alkanes

Question 1

describe trend in boiling point for straight chain alkanes

Answer 1

• as C chain increases, bp increases
• Mr increases
• so stronger vdW forces between molecules

Question 2

describe trend in boiling point for isomers of a specific alkene (branched isomers)

Answer 2

• as branching increases, bp decreases
• less surface area contact between molecules
  -weaker vdW forces between molecules

Question 3

why do compounds condense at different heights on fractionating column

Answer 3

different bps

Question 4

as carbon chain increases

Answer 4

• bp increases
• volatility decreases
• viscosity increases
• flammability decreases
• strength of vdW forces between molecules increases

Question 5

conditions and products of thermal cracking

Answer 5

-high temperature and high pressure
-produces alkenes and straight-chain alkanes

Question 6

conditions and products of catalytic cracking

Answer 6

-high temperature and moderate pressure
-zeolite catalyst
-produces aromatic hydrocarbons, branched alkanes and cycloalkanes

Question 7

commercial benefits of cracking?

Answer 7

-shorter chains in higher demand
-short chain alkanes used for fuel
-short chain alkenes used to produce polymers

Question 8

how can nitrous oxides and unburnt hydrocarbons be removed

Answer 8

using catalytic converter

Question 9

how can sulfur dioxide be removed

Answer 9

flue gas desulfurisation with CaO

Question 10

describe formation, problem caused by and how to reduce CO emissions

Answer 10

• formed during incomplete combustion
• problem: toxic
• solution: use catalytic converter

Question 11

describe formation, problem caused by and how to reduce C emissions

Answer 11

• formed during incomplete combustion
• problem: respiratory problems
• solution: ensure good supply of oxygen when burning fuels

Question 12

describe formation, problem caused by and how to reduce unburnt hydrocarbons emissions

Answer 12

• not burnt during combustion
• problem: photochemical smog
• solution: use catalytic converter

Question 13

describe formation, problem caused by and how to reduce nitrous oxide emissions

Answer 13

-combustion of N₂ and O₂ in the air at very high temperatures found in engines
-problem: reacts with water to form acid rain
-solution: use catalytic converter

Question 14

describe formation, problem caused by and how to reduce sulfur dioxide emissions

Answer 14

• combustion of fuels with sulfur-containing impurities
  -problem: reacts with water to form acid rain
  -solution: flue-gas desulfurisation

Question 15

equation for flue-gas desulfurisation

Answer 15

CaO + SO₂ → CaSO₃

Question 16

what does CaO act as in flue-gas desulfurisation?

Answer 16

base

Question 17

equation for reaction of N₂ with air at very high temperatures

Answer 17

N₂ + O₂ → 2NO

Question 18

describe features of a catalytic converter

Answer 18

• honeycomb structure; large surface area
• made of ceramic; withstands high temp and cheap
  -coated in Pt catalyst; increases surface area, reduces cost

Question 19

describe reaction happening in catalytic converter and give equation

Answer 19

-harmful pollutant gases react together to form less harmful gases
CO + NO → 1/2N₂ + CO₂