Alkanes

Question 1

Physical Properties of alkanes

Answer 1

• weak vdw
• as it gets longer bp increases
~ more vdw
• branching has lower bp
~ less surface contact
• insoluble in water
~ water is polar
~ non polar don’t dissolve well

Question 2

Reactivity

Answer 2

Unreactive
C-C is strong

Question 3

Describe process of Fractional distillation

Answer 3

• Crude oil is heated to vaporise
• Vapour passed in tower
• Which is cooler at top than bottom
• Fractions with low bp/ smallest molecules at top/
fractions separated by bp

Question 4

Alkanes and saturated

Answer 4

Alkanes are saturated
• Single C-C bond

Question 5

What factors determine which fraction hydrocarbon separated into

Answer 5

• Bp
• number of C atoms
• strength of vdw
• size/ length

Question 6

How does volatility determine position of fraction

Answer 6

• most volatile at top
• smallest chain has lowest bp
• thermal energy overcomes intermolecular forces

Question 7

How is nitrogen oxide formed in engine

Answer 7

• height temps when sparks I fnite fuel
• nitrogen reacts with oxygen

Question 8

How can sulfur and nitrogen form pollutants

Answer 8

• Nitrogen forms NO2 by reacting with O2
~ at high temps
• N2 + 2O2 —>

Question 9

What hydrocarbon are more likely to under go incomplete combustion

Answer 9

• longer chains
• Requires more oxygen to burn