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| Question | Answer |
| What colour does ethanol burn with? | Pale blue flame |
| What happens to ethanol when it is burnt in oxygen? | The C-C and C-H bonds are broken as the ethanol is completely oxidised to make CO₂ and H₂O |
| Give the balanced symbol equation for the combustion of ethanol. | C₂H₅OH + 3O₂ --> 2CO₂ + 3H₂O |
| Apart from burning, what is another way of oxidising alcohols? | Use the oxidising agent acidified potassium dichromate (VI) (K₂Cr₂O₇/H₂SO₄) |
| What happens to the acidified potassium dichromate (VI) during an oxidation reaction? | The orange dichromate (VI) ion (Cr₂O₇²⁻) is reduced to the green chromium (III) ion (Cr³⁺) |
| Complete the sentences: A primary alcohol is first oxidised to an ______________. This _______________ can then be oxidised to a ______________ ______. | A primary alcohol is first oxidised to an ALDEHYDE. This ALDEHYDE can then be oxidised to a CARBOXYLIC ACID. |
| What does the notation [O] represent? | An oxidising agent |
| Describe the method of oxidising primary alcohols to aldehydes, including the reactants |
Gently heat the primary alcohol with potassium dichromate (VI) solution and sulfuric acid. The vaporised product will be distilled in a liebig condenser
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| During the oxidation of ethanol to an aldehyde, how do you know that the product is ethanal? | The product smells like apples |
| Give the equation for the oxidation of ethol into ethanal, showing the displayed formula of the reactants and products |
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| Describe the method of oxidising primary alcohols to carboxylic acids | The alcohol is mixed with excess oxidising agent and vigorously heated under reflux. |
| During the oxidation of ethanol to a carboxylic acid, how do you know that the product is ethanoic acid? | The product smells like vinegar |
| Why is it important to oxidise an alcohol under reflux (primary alcohol --> carboxylic acid) |
Heating under reflux means you can increase the temperature of an organic reaction to boiling without losing volatile solvents, reactants or products. Any vaporised compounds are cooled, condense and drip back into the reaction mixture
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| Give the equation for the oxidation of ethol into ethanoic acid, showing the displayed formula of the reactants and products |
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| What is the product of oxidising a secondary alcohol with acidified dichromate (VI)? | Ketone |
| TRUE OR FALSE: Ketones can be oxidised further by reflux | FALSE Ketones can't be oxidised easily, so even prolonged refluxing won't produce anything more |
| Give the equation for the oxidation of propan-2-ol into propanone, showing the displayed formula of the reactants and products |
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| What is the product of oxidising a secondary alcohol with acidified dichromate (VI)? | Nothing - tertiary alcohols don't react with acidified potassium dichromate (VI) at all. |
| What is the only way to oxidise tertiary alcohols? | By burning them |
| How can you distinguish tertiary alcohols from primary and secondary alcohols? | Heat a sample of an unknown alcohol in a test tube with a few drops of orange potassium dichromate (VI) and a few drops of concentrated sulfuric acid. If the alcohol is... Tertiary = solution stays orange Secondary/primary = orange --> green (as alcohol is oxidised and orange dichromate (VI) ions are reduced to green chromium (III) ions) |
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