Organic chemistry

Question 1

Define crude oil

Answer 1

The remains of an ancient biomass consisting mainly of plankton that was burried in mud

Question 2

What are most of the compounds in crude oil called?

Answer 2

Hydrocarbons

Question 3

Define hydrocarbons

Answer 3

Molecules made up of hydrogyn and carbon atoms only

Question 4

What are most of the hydrocarbons in crude oil called?

Answer 4

Alkanes

Question 5

What is the general formula for alkanes

Answer 5

C n H 2n+2

Question 6

What are the first four members of the alkanes called?

Answer 6

Methane, ethane, propane and brutane
My exquisite popcorn burnt

Question 7

What type of bond do alkanes have between the carbon atoms?

Answer 7

Single covalent bond

Question 8

State the formulas for all 4 alkanes

Answer 8

Methane - CH4
Ethane - C2H6
Propane - C3H8
Butane - C4H10

Question 9

What is fractional distillation used for in terms of crude oil?

Answer 9

The hydrocarbons in crude oil may be seperated into fractions, each of which contains molecules with a similar number of carbon atoms

Question 10

Give examples of the fuels produced from fractions

Answer 10

Petrol
Diesel oil
Kerosene
Heavy fuel oil
Liquefied petroleum gases

Question 11

Give examples of the useful materials in the petrochemical industry produced from fractions

Answer 11

Solvents
Lubricants
Polymers
Detergents

Question 12

Define viscosity

Answer 12

The thickness of a liquid

Question 13

How does the boiling point of hydrocarbons change with increasing molecular size?

Answer 13

The larger the size, the higher the boiling point

Question 14

How does the viscosity of hydrocarbons change with increasing molecular size?

Answer 14

The larger the size, the higher the viscosity

Question 15

How does the flammability of hydrocarbons change with increasing molecular size?

Answer 15

The larger the size, the less the flammability

Question 16

What does the complete combustion of a hydrocarbon produce?

Answer 16

Carbon dioxide and water

Question 17

Why are hydrocarbons cracked?

Answer 17

To produce smaller, more useful molecules

E.g. to make fuels as longer chains aren’t flammable

Question 18

Describe the conditions used for catalytic cracking

Answer 18

Uses high temperature
Uses a catalyst to speed up the reaction

Question 19

Describe the conditions used for steam cracking

Answer 19

Uses high temperature
Uses steam

Question 20

Define alkene

Answer 20

A hydrocarbon which is a product of cracking

Question 21

Compare alkanes with alkenes

Answer 21

Alkanes have a single covalent bond between 2 carbon atoms whereas alkenes of a double covalent bond

Alkenes are more reactive than alkanes

Question 22

Describe the test for alkenes

Answer 22

Alkenes react with bromine water and turn colourless to indicate the presence of alkenes

Question 23

Explain the usefulness of cracking

Answer 23

There is a high demand for fuels with small molecules and so some
of the products of cracking are useful as fuels

Question 24

What are alkenes used to do?

Answer 24

Chemicals called polymers
Used as the starting material for other useful chemicals

Question 25

Explain how fractional distillation works in terms of evaporation and condensation

Answer 25

The oil is heated in the fractionating column and the oil evaporates
and condenses at a number of different temperatures

The many hydrocarbons in crude oil can be separated into fractions
each of which contains molecules with a similar number of carbon
atoms

The fractionating column works continuously, heated crude oil is
piped in at the bottom. The vaporised oil evaporates and rises up the
column and the various fractions are constantly tapped off at the
different levels where they condense

Question 26

Alkanes have _________ bonds

Answer 26

single