Topic 5- Introduction to Organic Chemistry and Alkanes

Question 1

Define a homologous series

Answer 1

A group of organic compounds that have the same functional group, but each successive member differs by CH2.

Question 2

Characteristics of a homologous series

Answer 2

• Each member has the same functional group
• Each member has the same general formula
• Each member has similar chemical properties

Question 2

Characteristics of a homologous series

Answer 2

• Each member has the same functional group
• Each member has the same general formula
• Each member has similar chemical properties

Question 3

How are alkanes saturated hydrocarbons?

Answer 3

They are compounds containing only hydrogen and carbon atoms.

Question 4

Define Structural Isomerism

What are the 3 types?

Answer 4

Compounds that have the same molecular formula but a different structural formula.
- Chain
- Position
- Functional group

Question 5

Chain Isomers

Answer 5

When there is more than one way of arranging the carbon chain of a molecule.

Question 6

Position Isomers

Answer 6

Have the same carbon chain but the functional group is bonded to different carbons.

Question 7

Functional group isomers

Answer 7

Have the same molecular formula but have different functional groups.

Question 8

Stereoisomers

Answer 8

Have the same structural and molecular formula, but a different arrangement of atoms in space.

Question 9

What leads to E-Z isomerism?

Answer 9

The restricted rotation about a planar carbon carbon double bond.

Question 10

What`s the criteria for E-Z isomerism?

Answer 10

• A carbon carbon double bond must be present
• Each carbon atom must be attached to two different groups

Question 11

Describe Z-isomers

Answer 11

When the highest priority groups are on the same side of the double bond (together).

Question 12

Describe E-isomers

Answer 12

When the highest priority groups are on different sides of the double bond (opposite).

Question 13

Describe fractional distillation

Answer 13

A process in which a mixture of liquids is separated into groups of compounds with similar boiling points.

Question 14

How do the alkanes separate in the fractionating column?

Answer 14

-As vapor is passed into the fractionating column it moves up the column and gets cooler.
- Owing to the different chain lengths and boiling points of the different hydrocarbon, each fraction condenses at different temperatures.

Question 15

What is cracking?

Answer 15

The breakdown of large alkanes into smaller, more useful molecules by breaking the C-C bonds.
Requires high temperatures to break the strong C-C bonds.

Question 16

Catalytic cracking

Answer 16

• High temperature (450 degrees)
• Slight pressure
• Zeolite catalyst
• Produces motor fuels and aromatic hydrocarbons

Question 17

Thermal cracking

Answer 17

• High temperature (1000 degrees)
• High pressure
• No catalyst
• Produces high percentage of alkenes (useful to make polymers)

Question 18

Complete combustion

Answer 18

Occurs in a plentiful supply of air and produces carbon dioxide and water.

Question 19

Incomplete combustion

Answer 19

Occurs when there is a limited supply of air. The reaction produces carbon monoxide, water and sometimes soot.

Question 20

How is carbon monoxide produced in the internal combustion engine?
How is it a pollutant?

Answer 20

• Incomplete combustion of the fuel in limited oxygen.
• Binds to hemoglobin instead of oxygen.

Question 21

How are hydrocarbons produced in the internal combustion engine?
How is it a pollutant?

Answer 21

• Not all of the fuel burns, and some unburnt hydrocarbons leave the exhaust.
• Hydrocarbons react with oxides of nitrogen (NOx) to form ground level ozone, which is a component of smog.

Question 22

How are Oxides of Nitrogen produced in the internal combustion engine?
How is it a pollutant?

Answer 22

• Nitrogen from the air reacts oxygen at high temperature and pressure in the engine.
• Oxides of nitrogen react with unburnt hydrocarbons to produce photochemical smog. Oxides of nitrogen dissolve in water to form acid rain.

Question 23

How is Carbon produced in the internal combustion engine?
How is it a pollutant?

Answer 23

• Incomplete combustion of the fuel in very limited oxygen.
• Carbon particles exacerbate asthma.

Question 24

Catalytic converters

Answer 24

• Part of exhausts which remove gaseous pollutants.
• Has a honeycomb ceramic structure that is coated with a metal catalyst such as platinum or rhodium.
• Coating means less metal = lower cost
• Honeycomb means large SA for fast reaction

Question 25

• Equation for removal of CO
• Equation for removal of Unburnt Hydrocarbons
• Equation for Oxides of nitrogen

Answer 25

• CO + NO –> CO2 + 1/2 N2
• Unburnt hydrocarbons react with nitrogen monoxide to produce nitrogen, carbon dioxide and water
• Oxides of nitrogen reduced to N2 or O2
  2NO–> N2 + O2

Question 26

Problems with Sulfur

Answer 26

Some hydrocarbons contain sulfur as an impurity. When sulfur burn it produces a toxic gas, sulfur dioxide.
Sulfur dioxide can cause respiratory problems and react with oxygen and water to produce acid rain.

Question 27

Acid rain

Answer 27

-Pollutes the environment by killing vegetation, corroding buildings and killing fish in rivers and lakes.

Question 28

How is Sulfur removed from flue gases?

Answer 28

• Using calcium oxide or calcium carbonate in a neutralization reaction :
  CaO + SO2 –> CaSO3
  CaCO3 + SO2 –> CaSO3 + CO2
• CaSO3 is oxidized to CaSO4 which is used as a construction material.