Alcohols

Question 1

What is the alcohol group

Answer 1

OH-

Question 2

Boiling points of alcohols + why

Answer 2

Relatively high boiling points due to their ability to form hydrogen bonds between alcohol molecules

Question 3

What shape are alcohols (always) + bond angle

Answer 3

Tetrahedral
109°

Question 4

Different tropes of alcohols (3)

Answer 4

Primary: 1 carbon attached to OH

Secondary: 2 carbons attached to OH

Tertiary: 3 carbons attached to OH

Question 5

Oxidising agent of alcohols

Answer 5

K2Cr2O7
Potassium dichromate

Question 6

Why are anti-bumping granules added to the flask in both distillation and reflux

Answer 6

To prevent uneven biking by making small bubbles instead of large bubbles

Question 7

Distinguished between aldehydes and ketones

Answer 7

Aldehydes can be further oxidised to carboxylic acid
Ketones can not be further oxidised

Question 8

Two tests that are used to distinguish between aldehydes and ketones

Answer 8

Tollens reagent
Fehlings solution

Question 9

Tollens reagent

Answer 9

Reagent: Formed by mixing aqueous ammonia and silver nitrate.

Conditions: heat gently

Reaction: ALDEHYDES ONLY are oxidised by Tollens reagent. The silver (I) ions are reduced to silver atoms

Observation: with ALDEHYDES, a silver mirror forms coating the inside of the test tube
KETONES- no visible change

CH3CHO + 2Ag+ + H2O —> CH3COOH + 2Ag + 2H+

Question 11

Fehlings solution

Answer 11

Reagent: Fehlings solution contains BLUE Cu2+ ions.

Conditions: heat gently

Reaction: ALDEHYDES ONLY are oxidised by Fehlings solution into carboxylic acid. Copper (II) irons are reduced to copper (I) oxide.

Observation: ALDEHYDES: blue Cu2+ ions in solution changed to red precipitate of Cu20
KETONES do not react

CH3CHO + 2Cu2+ + 2H2O —> CH3COOH + Cu2O + 4H+

Question 12

How to test the presence of carboxylic acid

Answer 12

Adding sodium carbonate.

It will fizz and produce carbon dioxide

Question 13

Forming ethanol : fermentation

Answer 13

glucose —> ethanol plus carbon dioxide.

Conditions:
• yeast
• no air.
• temperatures 30 to 40°C

Question 14

Advantages of fermentation

Answer 14

• sugar is a renewable resource.
• production Users, low level technology/cheap equipment

Question 15

Disadvantages of fermentation

Answer 15

• batch process which is slow and gives high production cost
• ethanol made is not pure and needs purifying by fractional distillation.
• Depletes land use for growing food crops

Question 16

Forming ethanol: from ethane

Answer 16

Reagent: Ethan – from cracking of fractions from distilled crude oil.

Type of reaction: hydration/addition

Question 17

Advantages of forming ethanol from ethane

Answer 17

• faster reaction.
• pure product.
• continuous process (which means cheaper manpower)

Question 18

Disadvantages of forming ethanol from ethane

Answer 18

• high technology equipment needed (expensive initial cost)
• Ethene is non-renewable resource
• high energy cost for pumping to produce high pressures

Question 19

Hydration definition

Answer 19

Addition of water to molecule

Question 20

Essential conditions for forming ethanol from ethane

Answer 20

• high temperature 300°
• high-pressure 70 ATM
• Strong acidic catalyst of concentrated H3PO4