Hydrocarbons

Question 1

What are hydrocarbons?

Answer 1

Any compound formed from carbon and hydrogen atoms only

Question 2

What is the general formula for alkanes?

Answer 2

CnH2n+2

Question 3

What are alkanes?

Answer 3

•alkanes are saturated hydrocarbons meaning each carbon atom forms four single covalent bonds
•the alkanes are a homologous series meaning they are a group of organic compounds that react in a similar way

Question 4

What are the first 4 alkanes?

Answer 4

Methane, ethane,propane and butane

Question 5

What is the formula for methane?

Answer 5

CH4

Question 6

What is the formula for ethane?

Answer 6

C2H6

Question 7

What is the formula for propane?

Answer 7

C3H8

Question 8

What is the formula for butane?

Answer 8

C4H10

Question 9

What impacts the properties of hydrocarbons?

Answer 9

The length of the carbon chain

Question 10

The shorter the carbon chain of a hydrocarbon the ……. it is

Answer 10

-less viscous (more runny)
-more volatile (lower boiling point)
-more flammable (easier to ignite)
•these properties make them good fuels

Question 11

Why are hydrocarbons with shorter carbon chains better as fuels?

Answer 11

They are easier to ignite/ are more flammable

Question 12

What reaction occurs during the complete combustion of hydrocarbons?

Answer 12

•hydrocarbon + oxygen—> carbon dioxide + water
•during this reaction both hydrogen and carbon from the hydrocarbon are oxidised

Question 13

What reaction occurs during the incomplete combustion of hydrocarbons?

Answer 13

Hydrocarbon+oxygen—> carbon monoxide + water + carbon

Question 14

When does complete combustion occur?

Answer 14

When there is a good supply of oxygen

Question 15

When does incomplete combustion occur?

Answer 15

When there is a poor supply of oxygen

Question 16

Why are hydrocarbons used as fuels?

Answer 16

They are used as fuels due to the amount of energy released when they combust completely

Question 17

Give an example of how the properties of hydrocarbons impact how they’re used for fuels?

Answer 17

Short chain hydrocarbons with lower boiling points are used as bottled gases- stored under pressure as liquids in bottles

Question 18

Why are long chain carbon hydrocarbons not as good fuels?

Answer 18

They form viscous (gloopy) liquids like tar which aren’t as useful

Question 19

Write a balanced equation for the complete combustion of methane (CH4)

Answer 19

CH4 + 2O2 —> CO2 + 2H2O

Question 20

Why do hydrocarbons with longer chains have higher boiling points and melting points.

Answer 20

They have strong intermolecular forces between them which take a lot of energy to overcome