Organic Chemistry

Combustion

Incomplete vs complete combustion

 

Complete combustion

Incomplete combustion

What is it?

When fuels react with oxygen to release useful energy.

When fuels react with a poor supply to release useful energy.

Word equation

Hydrocarbon + Oxygen ⇒ Carbon Dioxide + water

Hydrocarbon + Oxygen ⇒ Carbon Monoxide + carbon + water

Why is it a problem?

They release carbon dioxide which is bad for the environment.

They release carbon monoxide which is poisonous. The soot is also bad for our lungs.

Flame colour

Blue

Yellow

Bunsen air hole open or closed?

Open

Closed

 

Energy transferred

This is the amount of energy released minus the amount of energy absorbed.

 

Fuel efficiency

This is the amount of energy units transferred per mass unit in a fuel.

The most common fuel efficiency unit is Kj/mol

To calculate it do: Energy in kilojoules / Mass in moles

 

Hydrocarbons

Prefixes

 

# carbon atoms

prefix

1

Meth-

2

Eth-

3

Prop-

4

But-

5

Pent-

6

Hex-

 

Types of Hydrocarbons

 

Class

Distinguishing

feature

General formula

Structure

Name structure

Example

Alkane

Every Carbon atom is bonded to at least two hydrogen atoms

CnH2n+2

 

Prefix + ane

Ethane

Alkene

Has a double bond

CnH2n

 

Prefix + ene

Ethene

Alcohol

Has an O-H

CnH2n+1O

 

Prefix +anol

Ethanol

Carboxylic Acid

Has a double bonded oxygen and an O-H

CnH2nO2

 

Prefix + anoic acid

Ethanoic acid

Ester

Formed by combining an alcohol and a carboxylic acid. So has two carbon chains. Also has -C-O-C-

CnH2nO2

 

Prefix (alcohol) +yl + Prefix(cooh) + anoate

Ethyl Ethanoate

 

Test for alkenes

To test for an alkene, add a few drops of bromine.

Positive:

Negative:

 

Fractional distillation

Boiling points vs Hydrocarbon length

 

How fractional distillation works

  1. Crude oil ( a mixture of hydrocarbons) enters the furnace and is heated to around 350°C.
  2. The heated mixture enters the fractionating column
  3. All but one hydrocarbon boils at this temperature, so they rise up the fractionating column, leaving behind bitumen. ( A material used to make roads)
  4. As the mixture of hydrocarbons cools, one by one the boiling points of the hydrocarbons are reached and they begin condensing.
  5. When The hydrocarbons condense they are separated form the mixture and the liquid is siphoned off.
  6. The mixture of gases continues to rise until only the hydrocarbons which are gases at room temperature are left.
  7. The gases left are natural gases.

Biofuel

 

Advantages:

 

Disadvantages:

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