MediumChemistryHigh School (11–12)Organic Compounds with Functional Groups › Alcohols, Phenols and EthersNumerical

A student oxidises 4.50 g of propan-2-ol with acidified potassium dichromate…

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A student oxidises $4.50\ \text{g}$ of propan-2-ol with acidified potassium dichromate. One mole of $\text{K}_{2}\text{Cr}_{2}\text{O}_{7}$ oxidises three moles of the alcohol to the ketone. Use $60.096\ \text{g/mol}$ for propan-2-ol, $58.080\ \text{g/mol}$ for propanone and $294.181\ \text{g/mol}$ for $\text{K}_{2}\text{Cr}_{2}\text{O}_{7}$ . Find the amount of alcohol, the mass of propanone at an $80\ \%$ 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 $K_c = \dfrac{x^2}{(a - x)(b - x)}$ . Primary alcohols oxidise to aldehydes and acids, secondary alcohols to ketones, and tertiary alcohols are not oxidised.

The worked solution

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