Introduction to Organic Chemistry

Question 1

What is crude oil, in terms of its formation?

Answer 1

Crude oil is the remains of an ancient biomass consisting mainly of plankton that was buried in mud

Question 2

What are most of the compounds in crude oil?

Answer 2

Hydrocarbons (molecules made up of hydrogen and carbon atoms only)

Question 3

Where is crude oil found?

Answer 3

In rocks

Question 4

What is the general formula for the homologous series of alkanes?

Answer 4

CnH2n+2

Question 5

What are properties of Hydrocarbons?

Answer 5

• Some properties depend on the size of their molecules, e.g. boiling point, viscosity and flammability. These properties influence how hydrocarbons are used as fuels

Question 6

How does the length of the fraction affect the viscosity?

Answer 6

The longer the fraction, the more viscous the fraction will be

Question 7

How does the length of the fraction affect the volatility?

Answer 7

Shorter fractions have lower boiling points and so evaporate more easily. The more volatile a fraction is, the easier it mixes with air. This means the fraction ignites and burns more easily

Question 8

Fractional Distillation

Answer 8

In fractional distillation, crude oil is evaporated. The fractionating column is hotter at the bottom and colder at the top. Different fractions have different boiling points and so condense at different levels. Longer fractions collect at the bottom, shorter fractions collect at the top

Question 9

How does the length of the fraction affect the boiling point?

Answer 9

The longer the chain, the higher the boiling point

Question 10

Properties of longer chain hydrocarbons

Answer 10

Higher boiling points- as the longer molecules entangle more and are harder to separate and so have STRONG INTERMOLECULAR FORCES, which take a lot of energy to separate
Lower volatility (turn to a gas less easily)- STRONG INTERMOLECULAR FORCES holding the molecules together
High viscosity (as the molecules entangle and have STRONG INTERMOLECULAR FORCES)
Lower flammability

Question 11

What number of carbons do refinery gases have?

Answer 11

1 - 4

Question 12

What number of carbons do gasoline / petrol have?

Answer 12

5 - 10

Question 13

What number of carbons does kerosene have?

Answer 13

11 - 15

Question 14

What number of carbons does diesel have?

Answer 14

16 - 20

Question 15

How many carbons does residue have?

Answer 15

20 +

Question 16

Uses of refinery gas

Answer 16

Used as fuel for heating, cooking and as a chemical feedstock

Question 17

Uses of gasoline / petrol

Answer 17

Used as fuel for cars, chemical feedstock

Question 18

Uses of kerosene

Answer 18

Used as aircraft fuel and turned into detergents

Question 19

Uses of diesel

Answer 19

Fuel for diesel engines and boiler fuel

Question 20

Uses of residue

Answer 20

Used in making roads and flat roofs, also used to make lubricants, wax

Question 21

When does complete combustion occur?

Answer 21

When a substance burns in excess oxygen

Question 22

What happens during complete combustion?

Answer 22

• All the carbon in the substance join together with oxygen to form carbon dioxide
• All of the hydrogen in the substance joins together with oxygen to form water
• (any other elements present will also combine with oxygen to form other oxides)

Question 23

What are the two tests for water?

Answer 23

• Anhydrous copper sulphate
• Cobalt chloride paper

Question 24

Test for water: Anhydrous copper sulphate

Answer 24

Anhydrous copper sulphate is a white/grey solid that has a very clear reaction with water. It turns blue and gets hot, both of which are classic signs of a chemical reaction

Question 25

Test for water: Cobalt chloride paper

Answer 25

This is a special test paper which has to be kept dry When it is dry it is pale blue, but if dipped into water it turns white, often with a slightly pink colour at the boundary between the two colours

Question 26

Test for carbon dioxide

Answer 26

If we take the hot gases from the flame and bubble them through limewater we see the limewater turn milky - which is the classic test for CO2

Question 27

When does incomplete combustion occur?

Answer 27

When something burns in a reduced supply of oxygen

Question 28

Incomplete combustion

Answer 28

- There isn't enough oxygen to turn all the carbon atoms into CO2 and so some of the carbon atoms turn into carbon monoxide, CO or just end up as carbon, C - All the hydrogen atoms in the substance though still end up as water, CO2

Question 29

What is carbon monoxide?

Answer 29

A dangerous, colourless, odourless gas that can kill in high concentrations

Question 30

Why is carbon monoxide dangerous?

Answer 30

It can bond very strongly to the haemoglobin in the blood and stop that haemoglobin molecule from being able to transport oxygen around the body. If you breathe in enough CO then it will bond to too much of the haemoglobin in your body and you will suffocate

Question 31

How can CO poisoning be prevented?

Answer 31

Service the boiler in your house once a year to make sure that all the air vents into the boiler are clear of blockages so oxygen can get freely to it. Some people also have CO sensors near a boiler, especially if the boiler is in an attic bedroom

Question 32

Why is incomplete combustion easy to see?

Answer 32

You always end up with some carbon (as soot) in the flame and this will always make the flame appear yellow

Question 33

What setting on the Bunsen burner is incomplete combustion?

Answer 33

The yellow 'safety flame' as we close the air hole at the base of the Bunsen and restrict the flow of oxygen into the flame

Question 34

Why do we never heat our glassware with the yellow flame?

Answer 34

It will leave a grimy black deposit of soot on our test tubes

Question 35

What are the rules for writing complete combustion equations?

Answer 35

- All the carbon atoms in the hydrocarbon fuel turn into carbon dioxide molecules - All the hydrogen atoms in the fuel turn into water - Finally we can use how many atoms of oxygen there are in our product molecules to see how many molecules of oxygen, O2, we need to balance the equation

Question 36

What are the rules for writing incomplete combustion equations?

Answer 36

- All the hydrogen atoms in the fuel turn into water - The carbon atoms on the left hand side of the equation turn into some CO2, some CO and some C. There can be any mixture of these three normally, but the total number of carbon atoms on the left and right hand side must be the same - Finally we can use how many atoms of oxygen there are in our product molecules to see how many molecules of oxygen, O2, we need to balance the equation

Question 37

What is the general equation for alkenes

Answer 37

CnH2n

Question 38

Properties of longer hydrocarbons

Answer 38

- Have higher boiling points - Are less volatile - Are less flammable - Are more viscous - Have a darker colour

Question 39

Properties of shorter hydrocarbons

Answer 39

- Have lower boiling points - Are volatile - Are flammable - Are less viscous - Are either colourless or pale in colour