Organic Chemistry

Question 1

Hydrocarbons are……

Answer 1

Hydrocarbons are organic molecules made up only Hydrogens and carbons atom

Question 2

Alkanes are a …….

Answer 2

Alkanes are a type of hydrocarbons where all the carbon atoms are bonded by single bonds.

Question 3

What is the rule for the formula of alkanes

Answer 3

Question 4

Alkanes are saturated what does this mean

Answer 4

they contain single bonds

Question 5

What are the first four alkanes

Answer 5

Methane
Ethane
Propane
Butane

Question 6

The shorter the carbon chain …

Answer 6

The more runny the hydrocarbon is
Less viscous
More volatile - they have power boiling points
More flammable
They are also stored under pressure as liquide in bottles

Question 7

What is the equation for complete combustion

Answer 7

Hydrocarbon + oxygen -> carbon dioxide + water (+energy)

Question 8

What happens to the hydrocarbon and Carbon during the combustion

Answer 8

Oxidises

Question 9

How is crude oil made

Answer 9

Crude oil is a fossil fuel. Made of remains of plants and animals mainly PLANKTON.

Question 10

what conditions allow the crude oil to be formed in the ground

Answer 10

High temperature and pressure

Question 11

What is crude oil made of ?

Answer 11

Lots of different hydrocarbons most of which are alkanes

Question 12

How are different compounds in crude oil separated

Answer 12

Fractional distillation

Question 13

How does fractional distillation work ?

Answer 13

The oil is heated until most of it is turned into gas. The gas enter a fractioning column.
There is a temperature gradient in the column ( it’s hot at the bottom and cold at the top)
Longer hydrocarbons have higher boiling points. They condense back to liquids and drain out of the column early on when they’re near the bottom.
Shorter hydrocarbons have lower boiling points meaning they condense and drain out much earlier on - near to the top of the column where it is cooler
You end up with the crude oil mixture in different fractions. Which all contain the similar amount of Carbons so have similar boiling points in each fraction

Question 14

What various uses does crude oil have

Answer 14

Fuel for Most modern transport
Feedstock to make new compounds for use in things like polymers, solvents, lubricants and detergents

Question 15

What does cracking mean

Answer 15

Splitting up Long chains hydrocarbons

Question 16

Why are shorter hydrocarbons in demand

Answer 16

They are more flammable so make good fuels

Question 17

What is cracking

Answer 17

Cracking is thermal decomposition reaction- breaking molecules by heating them

Question 18

How does cracking work

Answer 18

Heat the long chain of hydrocarbons to vaporise them.
Then the vapour is passed over a hot powdered aluminium oxide catalyst
The long chain molecules split apart on the surface of the Specks of catalyst - this is catalytic cracking

Question 19

Alkanes are hydrocarbons which …

Answer 19

… have a double bond between two of the carbon atoms in their chain. They also contain the same amount of carbons making them unsaturated

Question 20

What are the first four alkenes

Answer 20

Ethene
Propene
Butene
Pentene

Question 21

What is the general formula for alkenes

Answer 21

C(n) H(2n)

Question 22

In a large amount of Oxygen alkenes …

Answer 22

Combust completely to produce only water and carbon dioxide. Alkenes burn with a smoky flame

Question 23

What happens when not enough Oxygen is present in a flame

Answer 23

They undergo incomplete combustion. Carbon dioxide and water is still produces but you can also get carbon and carbon monoxide which is a poisonous gas

Question 24

What is the equation for incomplete combustion

Answer 24

Alkene +oxygen -> carbon + carbon monoxide + carbon dioxide + carbon

Question 25

What are the results of incomplete combustion?

Answer 25

Yellow smoky flame and lessEnergy being released compared to complete combustion

Question 26

What happens when alkenes react with steam

Answer 26

Watet is added across the Double bond and alcohol is formed