C6.2- Organic chemistry (homologous series)

Question 1

define an alkane

Answer 1

a saturated hydrocarbon with the formula Cn H2n+2, with the functional group CH^2

Question 2

acronym to remember first 5 members of alkane/alkene/alcohol/carboxylic acid series

Answer 2

M y
E lephant
P umps 
B alloons
P ainlessly 

Meth- 
eth- 
prop-
but-
pent-

Question 3

what is the molecular formula for an alkane?

Answer 3

C H

n 2n+2

Question 4

draw out the displayed formula for propane

Answer 4

H H H
     |   |   |
H-C-C-C-H
     |   |   | 
    H H H

Question 5

why are alkanes described as saturated hydrocarbons

Answer 5

• They have the maximum amount of hydrogen atoms

since they are joined by single covalent bonds

Question 6

write out the word equation for complete combustion of alkanes

Answer 6

alkane + oxygen -> water + carbon dioxide

Question 7

how do alkanes combust in a poor supply in oxygen? (write out the word equation)

Answer 7

alkane + oxygen -> carbon monoxide + carbon + water

Question 8

define an alkene

Answer 8

an unsaturated hydrocarbon made of ONLY hydrogen and carbon atoms, which contain one double carbon carbon covalent bond

Question 9

what is the molecular formula for alkenes?

Answer 9

C H

n 2n

Question 10

draw out the displayed formula for butene

Answer 10

H H H H  
     |   |   |   |
H-C-C=C-C-H
     |           |
    H         H

C4H8

Question 11

what is different about the first 4 alkene molecules compared to alkanes?

Answer 11

• there is no ‘methene’
• as 2 carbon atoms must be present for a double carbon molecule to be formed
• to produce an alkene

Question 12

how do alkenes react with plentiful oxygen?

Answer 12

alkene + oxygen -> carbon dioxide + water

SAME AS ALKANE

Question 13

how do alkenes combust with a limited supply of oxygen?

Answer 13

alkene + oxygen -> carbon monoxide + carbon + water

SAME AS ALKANE

Question 14

define a functional group

Answer 14

atom/bonds in a molecule that determines the chemical reactions of an organic compound

Question 15

what allows alkenes to undergo a wider range of reactions? (compared to alkanes)

Answer 15

a double carbon bond functional group

Question 16

what are addition reactions, and give two examples of them

Answer 16

• when an atom/group of atoms combine with a molecule to form a larger molecule (with NO OTHER PRODUCT)
• reaction with alkenes + bromine water
• reaction with alkenes + hydrogen

Question 17

what can the addition reaction between bromine water and alkenes be used to detect?

Answer 17

• test for unsaturation (ie. whether hydrocarbon is an alkene or not)

Question 18

describe how the addition reaction with bromine-water works (not in terms of bonds)

Answer 18

• bromine turns colourless with alkenes
• stays orange-brown with alkanes
• bromine reacts with alkenes, no reaction with alkanes

Question 19

describe what happens when hydrogen reacts with an alkene, and what the name for that type of reaction is

Answer 19

• called an addition reaction

- an alkane is formed

Question 20

write down the word equation for an addition reaction with hydrogen and alkene

Answer 20

alkene + hydrogen -> alkane

Question 21

how do you identify if something is an alcohol (suffix)

Answer 21

ends with ‘ol’

ie. butanol

Question 22

what is the functional groups of alcohols?

- and what is it called

Answer 22

‘OH’

- called the ‘hydroxyl’ group

Question 23

what is the molecular formula for alcohols?

Answer 23

C H OH

n 2n + 1

Question 24

draw out ethanol

and state one thing that is special about how it is drawn out

Answer 24

C H OH
2 5

     H    H 
      |      |
H--C----C---O----H
      |      |
     H    H

• the OH are separate at the side

Question 25

write out the word equation for the complete combustion of an alcohol

Answer 25

alcohol + oxygen -> water vapour + carbon dioxide

Question 26

write out the word equation for the incomplete combustion of an alcohol

Answer 26

alcohol + oxygen -> water vapour + carbon monoxide + carbon (ie. soot)

Question 27

how do you identify if something is part of the carboxylic acid homologous series? (in its name)

Answer 27

ends in 'anoic' acid

Question 28

what is the functional group of a carboxylic acid? | - and whats special about tit

Answer 28

-COOH C=O double bond at the top

Question 29

what is the molecular formula for carboxylic acids?

Answer 29

C H COOH | n 2n + 1

Question 30

why can carboxylic acids take part in different reactions to alkenes and alkanes?

Answer 30

as they have a COOH functional group

Question 31

draw out the structural formula for methanoic acid

Answer 31

HCOOH .......O .......|| H - C - O - H - remember it only has 1 carbon atom, and all carboxylic acids must have a -COOH functional group (so Cn = C0)

Question 32

draw out ethanoic acid

Answer 32

``` .......H....O ........|.....|| H - C - C - O - H ........| .......H ``` CH COOH 3

Question 33

draw out butanoic acid

Answer 33

``` H H H O | | | || H - C - C - C - C - O - H | | | H H H ``` C H COOH 3 7

Question 34

name the first 4 carboxylic acids

Answer 34

methanoic acid, ethanoic acid, propanoic acid, butanoic acid

Question 35

how are carboxylic acids made?

Answer 35

when alcohols are oxidised using potassium manganate (VII)

Question 36

describe an experiment to produce ethanoic acid from ethanol

Answer 36

1) acidify potassium manganate VII with dilute sulfuric acid 2) and add acidified potassium manganate VII oxidising agent to the ethanol 3) colour changes from purple to very pale pink - therefore an acidified solution is made

Question 37

safety when making a carboxylic acid from an alcohol?

Answer 37

- wear eye protection - stir reaction carefully (can be violent) - wear lab coat - potassium manganate can stain clothing + hands (i just thought of this so i’m not 100% sure)

Question 38

what can a carboxylic acid also be described as?

Answer 38

a weak acid (therefore reacts with metals, bases in the same way)

Question 39

what do salts produced with a carboxylic acid have the ending of? ie. ethanoic acid + sodium carbonate (write out all products of the reaction)

Answer 39

'oate' makes: sodium ethanoate + water + carbon dioxide