Organic Chemistry 1

Question 1

Hydrocarbon definition

Answer 1

Compound containing carbon and hydrogen ONLY

Question 2

Saturated definitions

Answer 2

Contains single covalent bonds between carbon atoms

Question 3

Are alkanes saturated or unsaturated

Answer 3

Saturated hydrocarbons

Question 4

What is the general formula of alkanes

Answer 4

CnH2n + 2

Question 5

What is the empirical formula

Answer 5

simplest whole number ratio of atoms of each element in a compound

Question 6

What is a molecular formula

Answer 6

number of atoms of each different element in a molecule (tells you nothing about the way they are joined)

Question 7

What is the structural formula

Answer 7

shows how the atoms are joined (bonded)

Question 8

What is the displayed formula

Answer 8

shows ALL bonds and ALL atoms in molecule

Question 9

Name the alkanes in the order of the number of the carbons in the molecules

Answer 9

• Methane
• Ethane
• Propane
• Butane
  -Pentane

Question 10

What happens to the boiling point as the chain length increases

Answer 10

Boiling point increases

Question 11

What are the characteristics of the homologous series

Answer 11

1. Members differ by a CH2 group
2. Similar chemical properties (i.e. reactivity)
3. Gradual trend in physical properties
4. Same functional group

Question 12

Isomer definition

Answer 12

Isomers are compounds with the same molecular formula but different structural formulae

Question 13

Are alkenes saturated or unsaturated

Answer 13

They are unsaturated hydrocarbons

Question 14

Unsaturated definition

Answer 14

Contains at least one double covalent bond between carbon atoms

Question 15

What is the general formula of alkenes

Answer 15

CnH2n

Question 16

How are alkenes produced

Answer 16

By cracking alkanes

Question 17

Why are alkenes more reactive then alkanes

Answer 17

The double bond can break to form 2 single bonds so add other atoms (addition reaction)

Question 18

Describe a test to distinguish between butane and butene

Answer 18

• Add Bromine water into the samples
• If solution decolourises from orange it is butene
• If solution stays orange it is butane

Question 19

What type of reaction happens with alkenes

Answer 19

Addition reactions

Question 20

What type of reaction happens with alkanes

Answer 20

Substitution reaction

Question 21

What will make alkanes react

Answer 21

UV light

Question 22

Explain the process of fractional distillation

Answer 22

1. Oil is heated to about 450 °C where it vaporizes then pumped into the bottom of a tall tower called a fractionating column.​
2. The column is very hot at the bottom but much cooler at the top. As the vaporized oil rises, it cools and condenses.​
3. Heavy fractions (containing large molecules) have a high boiling point and condense near the bottom of the column. ​
4. Lighter fractions (containing small molecules) have a lower boiling point and condense further up the column.​
5. The different fractions are collected at different heights.

Question 23

Compare and contrast the reactions of alkanes and alkenes with halogens using the reactions of ethane and ethene with bromine as examples. Include reaction condition, types of reactions and names of products.

Answer 23

Alkanes:
-Needs UV light
- Substitution reaction to produce - bromoethane + Hydrogen bromide
-Be able to name the products
-SUBSTITUTION reaction

Alkenes:
-No UV required – reaction occurs readily at room temp
- Addition reaction to produce 1,2-dibromoalkane
- Be able to name the product
- ADDITION reaction

Question 24

Name the different fractions of crude oil from top to bottom

Answer 24

• Refinery gases
• Gasoline (Fuel for car engines)
• Kerosine (aeroplane fuel)
• Diesel (fuel for lorries)
• Fuel oil (ship fuel)
• Bitumen (road surfaces)

Question 25

Explain the relationship between molecule size and boiling point

Answer 25

The larger the hydrocarbon, the higher its boiling point - Intermolecular forces between large molecules are stronger than the intermolecular forces between small molecules.​ - Therefore, more energy is needed to break the forces between large molecules, and so the boiling point is higher.

Question 26

How do the colour of the fractions change with the size of the molecule

Answer 26

As the molecule gets SMALLER the colour of the fraction becomes lighter, from dark brown to light brown, orange/yellow and transparent

Question 27

How does the size of the hydrocarbon affect the viscosity

Answer 27

The longer the hydrocarbon in a fraction the more viscous the fraction will be. This is because the longer chains of large hydrocarbon molecules have stronger intermolecular forces and are more easily entangled

Question 28

How does the size of the hydrocarbon affect the volatility and flammability

Answer 28

Generally, the smaller the molecules in a fraction, the more volatile and flammable the fraction.

Question 29

What are the reasons for cracking

Answer 29

1. Produces shorter chain alkanes which are higher in demand than longer chain alkanes. e.g. we need far more octane (petrol) than actually get from crude oil and we have more bitumen than we have use for.​ 2. Cracking also produces alkenes - used to make polymers and plastics

Question 30

What are the conditions for catalytic cracking

Answer 30

- temperature 600-700oC​ - Catalyst of silicon dioxide (SiO2, silica) or Aluminium Oxide (Al2O3, alumina)

Question 31

What is a polymer

Answer 31

POLYMERS are long chains of molecules consisting of small repeating units called MONOMERS.​ The monomers are often ALKENES

Question 32

What is a monomer

Answer 32

MONOMERS are small molecules that join together to make polymers

Question 33

What is polymerisation

Answer 33

POLYMERISATION = the formation of long chain molecules from lots of small molecules joining together