ALKANES

Question 1

What are alkanes?

Answer 1

They are a homologous series
Family of hydrocarbons 
-same general formula
-similar chemical properties 
-show a trend in physical properties

Question 2

Alkanes are saturated (meaning)

Answer 2

Only have single ( c-c) bonds

Question 3

What is isomerism?

Answer 3

When more than one compound has the same chemical formula but different chemical structures (different arrangements of branches)

Question 4

What is the general formula for alkanes?

Answer 4

CnH2n+2

Question 5

What is a functional group?

Answer 5

An atom or a group of atoms that determine the chemical properties of a compound
Compounds in the same homologous series have the same functional group

Question 6

Name the organic compounds

Answer 6

Monkeys eat pink bananas

Methane=1 carbon
Ethane=2 
Propane=3
Butane=4
Pentane=5
Hexane=6

Question 7

Combustion of hydrocarbons - state what results?

Answer 7

Complete combustion

• water + carbon dioxide produced when alkanes burnt in plentiful supply of oxygen

Question 8

Burning alkanes investigation method

Answer 8

Set up the apparatus. Light the Bunsen burner so that the alkane can be burnt and the combustion products collected

Question 9

Burning alkanes set up

Answer 9

1. Inverted funnel over Bunsen burner
2. U tube connected to inverted funnel, u tube in ice bath (to condense the water vapour)
3. Cobalt chloride paper inside U tube
4. Delivery tube connected to u tube and a test tube
5. Limewater in test tube
6. Test tube connected to water pump (draw products through system)

Question 10

State the tests for water and carbon dioxide in your observations

Answer 10

— cobalt chloride paper turns from BLUE to PINK or anhydrous copper Sulfate turns from WHITE to BLUE
— small amount of colourless liquid collects in U tube
— Limewater turns cloudy

Question 11

Show the equation for complete combustion for methane

Answer 11

Methane + oxygen —> carbon dioxide + water

CH4 + 2o2 —> co2 + 2H2o

Question 12

Incomplete combustion

Answer 12

Limited oxygen supply can cause incomplete combustion,
Leads to formation of carbon (soot) or carbon monoxide gas instead of carbon dioxide
Dangerous because it binds to red blood cells and reduces the ability of blood to carry oxygen round the body

Question 13

Incomplete combustion equation with octane

Answer 13

Octane is a hydrocarbon present in gasoline/petrol
Octane + oxygen —> carbon monoxide + water

2C8H18 + 17O2 —> 16CO + 18H2O

Question 14

What happens in car engines?

Answer 14

Temp reached is high enough to allow nitrogen and oxygen from air to react, forming oxides of nitrogen