A student oxidises 4.50 g of propan-2-ol with acidified potassium dichromate…
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A student oxidises of propan-2-ol with acidified potassium dichromate. One mole of oxidises three moles of the alcohol to the ketone. Use for propan-2-ol, for propanone and for . Find the amount of alcohol, the mass of propanone at an yield and the least mass of dichromate needed.
Need a reminder? The key ideaShow
Lucas test: tertiary at once, secondary in about five minutes, primary clear at room temperature. Dehydration follows Saytzeff's rule. Esterification is an equilibrium with . Primary alcohols oxidise to aldehydes and acids, secondary alcohols to ketones, and tertiary alcohols are not oxidised.
The worked solution
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Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Given. of propan-2-ol, yield.
Step 1. Alcohol. .
Step 2. Propanone. Theoretical: . At : .
Step 3. Dichromate. . Mass: .
Check. The dichromate turns from orange to green as it is used. A little more than the least mass is used in practice.
Answer: , and .
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