C7 Organic chemistry

Question 1

What is crude oil made from ?

Answer 1

Crude oil is made of organisms (ancient biomass) that lived and died millions of years ago – mainly plankton that was buried in mud.

Question 2

Crude oil is finite, what does finite mean ?

Answer 2

Finite means that when it is used up it takes millions of years to be replaced.

Question 3

What is a hydrocarbon ?

Answer 3

A compound made from hydrogen and Carbon only.

Question 4

What is the general formula of an alkane.

Answer 4

The general formula for the homologous series of alkanes

is CnH2n+2

Question 5

Draw the displayed formula for methane.

Answer 5

See diagram

Question 6

What is the formula for butane

Answer 6

C₄H₁₀

Question 7

What are the names of the 1st 4 alkanes ?

Answer 7

methane, ethane, propane and butane.

Question 8

The many hydrocarbons in crude oil may be separated into fractions, by which process ?

Answer 8

Fractional distillation

Question 9

The many hydrocarbons in crude oil may be separated into fractions, what do the fractions have in common ?.

Answer 9

Each fraction contains molecules with a similar number of carbon atoms,

Question 10

What useful materials can the fractions be processed into ?

Answer 10

The fractions can be processed to produce fuels and feedstock for the petrochemical industry.

Question 11

Name 4 fuels which can be produced from crude oil ?

Answer 11

Many of the fuels on which we depend for our modern lifestyle, such as petrol, diesel oil, kerosene, heavy fuel oil and liquefied

petroleum gases, are produced from crude oil.

Question 12

Explain how fractional distillation works

in terms of evaporation and condensation.

Answer 12

• The crude oil enters a tall fractioning column, which is hot at the bottom and cooler at the top.
• The crude oil gets heated till the boiling point of the 1st fraction is reached.
• The temperature remains constant until that fraction has evaporated.
• The fraction once evaporated comes off as a gas and is then cooled down (condensed) and collected as a liquid.
• This process continues until all the fractions have been collected.

Question 13

What is it about a hydrocarbon that affects it’s boiling point ?

Answer 13

The chain length

Question 14

How is energy released from fuels ?

Answer 14

The combustion of hydrocarbon fuels releases energy.

Question 15

What are the products of combustion ?

Answer 15

During combustion, the carbon and hydrogen in the fuels are oxidised. The complete combustion of a hydrocarbon produces carbon dioxide

and water.

Question 16

How does the boiling points , viscosity and m flammability of alkanes change as the chainlength increases ?

Answer 16

Boiling point, and viscosity increases asthe chainlength increases.
The flammability decreases as the chainlength of the alkanes is increased.

Question 17

Why are alkanes cracked ?

Answer 17

Hydrocarbons can be broken down (cracked) to produce smaller, more useful molecules.

Question 18

What are 2 methods used for cracking alkanes ?

Answer 18

Cracking can be done by various methods including catalytic cracking and steam cracking.

Question 19

What are the products of cracking alkanes ?

Answer 19

short chain

alkanes and/or alkenes.

Question 20

What is the test for an alkene ?

Answer 20

Alkenes are more reactive than alkanes and react with bromine water, which is used as a test for alkenes.

Question 21

When Bromine water is added to alkenes what observations are made.

Answer 21

The bromine water changes from orange to colourless.

Question 22

What are used to make Polymers ?

Answer 22

Alkenes are used to produce polymers and as starting materials for the production of many other chemicals.

Question 23

Write an equation for the cracking of C₁₆H₃₄

Answer 23

Any answer is correct as long as smaller alkanes are made and alkenes are in the product. The number of carbons and hydrogens must be the same on both sides of the equation.

Question 24

Higher tier

What is the general formulae for an alkene ?

Answer 24

Alkenes are hydrocarbons with a double carbon-carbon bond. The general formula for the homologous series of alkenes is CnH2n

Question 25

Higher tier only

What is an unsaturated molecule ?

Answer 25

Alkene molecules are unsaturated because they contain two fewer hydrogen atoms than the alkane with the same number of carbon

atoms.

Question 26

Higher tier only

What are the first 4 members of alkenes ?

Answer 26

The first four members of the homologous series of alkenes are ethene, propene, butene and pentene.

Question 27

Chemistry only

What is the functional group of an alkene

Answer 27

Alkenes are hydrocarbons with the functional group C=C.

Question 28

In what way are alkenes similar and different to alkanes in their reactions with oxygen ?

Answer 28

Alkenes react with oxygen in combustion reactions in the same way as other hydrocarbons, but they tend to burn in air with smoky flames because of incomplete combustion.

Question 29

Chemistry tier

What happens when alkenes react with hydrogen ?

Answer 29

They make alkenes

Question 30

Chemistry tier

What happens when alkenes react with hydrogen halides ?

Answer 30

They make halogenoalkanes.

Question 31

Chemistry tier

What happens when alkenes react with water ?

Answer 31

They make alcohols.

Question 32

Chemistry tier

Write an equation for Ethene reacting with water.

Answer 32

C₂H₄ + H₂0 = C₂H₅ OH

Question 33

Chemistry tier

Write an equation for Ethene reacting with Hydrogen.

Answer 33

C₂H₄ + H₂ = C₂H₆

Question 34

Chemistry tier

Write an equation for Ethene reacting with Hydrogen Bromide.

Answer 34

C₂H₄ + HBr = C₂H₅ + Br

Question 35

Chemistry tier

What functional group do alcohols contain ?

Answer 35

Alcohols contain the functional group –OH.

Question 36

Chmistry tier

Write the formula for ethanol

Answer 36

Alcohols can be represented in the following forms:

CH₃CH₂OH

Question 37

Chemistry tier

Write an equation for ethanol reacting with sodium

Answer 37

C₂H₅0H + Na= C₂H₅0Na

Question 38

How is alcohol formed using enzymes ?

Answer 38

Aqueous solutions of ethanol are produced when sugar solutions are fermented using yeast.