organic chem

Question 1

what are hydrocarbons

Answer 1

A substance with molecules that contain only carbon and hydrogen atoms.​

Question 2

how many bonds can a carbon atom form

Answer 2

4

Question 3

why are alkanes saturated

Answer 3

they contain the maximum number of hydrogen atoms for each carbon atom.

Question 4

how many bonds are between carbon atoms in alkenes

Answer 4

double bond (C=C)

Question 5

why does methene not exist

Answer 5

bc meth has only 1 carbon bond, methane exists bc alkanes have only 1 carbon bond

Question 6

name the first 4 alkanes

Answer 6

methane,ethane,propane,butane

Question 7

why are alkenes unsaturated

Answer 7

they contain less than the maximum number of hydrogens per carbon.

Question 8

whats the general formula for alkenes

Answer 8

CnH2n

Question 9

define voltality

Answer 9

the tendency of a substance to turn from liquid to gas (evaporate)

Question 10

whats the general formula for alkanes

Answer 10

CnH2n+2

Question 11

viscosity

Answer 11

a liquids resistance to flow

Question 12

whatre the properties of short chain hydrocarbons

Answer 12

-lower boiling point and viscosity
-higher volatility and flammability

Question 13

whatre the properties of long chain hydrocarbons

Answer 13

• high boiling point and viscosity
  -lower volatility and flammability

Question 14

whatre the steps in fractional distillation

Answer 14

1- crude oil is heated then vapourised -> goes into bottom of fractional tower
2-short chain hydrocarbons vapourise then cool as thet rise due to a lower boiling point
3- long chain hydrocarbons vapourise and condense at the bottom as they have a higher boiling point
the bottom of tower is hotter than top
4- fractions condense and cool

Question 15

why do we use fractional distilation

Answer 15

to seperate different fractions of hydrocarbons in crude oil depending on their boiling point, short chains are more useful

Question 16

which comes first, cracking or fractional distilation

Answer 16

fractional distilation, cracking breaks down larger fractions from the top of fractionating tower into more usefull shorter hydrocarbons

Question 17

what are the 2 types of cracking

Answer 17

• steam cracking and catalyctic cracking

Question 18

what gases are released when fuels are burnt

Answer 18

• carbon dioxide
• water vapours
  -carbon monoxide (odourless and colourless gas)
• sulfer dioxide
  -nitrogen oxides (formed at high temp)
• solid particles (soot(carbon) and unburnt fuels)

Question 19

whatre the 3 effects of burning fuels

Answer 19

• acid rain (nitrogen oxide and sulfer dioxide)
• climate change (carbon dioxide)
  -global dimming (solid particles)

Question 20

what happens during the combusion of hydrocarbons

Answer 20

• carbon and hydrogen are oxidised(gains oxygen )
  -fuels release energy

Question 21

hydrocarbons + oxygen ->

Answer 21

carbon dioxide+ water

Question 22

hydrocarbon + low oxygen supply

Answer 22

carbon monoxide

Question 23

carbon with no oxygen

Answer 23

carbon particles (soot)

Question 24

whatre the 2 ways ethanol (a biofuel) can be made

Answer 24

1- reacting ethene with steam (uses phosphoric acid catalyst but ethene is from crude oil which is nonrenewable)
2- fermenting glucose at 20-35 degrees (using enzymes in yeast which is a natural catalyst and renewable resource)

Question 25

whatre the advantages of using biofuels

Answer 25

- biodiesel spillage is less harmful than spilling crude oil since it burns cleanly and reduces sulfer dioxide emissions - biofuels will become cheaper - carbon nutral since co2 in=co2 out

Question 26

what are the disadvantages of biofuels

Answer 26

-famland used to grow biofuels instead of food will cause famine(starvation) in poorer countries -habitats destroyed from deforestation which decreases biodiversity

Question 27

describe the cracking process

Answer 27

- heat then vapourise the hydrocarbon - vapours are either passed over a hot catalyst or steam with very high pressure

Question 28

how can alkenes be told apart from alkanes

Answer 28

bromine water turns colourless

Question 29

which hydrocarbon can make polymers,give an example

Answer 29

- alkenes - ex poly(ethene)

Question 30

what happens in polymerisation reactions

Answer 30

many monomers (smaller molecules) join together to form polymers

Question 31

what do properties of polymers depend on

Answer 31

conditions theyre made under and what theyre made of

Question 32

what are thermosoftening polymers

Answer 32

polymers that consist of tangled polymer chains with no crosslinks between them

Question 33

why do thermosoftening polymers melt easily

Answer 33

they have weak intermolecular forces which allows them to be easily remoulded

Question 34

whatre cross links

Answer 34

strong covalent bonds

Question 35

what are thermosetting polymers

Answer 35

polymers that consist of polymer chains with cross linkks between them

Question 36

why do thermosetting polymers not melt easily

Answer 36

they have strong covalent cross link bonds that require loads of energyt o seperate/ break apart

Question 37

why is it an issue if polymers arent biodegradable (break down by microbes)

Answer 37

theyre desposed but dont break up for years which causes them to be carried by oceans to form garbage patches which marine animals consume

Question 38

why are plastic bangs made of polymers and cornstarch

Answer 38

so they become biodegradabke and break down easily so less damage is caused to the environment

Question 39

what functional group do alcohold contain

Answer 39

-OH

Question 40

whatre the uses and properties of alcohols

Answer 40

- flammable and can undergo complete combustion -soluble (dissove in water to form neutral solutions) -burn in air -used as fuels and solvents ethanol used in alcoholic drinks

Question 41

whatre the 2 ways ethanol can be oxidised to form ethanoic acid

Answer 41

-chemical oxidising agents -microbial actions

Question 42

whats the main acid in vinegar

Answer 42

ethanoic acid

Question 43

whats the functional group for carboxylic acids

Answer 43

-COOH

Question 43

whatre the properties of carboxylic acids

Answer 43

they react with cabonates to form carbon dioxide dissolve in water to form acidic solutions react with alcohols in the presence of acid catalyst to form esters dont ionise completely so theyre weak acids

Question 43

whats the functional group for esters

Answer 43

coo

Question 44

how is ethanyl ethanoate formed

Answer 44

by reacting ethanol and ethanoic acid with the presence of an acid catalyst

Question 45

why are esters used as flavourings and perfumes

Answer 45

cause they have distinctive smells and are voltalite