Organic Chemistry

Question 1

How many bonds can carbon atoms form and why?

Answer 1

It can only form 4 bonds because it has 4 electrons in its outer shell

Question 2

What is a hydrocarbon?

Answer 2

A compound made up of only hydrogen and carbon

Question 3

In what ways are a structural formula and a molecular formula different?

Answer 3

A structural formula shows atoms and bonds while a molecular formula shows just atoms

Question 4

Alkanes are ______ hydrocarbons

Answer 4

Saturated

Question 5

Alkenes are ______ hydrocarbons

Answer 5

Unsaturated

Question 6

What are saturated hydrocarbons?

Answer 6

Hydrocarbons with only single bonds between C atoms (alkanes)

Question 7

What are unsaturated hydrocarbons?

Answer 7

Hydrocarbons with a C=C double bond (alkenes)

Question 8

What are the general formulae for alkanes and alkenes?

Answer 8

Akanes: Cn H2n+2

Alkenes: Cn H2n

Question 9

How is crude oil formed?

Answer 9

From remains of marine organisms over millions of years

Question 10

How are individual hydrocarbons extracted from crude oil?

Answer 10

Fractional distillation

Question 11

What is the first step in fractional distillation?

Answer 11

Evaporation of crude oil

Question 12

Why do fractions condense at different points in a fractional distillation column?

Answer 12

Because they have different boiling points. Fractions with a high bp will condense lower in the column (longer chains of C) and fractions with a low bp will condense higher in the column (shorter chains of C)

Question 13

What happens to the properties of the gases as you rise through a fractional distillation column?

Answer 13

Burn easier - better fuels
Chain length decreases
Bpt decreases
Lighter colour

Question 14

What properties do larger molecules have? (FD)

Answer 14

High boiling point
Not very volatile
Do not flow easily
Do not ignite easily

Question 15

What properties do smaller molecules have? (FD)

Answer 15

Low boiling point
Very volatile
Flow easily
Ignite easily

Question 16

What does volatility mean?

Answer 16

How readily a substance vapourises (goes from a liquid to a gas)

Question 17

Which length chains are the most commercially valuable?

Answer 17

Short chains because they are the best fuels

Question 18

How can you solve the problem of oversupply of long chain saturated hydrocarbons after fractional distillation?

Answer 18

Cracking

Question 19

What is cracking?

Answer 19

The breaking down of long chain saturated hydrocarbons (alkanes) using heat and a catalyst

Question 20

What does cracking produce?

Answer 20

Shorter chain alkanes (better fuels) and alkanes which can be used to make plastics

Question 21

What will a combustion reaction with an alkane/alkene always produce?

Answer 21

Carbon dioxide and water

Question 22

What does hydrogen produce when it burns?

Answer 22

Water

2H2+O2->2H2O

Question 23

What can hydrogen be used for?

Answer 23

As rocket fuel and increasingly to power cars

Question 24

What are the advantages of using hydrogen as a fuel?

Answer 24

It’s renewable because it’s produced from water

Water is the only product made when it burns so it doesn’t contribute to global warming

There’s lots of it about because there’s a lot of water in the environment

Question 25

What are the disadvantages of using hydrogen as a fuel?

Answer 25

Large amounts of electricity are needed to produce hydrogen by electrolysis

Storage of fuel in the car is in heavy, pressurised containers

Forms an explosive mixture with air

Question 26

Why is using hydrogen as a fuel not completely carbon-neutral?

Answer 26

It takes a lot of electricity to carry out electrolysis to separate hydrogen from water

Question 27

How could we make hydrogen a carbon neutral fuel?

Answer 27

Generate energy for electrolysis through renewable sources e.g. wind or solar

Question 28

What is the fire triangle?

Answer 28

The 3 things needed to start and maintain a fire

Question 29

How can we apply the fire triangle to fire fighting methods?

Answer 29

Removing one of the 3 essential things that keep a fire burning
e.g. Add water -> Removes heat
Fire blanket -> Removes oxygen
Create fire break -> Removes fuel

Question 30

What are isomers?

Answer 30

Molecules with the same molecular formula but a different structural formula

Question 31

How do we name isomers?

Answer 31

Based on how many carbon atoms can be in a line

e.g. Butane has the same number of carbon atoms as methylpropane

Question 32

In what case do we use the preposition methyl-?

Answer 32

When there is one side-chain of carbon stemming from the longest chain

e.g. Methylpropane
(isomer of butane)

Question 33

In what case do we use the preposition dimethyl-?

Answer 33

When there are two side-chains of carbon in opposite directions from the longest possible chain

Question 34

In what case do we use the preposition ethyl-?

Answer 34

When there is a side chain consisting of two carbon atoms stemming from the largest possible line of carbon atoms

Question 35

How can you create a different isomer in an alkene without creating a side-chain?

Answer 35

By moving the position of the double bond

We show this by placing a number in the middle of the name
e.g. But-1-ene or But-2-ene

Question 36

How would you go about drawing an isomer from a name?

Answer 36

Start from the back of the name, create the carbon skeleton and work backwards through the name