alkanes+haloalkanes(p2)

Question 1

what is fractional distillation?

Answer 1

a method of separating crude oil fractions using their boiling points

Question 2

describe how crude oil separates in the fractioning column

Answer 2

1. vaporised at 350 degrees
2. passes into fractioning column using temperature gradient
3. as they pass up they condense +cool
   highest temprature at the bottom, lowest at the top

Question 3

what occurs at the top and bottom of the fractioning column?

Answer 3

lowest BP dont condense so are drawn out as gases at the top. larger hydrocarbons dont vaporise so stay at bottom as residue

Question 4

what are the two types of cracking?

Answer 4

catalytic+steam(thermal)

Question 5

what are the conditions of catalytic cracking?

Answer 5

zeolite catalyst
500 degrees

Question 6

what does catalytic cracking produce?

Answer 6

aromatic hydrocarbons+alkanes

Question 7

what are the conditions of steam cracking?

Answer 7

up to 1000 degrees, 70 atmospheres

Question 8

what does steam cracking produce?

Answer 8

alkenes

Question 9

what is a free radical?

Answer 9

a particle with an unpaired electron

Question 10

give the mechanism of a free radical substitution between a chlorine free radical and methane to make a haloalkane

Question 11

give the complete combustion equation of propane

Answer 11

C3H8+502=4H20+3CO2

Question 12

give the incomplete combustion equation for propane

Answer 12

C3H8+31/2=3CO=4H20

Question 13

What is ozone?

Answer 13

a chemical sunscreen, absorbs UV radiation from the sun, which can cayse sunburn/skin cancer

Question 14

give the free radical mechanism of ozone formation

Question 15

what is a problem chloroflourocarbons(CFCs) in our atmosphere?

Answer 15

destroys ozone as chlorine free radicals can form

Question 16

give the free radical mechanism for the destruction of ozone

Question 17

why is nitrogen monoxide dangerous and how is it formed?

Answer 17

it is produced when high pressure and high temperature in a car engine cause nitrogen and oxygen in the air to react with each other= toxic,poisonous

Question 18

give the reaction of nitrogen monoxide reacting further to form nitrogen dioxide

Answer 18

N2+O2=2NO
2NO+O2=2NO2

Question 19

why are nitrogen oxides especially dangerous with hydrocarbons?

Answer 19

as all fuel isnt burnt, when these two react it forms gorund level ozone which can irritate eyes,aggravate respiratory problems

Question 20

what is the purpose of a catalytic converter?

Answer 20

remove nitrogen oxides, unburnt hydrocarbons, carbon monoxide from exhausts

Question 21

when burnt why are fossil fuels particulary dangerous?

Answer 21

they contain sulfur so when burnt it forms sulfur dioxide and if this in the atmopsher it can dissolve and is converted to sulfuric acid which can lead to acid rain, this is the same with NO2

Question 22

how can sulfur dioxide be removed from flue gases?

Answer 22

powdered calcium carbonate mixed with water=used as they neutralise sulfur dioxide. it is then sprayed in SO2 gas

Question 23

give the reaction between sulfur dioxide and calcium carbonate

Answer 23

CaO+SO2=CaSO3

Question 24

how do you make a haloalkane?

Answer 24

alkane+halogen in a free radical substitution

Question 25

give the equation for the incomplete combustion of butane forming soot

Answer 25

C4H10=2.5O2–> 4C+5H2O

Question 26

how does CO2 contribute to global warming?

Answer 26

CO2 absorbs infra red radiation from sun and emits some of it back to earth (greenhouse effect) in turn increasing global temperature

Question 27

what is the BP trend going down haloalkanes?

Answer 27

BP increase as stregnth of van der waals increase as size of molecule increases. require more energy to overcome

Question 28

what are the reactivity of haloalkanes?

Answer 28

stronger the bond enthalpy, the less reactive. so going down the group the more reactive

Question 29

how do chlorofluorocarbons break down ozone?

Answer 29

C-Cl bonds are weaker then C-F bonds therefore can break in presence of UV radiation creating chlorine radicals which can attack ozone

Question 30

give the mechanism for the reaction of a haloalkane with aqueous potassium hydroxide

Question 31

what are the conditions for the reaction of aqueous potassium hydroxide and a haloalkane to form an alcohol?

Answer 31

• warm aqueous hydroxide
• under reflux

Question 32

give the mechanism for the reaction between potassium cyanide and a haloalkane

Question 33

what are the conditions for the reaction of potassium cyanide and a haloalkane

Answer 33

• warm ethanolic cyanide
  -reflux

Question 34

give the mechanism between ammonia and a haloalkane

Question 35

what are the conditions for ammonia reacting with a haloalkane to form an amine?

Answer 35

• excess ethanolic ammonia
• high pressure as ammonia will evaporate

Question 36

give two equations to show why both cyanide and ammonia have to be ethanolic when reacting with haloalkane

Question 37

give the elimination reaction between ethanolic potassium hydroxide and a haloalkane. what does it form?

Question 38

what are the conditions for the elimination reaction between hydroxide and a haloalkane?

Answer 38

• ethanolic hydroxide
• reflux