Section 3 Organic Chemistry

Question 0

What is the general formula for alkanes?

Answer 0

CnH2n+2

Question 1

Alkanes and alkenes are both ………..

Answer 1

Hydrocarbons

Question 2

What is complete combustion?

Answer 2

Happens when there’s plenty of oxygen

Produces carbon dioxide, water and lots of energy

Question 3

What is incomplete combustion?

Answer 3

Happens when there isn’t enough oxygen
Makes carbon, carbon monoxide, carbon dioxide and water
Also produces smokey yellow flame and less energy

Question 4

Halogens react with alkanes in ……… to make ………

Answer 4

Uv light

Halo alkanes

Question 5

What do alkenes have?

Answer 5

Carbon double bond

So they are unsaturated molecules (they can make more bonds)

Question 6

What is the general formula for alkenes?

Answer 6

CnH2n

Question 7

What do halogens react with alkenes to form?

Answer 7

Haloalkanes

Question 8

What is the reaction between alkenes and halogens?

Answer 8

Addition reactions

Question 9

How can ethanol be produced?

Answer 9

Reaction of Ethene and steam

Fermentation

Question 10

How can ethanol become Ethene?

Answer 10

Dehydration reaction (removing water)

Question 11

What is the reaction between halogens and alkanes?

Answer 11

Substitution reaction

Question 12

How can you test for carbon double bonds?

Answer 12

Shake an Alkene with orange bromine water 
The solution will become colourless 
Makes dibromoalkane (which is colourless)

Question 13

Explain how ethanol can be produced from ethene and steam

Answer 13

Reaction needs temp of 300 degrees C
Pressure of 60-70 atmospheres
Phosphoric acid catalyst 
Fairly cheap because no Ethene waste
Needs crude oil to make ethanol which is non renewable, so will become more expensive

Question 14

Explain how ethanol can be produced by fermentation?

Answer 14

Sugar e.g. glucose is converted into ethanol using yeast - very slow
Temp of 30 degrees C
Cheap Simple equipment
high labour costs
Uses raw materials that are renewable
Ethanol produced isn’t concentrated so needs to be distilled and purified

Question 15

How can ethanol be turned back to Ethene?

Answer 15

Dehydration reaction - remove the water

Ethanol vapour is passed over hot catalyst of aluminium oxide Catalyst provides large surface area for reaction

Question 16

Recall the products of complete and incomplete combustion of alkanes.

Answer 16

Complete (safe): carbon dioxide + water.

Incomplete (not safe): carbon + carbon monoxide + carbon dioxide + water.

Question 17

Describe the substitution reaction of methane with bromine to form bromomethane in the presence of UV light.

Answer 17

Bromine (halogen) replaces hydrogen atom to form bromomethane (a substitution reaction).

Question 18

What are the names of the first five alkanes?

Hint: Mice Eat Peanut Butter.

Answer 18

Methane
Ethane
Propane
Butane
Pentane

Question 19

What are the names of the first three alkenes?

Hint: Eggs, Pan, Boil.

Answer 19

Ethene
Propene
Butene.

Question 20

What is a homologous series?

Answer 20

A group of compounds that can all be represented by the same general formula.

Question 21

What is a hydrocarbon?

Answer 21

Molecules that are made up of hydrogen and carbon atoms only.

Question 22

What is a saturated general formula?

Answer 22

Saturated means something has bonded as many times as possible. General formula is the most simplified the ratio of molecules can be.

Question 23

What is the equation for incomplete combustion?

Answer 23

Alkane + oxygen ➡️ carbon + carbon dioxide + carbon monoxide + water (+ energy)

Question 24

What is the equation for complete combustion?

Answer 24

Alkane + oxygen ➡️ carbon dioxide + water (+ energy)

Question 25

What is a homologous series?

Answer 25

A group of compounds with the same general formula

Question 25

What are the names of the first five alkanes?

Answer 25

Methane
Ethane
Propane
Butane
Pentane

Question 25

What are the first 3 alkenes?

Answer 25

Ethene
Propene
Butene