3.3.5 Alcohols

Question 1

general formula of alcohols

Answer 1

CnH2n+1OH

Question 2

bond angle of H-C-H and C-C-O

Answer 2

109.5°

Question 3

bond angle of H-O-C

Answer 3

104.5°

Question 4

properties of alcohols

Answer 4

-low volatility
-high melting point
-smaller alcohols dissolve in water due to formation of H bonds.

Question 5

how are alcohols classified

Answer 5

primary, secondary and tertiary

Question 6

name the oxidising agent of alcohols

Answer 6

Acidified potassium dichromate (K2Cr2O7/H+)

Question 7

name the protuct formed from the oxidation and distillation of a primary alchol

Answer 7

aldehyde

Question 8

name the product formed from the oxidation under reflux of a primary alcohol

Answer 8

carboxylic acid

Question 9

name the product formed from the oxidation under reflux of a secondary alcohol

Answer 9

ketone

Question 10

what is the observation made in the oxidation of 1° and 2° alcohols

Answer 10

orange to green(Cr3+)

Question 11

In reflux condition, why should you never seal the end of the condenser

Answer 11

it would cause a build up of gas pressure causing apparatus to explode

Question 12

why are anti-bumping granule used in reflux and distillation

Answer 12

to prevent vigorous uneven boiling by forming small bubbles rather than large

Question 13

why are tertiary alcohols not oxidised by potassium dichromate

Answer 13

there is no hydrogen atom bonded to the carbon with the -OH
oxidation=loss of hydrogen

Question 14

name 2 reagents used to distinguish between aldehydes and ketones

Answer 14

tollen’s reagent
fehlings solution

Question 15

how is tollen’s reagent prepared

Answer 15

mixing aqueous ammonia and silver nitrate to form a complex ion

Question 16

describe the observation of aldehyde and ketone after the addition of tollen’s reagent and gentle heat

Answer 16

aldehyde=silver mirror forms
ketones=nvc

Question 17

describe the observation of aldehyde and ketone after the addition of fehling’s solution and gentle heat

Answer 17

aldehyde=blue to red ppt
ketones=nvc

Question 18

describe the test and observation for the presence of carboxylic acid

Answer 18

sodium carbonate
fizz to produce carbon dioxide

Question 19

define dehydration reaction

Answer 19

removal of a water molecule from a molecule

Question 20

name the product formed in the reaction of alcohols with dehydrating agents

Answer 20

alkene

Question 21

name the mechanism of the reaction of alcohols with dehydating agents

Answer 21

elimination

Question 22

name a dehydrating agent

Answer 22

concentrated surfuric or phosphoric acids

Question 23

what is the role of the dehydrating agent

Answer 23

catalyst

Question 24

name the condition required for the dehydration of alcohols

Answer 24

warm (under reflux)

Question 25

draw out the mechanism of acid catalysed elimation of propan-2-ol

Answer 25

-

Question 26

name the 2 methods for producing ethanol

Answer 26

-fermenation -direct hydration of ethene

Question 27

list 3 advantages of producing ethanol via fermentation

Answer 27

-sugar is a renewable resource -carbon neutral -production used low level technology/cheap equipment

Question 28

list 3 disadvantages of producing ethanol via fermentation

Answer 28

-batch process which is slow and gives high production costs -ethanol made is not pure and needs purifying by fractional distillation -depletes land used for growing food crops

Question 29

list 3 advantages of producing ethanol via dirent hydration of ethene

Answer 29

-faster reaction -purer product -continuous process=cheaper manpower

Question 30

list 3 disadvantages of producing ethanol via dirent hydration of ethene

Answer 30

-high technology equipment (expensive initial costs) -ethene is non-renewable resource -high energy costs to produce high pressure (70 atm)

Question 31

draw out the mechanism for the acid catalysed addition of ethene

Answer 31

-

Question 32

define biofuel e.g ethanol

Answer 32

fuel produced by plants

Question 33

define carbon neutral

Answer 33

an activity that has no net annual carbon (greenhouse gas) emissions to the atmosphere.

Question 34

why may ethanol produced via fermentation not be carbon neutral

Answer 34

it does not take into account energy needed to irrigate the plants, to distill the enthanol or porcess the fuel this energy would most likely come from burning fossil fuels