Required practical 5 :Distillation of a product from a reaction.

Question 1

Apparatus for distillation

Answer 1

-Round-bottom flask
-condenser (horizontal) -water in at the bottom and out at the top
-Heat source (Bunsen)
-Thermometer
Collection vessel - in ice water bath
- anti-bumping granules

Question 2

What is the role of the anti bumping granules in this experiment?

Answer 2

Stops the mixture boiling too vigorously by preventing the formation of large bubbles.

Question 3

Write an balanced symbol equation for the reaction that has occurred between ethanol and the limiting acidified potassium dichromate - use [O] to represent your oxidising agent.

Answer 3

CH3CH2OH + [O] → CH3CHO + H2O

Question 4

If we had used excess potassium dichromate and reflux what organic product would we have obtained? Write an equation to represent this.

carboxylic acid

Answer 4

CH3CH2OH + 2[O] → CH3COOH + H2O

Question 5

What is the Tollens solution acting as?
What is the organic production in the Tollens test?

Answer 5

• Tollens = oxidising agent
• organic product = ethanoic acid

Question 6

Distinguishing between aldehyde and ketone ( tollens reagent )

Answer 6

(Making Tollen’s Reagent)
- mix aqueous ammonia to silver nitrate

Aldehyde: oxidised by Tollens’ reagent into a carboxylic acid. The silver(I) ions are reduced to silver atoms

Observation: with aldehydes, a silver mirror
forms coating the inside of the test tube.
Ketones result in no visible change

Question 7

Distinguishing between aldehyde and ketone (Fehling’s solution)

Answer 7

Reagent: Fehling’s solution containing blue Cu 2+ ions.

Conditions: heat gently

Reaction: aldehydes only are oxidised by
Fehling’s solution into a carboxylic acid. The
copper (II) ions are reduced to copper(I)
oxide .

Observation: Aldehydes :Blue Cu 2+ ions in solution change to a red precipitate of Cu2O.
Ketones do not react