Alkanes

Question 1

Are alkanes saturated and why

Answer 1

They are saturated because they only contain single bonds

Question 2

How does boiling point of straight-chain alkanes change as the chain gets longer

Answer 2

Boiling point increases

Question 3

Why does boiling point of straight chain alkanes increase as chain length increases

Answer 3

As length increases the surface area of molecules in contact with other molecules increases meaning van der waals forces are stronger between molecules so require more energy to overcome

Question 4

Why do branched-chain alkanes have lower boiling points than straight chain alkanes

Answer 4

Because they cannot pack as closely together meaning there are fewer points of contact between molecules so van der waals forces between molecules are weaker and require less energy to overcome

Question 5

What is complete combustion and what does it produce

Answer 5

Burning of hydrocarbon in excess oxygen and produces carbon dioxide and water

Question 6

What type of reaction is complete combustion of alkanes

Answer 6

Highly exothermic making them good fuels as they release a large amount of energy

Question 7

What is incomplete combustion and what does it produce

Answer 7

Burning of hydrocarbon with limited oxygen producing carbon monoxide/soot and water

Question 8

What colour flame does complete combustion produce

Answer 8

Blue

Question 9

What colour flame does incomplete combustion produce

Answer 9

Orange smoky flame

Question 10

What is a risk particularly associated with alkanes

Answer 10

Flammable