ORGANIC ANALYSIS/ALCOHOLS

Question 1

TEST for
Primary alcohol
Secondary alcohol
Aldehyde

Answer 1

Acidified pottasium dicromate
Orange to green

Question 2

TESTS for aldehyde

Answer 2

Tollens reagent
Silver mirror formed

Fehiling reagent
Brick red precipitate

Question 3

Test for alkene

Answer 3

Bromine water
Colourless solution

Question 4

Test for carboxylic acid

Answer 4

Na2CO3
EFFESRRVENCE

Question 5

Vibration and frequency of bonds

Answer 5

Strong bonds vibrate with very high frequency
Weak bonds vibrate with very low frequency

Question 6

Identification if a molecule by comparison of spectra

Answer 6

Use fingerprinting reagent and compare with known spectrum from database

Question 7

Whats the standard recfrence in mass soectrum

Answer 7

12C is standard refrence

Question 8

Why can’t we differentiate some molecules(2 mark points)

Answer 8

Molecules with same Mr to 1dp so can’t be differentiated
Some molecules have same Molecular formula

Question 9

Classification of alcohol

Answer 9

Primary
Secondary
Tertiary

Question 10

2 step process convert alcohol to carboxylic acid (pathway)

Answer 10

Step 1
Oxidation to aldehyde from alcohol
Step 2
Oxodation to carboxylic adid from aldehyde

Question 11

Why reflux id used to oxidise an alcohol into a carboxylic acid?

Answer 11

Reflux doesnt allow any reactant vapour to escape

Question 12

What happens during reflux? (3marks)

Answer 12

Reaction mixture is heated to boiling point
Vapour is formed ehich escapes from the liquid , this is condensed back into liquid and returned to the liquid mixture
Any compound that initially evaporates can be oxidised

Question 13

What are anti-bamping granelles added?

Answer 13

Prevent large bubbles forming

Question 14

Explain the process of distillation

Answer 14

Turn the water suupky on to the condenser
Heat the flask
(Aldehyde) will vaporise
Use thermometer to maintain the temperature at the Boiliing point of (ethanal)
The (ethanal) vapours condense back into a liquid in the condenser
(Ethanal) is coklected in a cooled container to avoid is vaporsing

Question 15

Explain the term biofuel (1mark)

Answer 15

Fuel produced from renewable plant material (biomass)

Question 16

Production if alcohol from crude oil

Answer 16

Reaction hydration
Catalyst concentrated H3PO4
Conditions steam, 450C , 100 pressure
Reagent H+ & H2O

Question 17

Production of ethanol via fermentation (condition + equation)

Answer 17

Yeast , no oxygen , 35C temp
C6H12O6 ——> CO2 + 2CH3CH2OH

Question 18

Advantages vs disadvantages of biofuel

Answer 18

Advantages
Comes from renewable raw material
Considered to be carbon neutra
Conserves crude oil supplies

Disadvantages
Biofuels cant be made on a scale to meet global demand for fuels
Supply of biofuels dependent on crop harvest so less relaible
Food prices rise as crops used for biofuels therefore increase market price

Question 19

Advantages and disadvantages of hydration of ethene

Answer 19

Advantages
Large scale production method
High purity product made
High rate of reaction
Continous production metod

Disadvantages
High temp & pressure so increases costs
Crude oil is non-renewable
Expensive & high equipment needed

Question 20

Advantages & disadvantages of fermentation

Answer 20

Advantages
Uses renewable resourses
Low cost
Low tech method
Readily available and renewable raw materials from plants

Disadvantages
Slow rate of reaction
Impure ethanol made needs distilling
Causes food prices to rise if crops are used to pridicr alcohol instead of food

Question 21

4 equation that show oxidation of alcohol

Answer 21

1.
CH3CH2OH +[O] ——> CH3CHO + H2O
2.
CH3CHO + [O] ———> CH3COOH
3.
CH3CH2OH + 2[O] ———-> CH3COOH + H2O
4.
CH3CH(OH)CH3 + [O] ———-> CH3COCH3 + H2O