hydrocarbon -> shorter chain hydrocarbon (alkAne) + an alkEne

Question 26

What type of reaction is cracking?

Answer 26

it is a thermal decomposition reaction, which breaks down molecules by heating them up

Question 27

What are the types of cracking?

Answer 27

Steam cracking and catalytic cracking

Question 28

What is catalytic cracking?

Answer 28

• heat long chain hydrocarbons to vaporise them (turn to gas)- pass the vapour over a hot powdered aluminium oxide catalyst- the long chain hydrocarbon splits on the catalyst

Question 29

What is steam cracking?

Answer 29

-vaporise the hydrocarbons, mis them with steam- heat them to a very high temperature

Question 30

What are alkenes?

Answer 30

They are unsaturated hydrocarbons in a homologous series. They have 2 less hydrogens than a alkane due to their double bond ( C=C)

Question 31

What does unsaturated mean?

Answer 31

a not fully bonded molecule as it doesnt have the maximum amount of single bonds (double bonds instead)

Question 32

What is the alkene formula?

Answer 32

CnH2n

Question 33

Why are alkenes more reactive than alkanes?

Answer 33

The alkene C=C double bond can open up, creating a single bond, which allows them to bond with other atoms.

Question 34

What are the first 4 alkenes?

Answer 34

Ethene, Methene, Butene, Pentene

Question 35

What is incomplete combustion?

Answer 35

When there isn’t enough oxygen for a complete combustion reaction, creating carbon monoxide as an extra product

Question 36

What is the incomplete combustion formula?

Answer 36

Alkene + oxygen -> carbon + carbon monoxide + carbon dioxide + water