CP5 - Oxidation Of Ethanol Flashcards
What is oxidation?
• Oxidation is loss of electrons.
• If an element is oxidised, it’s oxidation number increases.
What is distillation?
• Distillation is a technique where the heating of a liquid to create a vapour is cooled by a condenser, causing the gas to condense into a liquid and drip into a separate flask.
• The different substances will be separated by boiling point/volatility.
What equipment is used for distillation?
Quickfit apparatus:
• Pear-shaped or round-bottomed flask with a liebig condenser, still head, stopper, receiver adaptor, fitted with a thermometer and collection vessel.
What does a diagram of Quickfit apparatus set up for distillation look like?
Draw it and check in notes - paper 3 chem diagrams
What happens when you oxidise ethanol by distillation?
• Ethanol is distilled with acidified potassium dichromate (VI) and is oxidised into an aldehyde, ethanal.
• This is shown by a colour change from orange to green
What is the equation for the oxidation of ethanol to ethanal?
CH3CH2OH + 2[O]——> CH3CHO +H2O
[O] is acidified potassium dichromate (K2Cr2O7)
Acidified using dilute sulfuric acid
How do you use laboratory equipment to heat under reflux?
Quickfit apparatus is used to heat a substance under reflux.
- The substance is boiled in a pear-shaped or round-bottomed flask.
- As it evaporates, it is cooled by the water in the liebig condenser and so condenses back into a liquid and drips back down into the flask to be heated again.
Why is heating under reflux used?
• Allows heating for a long period of time
• Prevents the flask from boiling dry
• Prevents volatile reactants/products escaping
• Ensures even heating
What does a diagram of Quickfit apparatus set up for heating under reflux look like?
Draw and check in notes
Why are anti-bumping granules used when heating under reflux/in distillation?
To allow smooth boiling. They prevent the appearance of bubbles caused by vapour in the hot liquid which would cause splashing up the sides of the flask.
What happens when you oxidise ethanol under reflux?
• Ethanol is refluxed with acidified potassium dichromate (VI) and is oxidised into a carboxylic acid, ethanoic acid.
• This is shown by a colour change from orange to green.
What is the equation for the oxidation of ethanol to ethanoic acid?
What is the equation for the oxidation of ethanol to ethanoic acid?
CH3CH2OH + 2[O] —> CH3COOH +H2O
[O] - H2SO4/K2CrO7
Reflux
What are some potential hazards and risks in the laboratory?
-Bunsen - burns - keep away from flammable chemicals and away from edge of desk
-Ethanol - Flammable - away from open flame on bunsen, eye protection
-potassium dichromate - irritant - goggles, gloves and don’t ingest or inhale
-glassware eg beakers and test tubes - break and cut you - away from edge of desk
In the equipment set up why is water in from the bottom?
So the water moves up against gravity and covers the condenser therefore ensuring effective cooling of evaporated reactants in reflux
