Organic Chemistry Part 1

Question 1

What is a hydrocarbon?

Answer 1

• molecules made of hydrogen and carbon atoms only

Question 2

What is crude oil?

Answer 2

• a finite resource found in rocks
• remains of ancient biomass (mianly plankton buried in mud)
• mixture of compounds- mostly hydrocarbons

Question 3

What is crude oil processed to make?

Answer 3

• fuels
• feedstocks

Question 4

What are feedstocks?

Answer 4

• raw material for the petrochemical industry
• mode into solvents, lubricants, polymers, detergents

Question 5

Describe fractional distillation

Answer 5

• crude oil heated, evaporated
• vapour enters fractionating column (hot at bottom, cool at top)
• molecules rise until they have cooled enough to condense
• crude oil separated into different fractions with different boiling points

Question 6

What is the realationship between the size of the molecules and where they condense on the fractionating column?

Answer 6

• longer molecules = condense lower (hotter) in tower
• smaller molecules = condense higher (cooler) in tower

Question 7

How does the carbon chain length affect the molecules’ properties?

Answer 7

• longer chain = higher boiling point
• longer chain = more viscous
• longer chain = less flammable

Question 8

What is the general formula for an alkane?

Answer 8

Cn H2n+2

Question 9

What are the names and formulas of the first four alkanes?

Answer 9

1) methane CH4
2) ethane C2H6
3) propane C3H8
4) butane C4H10

Question 10

Name the fractions of crude oil from top to bottom

Answer 10

• liquefied petrolium gases (fuels)
• petrol (fuel for cars)
• kerosene (aircraft fuel)
• diesel (fuel for cars, buses, and lorries)
• heavy fuel oil (fuel for ships or power stations)

Question 11

What type of reaction is combustion with hydrocarbons?

Answer 11

• oxidation
• hydrogen and carbon gain oxygen, oxidised

Question 12

What is the formula of the complete combustion of a hydrocarbon?

Answer 12

hydrocarbon + oxygen -> carbon dioxide + water

Question 13

What is cracking?

Answer 13

• breaking down long chain alkanes to produce smaller, more useful molecules

Question 14

Why is cracking important?

Answer 14

• long hydrocarbons have less demand, would be wasted otherwise
• shorter chain molecules have more demand
• alkenes used as feedstock for making polymers

Question 15

What does cracking do?

in terms of bonds

Answer 15

• break covalent bonds and forms new bonds

Question 16

What happens during catalytic cracking?

Answer 16

• long chain alkanes heated and vaporised
• vapour passed over hot catalyst

450-550 C

Question 17

What happens during steam cracking?

Answer 17

• long chian alkanes heated and vaporised
• vapour mixed with steam
• heated to very high temperature

750-900 C, high pressure

Question 18

What is the difference between an alkane and an alkene?

Answer 18

• alkanes only have single bonds
• alkenes have double bonds

Question 19

Draw and label a diagram of cracking in a lab

Question 20

What is the general formula for alkenes?

Answer 20

• CnH2n

Question 21

How do you test for alkenes?

Answer 21

• add few drops of bromine water to alkene
• add stopper and shake
• alkane = no change
• alkene = orange-brown to colourless
• alkenes are more reactive than alkanes