Organic Chemistry

Question 1

What is a hydrocarbon ?

Answer 1

A compound consisting of

Carbon and hydrogen only

Question 2

What is a fraction ?

Answer 2

The liquid collected at each level of fractional distillation ; they have a similar molecular structure

Question 3

What is the relationship between the length of a hydrocarbon chain and physical properties ?

Answer 3

• the long the chain the higher the boiling point
• the longer the chain the more viscous the substance
• the longer the chain the less volatile the substance is

Question 4

Why are short chain hydrocarbons more expensive than long chain hydrocarbons ?

Answer 4

• they are more useful in general because more flammable

- less common that long chains

Question 5

Describe basic steps of industrial fractional distillation

Answer 5

-crude oil is heated outside fractioning column and enters as a vapour
-vapour cools at set boiling point and is collected as a fraction
-each fraction has a tray with holes so the vapour can keep travelling
-the temperature cools
as it gets higher
-refinery gasses are collected at the top

Question 6

Name all of the fractions in order from largest to smallest molecule

Answer 6

• Bitumen
• Fuel oil
• Diesel oil
• Kerosene
• Naptha
• Gasoline
• refinery gasses

Question 7

Whats the trends in small and large molecules ?

Answer 7

Small:
-low boiling point
-low viscosity
-volatile
-ignites easily
Large:
-high boiling point
-not very volatile
-high viscosity
-difficult to ignite

Question 8

Whats an Alkane ?

Answer 8

Hydrocarbons with the general formula CnH2n+2

Question 9

What is a homologous series ?

Answer 9

is a group of hydrocarbons with similar chemical properties and show a trend in physical properties

Question 10

Name the different alkanes , the first 6 carbon variations

Answer 10

CH4 -Methane
C2H6-ethane
C3H8-propane
C4H10-Butane
C5H13-pentane
C6H14-hexane

Question 11

Whats the molecular formula , displayed formula

Answer 11

Molecular - CH4
Displayed formula-drawing of all bonds
Structural-drawing with compounds

Question 12

Why are alkane molecules easy to break apart

Answer 12

Intermolecular forces hold them together bot covalent bonds so because they are small molecules there arent very strong intermolecular forces

Question 13

Why is the boiling point of long chain hydrocarbons higher than short chain ?

Answer 13

I-more points of contact between molecules
-stronger intermolecular forces
-need more
Energy to overcome

Question 14

What is an isomer ?

Answer 14

A hydrocarbon with the same molecular formula but different structural and displayed formula

Question 15

What is crude oil ?

Answer 15

A mixture of hydrocarbons

Question 16

Hydrocarbon + oxygen ->

Complete combustion

Answer 16

Water + co2

Question 17

Hydrocarbon+oxygen–>

Incomplete combustion

Answer 17

Water +carbon monoxide +carbon /soot

Question 18

What happens when anhydrous copper sulphate comes in contact with water

Answer 18

It goes from a white powder to a blue

Question 19

Why do longer hydrocarbon chains create more soot?

Answer 19

-more oxygen needed for complete combustion
-incomplete combustion more likely due to more
Molecules

Question 20

What does the word saturated mean ?

Answer 20

Only single bonds

Question 21

How is crude oil formed ?

Answer 21

• millions of years ago
• dead animals and plants fall to bottom of sea and covered in mud
• pressure , temperature and anaerobic conditions turn the remains to crude oil
• its found in pockets and will rise if let out of the sea

Question 22

Whats the difference between lab fractioning columns and industrial ?

Answer 22

• larger column in industrial

- industrial heat crude oil to vapour first

Question 23

What is an alkene ?

Answer 23

An unsaturated compound with the formula CnH2n , normally have one double bonded carbons

Question 24

Which is more reactive alkanes or alkenes ?

Answer 24

Alkenes are more reactive because it requires less energy to overcome a double bond than two single bonds

Question 25

What does halogenation of an alkane require ?

Answer 25

Uv rays

Question 26

Whats the test for alkenes ?

Answer 26

Alkenes will de colourise bromine water

Question 27

What is cracking ?

Answer 27

Breaking long chain hydrocarbons down into short chains

Question 28

What conditions are needed for cracking ?

Answer 28

• temperature of 600-700 degrees

- a catalyst , aluminium oxide

Question 29

Whats the products of cracking ?

Answer 29

Alkanes and alkenes