C7 - Organic chemistry

Question 1

What is a hydrocarbon?

Answer 1

. Is any compound that is formed from CARBON AND HYDROGEN ATOMS ONLY

Question 2

What are alkanes and what type of bond do they have?

Answer 2

. Are saturated compounds

. each carbon atom forms 4 single COVALENT bonds

Question 3

What is the general formula for alkanes

Answer 3

(Cn x H2n+2)

Question 4

What are the first 4 alkanes

Answer 4

. Methane (CH4)
. Ethane (C2H6)
. Propane (C3H8)
. Butane (C4H10)

Question 5

Properties of hydrocarbons as the chain gets longer

Answer 5

. The shorter the carbon chain, the less viscosity it has
. Short carbon chain hydrocarbons are more volatile (low boiling points)
. The shorter the chain the more flammable it is

Question 6

What is combustion

Answer 6

. Is when fuels combine with oxygen to release energy

Question 7

How are crude oils formed

Answer 7

Formed from remains of plants and animals, mainly plankton that died millions of years ago and were buried in mud and over millions of years with high temp and pressure remains turn to crude oil

Question 8

What is viscosity

Answer 8

How much a substance resists flowing

Question 9

What is crude oil

Answer 9

A mixture mainly made up of hydrocarbons

Question 10

What is fractional distillation

Answer 10

The process of separation in crude oil into fractions

Question 11

What is complete combustion

Answer 11

It occurs when there is plenty of oxygen

Question 12

What is incomplete combustion

Answer 12

Occurs when supply of air is limited

Question 13

How does fractional distillation work

Answer 13

1) oil is heated until most if it has changed to a gas. The gases then enter a fractionating column
2) in the column there is a concentration gradient
3. Long hydrocarbons have high boiling points so they condense back into a liquid and are drained out near the bottom . The shorter molecules have lower boiling points so they condense and drain out later on near the top, where it’s cooler
4) you end up with crude oil separated out into different fractions which contain a mixture of hydrocarbons that all contain a similar number of carbon atoms and have similar boiling points

Question 14

Uses of crude oil (2)

Answer 14

. Fuel for modern transport
. Petrochemical industry use crude oil as feedstock to make new compounds e.g polymers, solvents, lubricants and detergents

Question 15

What does cracking mean

Answer 15

Means splitting up long-chain Hydrocarbons

Question 16

The process of catalyst cracking (1 method of cracking)

Answer 16

1) heat the long-chain hydrocarbon to vaporise them
2) the vapour is then passed over a hot powered aluminium oxide catalyst
3) long chain molecules then split apart on the surface of the specks of the catalyst ( this is catalyst cracking)

Question 17

What is a covalent bond

Answer 17

Is the bond between 2 atoms that share two or more pairs of electrons