Alkanes

Question 1

are alkanes saturated or unsaturated

Answer 1

saturated

Question 2

general formula of alkanes

Answer 2

CnH2n+2

Question 3

are alkanes soluble in water

Answer 3

no they are insoluble

Question 4

as the length of the carbon chain of an alkane increases, what happens to the boiling point

Answer 4

increases

Question 5

do straight chain alkanes or branched chain alkanes have a higher boiling point

Answer 5

straight chain

Question 6

what is the main use for alkanes

Answer 6

fuels

Question 7

what is crude oil

Answer 7

a fossil fuel that contains alkanes

Question 8

how is crude oil separated into shorter chain alkanes for use

Answer 8

fractional distillation

Question 9

do longer chain alkanes or shorter chain alkanes have a higher boiling point

Answer 9

longer chain alkanes

Question 10

why do longer chain alkanes have a higher boiling point

Answer 10

they have a higher surface area for the formation of Van der Waals forces so take more energy to break

Question 11

what is cracking

Answer 11

converting large hydrocarbons into smaller hydrocarbons by breaking C-C bonds

Question 12

what do longer chain alkanes get cracked to form

Answer 12

shorter chain alkanes and alkenes

Question 13

what are the economical reasons for cracking

Answer 13

shorter chain alkanes are in higher demand
products of cracking are more valuable than the starting materials

Question 14

what are the 2 types of cracking

Answer 14

thermal and catalytic

Question 15

temp of thermal cracking

Answer 15

400-900 degrees

Question 16

pressure of thermal cracking

Answer 16

70 atm

Question 17

what are the main products of thermal cracking

Answer 17

mainly alkenes

Question 18

temp of catalytic cracking

Answer 18

450 degrees

Question 19

pressure of catalytic cracking

Answer 19

slight pressure (over 1 atm)

Question 20

what type of cracking requires a zeolite catalyst

Answer 20

catalytic cracking

Question 21

what kind of cracking is homolytic fission

Answer 21

thermal

Question 22

what kind of cracking is heterolytic fission

Answer 22

catalytic cracking

Question 23

what type of cracking is a free radical mechanism

Answer 23

thermal cracking

Question 24

what kind of cracking is a carbocation mechanism

Answer 24

catalytic cracking

Question 25

what are the main products of catalytic cracking

Answer 25

motor fuels (branched alkanes) and aromatic hydrocarbons

Question 26

why is catalytic cracking more economic than thermal

Answer 26

requires less temp and pressure so less energy

Question 27

what is a fuel

Answer 27

releases heat energy when burnt

Question 28

what are the products of the complete combustion of alkanes

Answer 28

carbon dioxide and water

Question 29

what are the products of the incomplete combustion of alkanes

Answer 29

CO / C / H2O

Question 30

pollutants caused by combustion

Answer 30

nitrogen oxides CO O2 unburnt hydrocarbons soot

Question 31

what metals are in a catalytic convertor

Answer 31

platinum, palladium, rhodium

Question 32

what is the mechanism for halogenation

Answer 32

free radical substitution

Question 33

what are the 3 steps of halogenation

Answer 33

initiation propagation termination

Question 34

what happens in the initiation process of halogenation

Answer 34

UV light supplies energy to break apart the halogen. (eg Cl2 goes to 2Cl.) This is homolytic fission and each atom gets one electron. Forms free radicals which are represented by a dot

Question 35

are there free radicals in the products or reactants during propogation

Answer 35

there are free radicals in both the reactants and the products