CL 14- alcohols

Question 1

explain the solubility of alcohols

Answer 1

• completely soluble in water
• as hydrogen bonds form between the polar -OH group of the alcohol and the water molecules

Question 2

volatility

definition

Answer 2

the tendency of a substance to vapourise

Question 3

explain the relatively low volatility of alcohols compared with alkanes

Answer 3

more energy is required to overcome the hydrogen bonds in the alcohol than the weaker London forces in alkanes

Question 4

explain how to classify alcohols into primary, secondary and tertiary

Answer 4

• classification depends on the number of carbon atoms directly attached to the C with -OH group
  primary–> 1 C
  secondary–> 2 C
  tertiary–> 3 C

Question 5

will propan-1-ol or propane burn better?

complete combustion

Answer 5

• propan-1-ol
• because it already has O
• less O₂ from the air needed

Question 6

test for alcohols

Answer 6

• add K₂Cr₂O₇ acidified with H₂SO₄
• if oxidation occurs (primary and secondary) solution turns green
• if no oxidation (tertiary) solution stays orange

Question 7

ionic half equation for acidified potassium dichromate

Answer 7

Cr₂O₇²⁻ –> Cr³⁺ + e⁻

Question 8

primary alcohols

oxidised to

Answer 8

• aldehydes under distillation
• carboxylic acids under reflux

Question 9

secondary alcohols

oxidised to

Answer 9

• ketones under reflux

Question 10

elimination reaction

Answer 10

removal of a small molecule, often water

Question 11

explain why the reaction of ethanol with HBr to form a haloalkane is a substitution reaction

Answer 11

the halogen replaced the -OH group in the alkane to form the haloalkane