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A sugar of molar mass 150 g/mol contains 40.0% carbon, 6.7% hydrogen and 53.3% oxygen by mass…

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A sugar of molar mass $150\ \text{g/mol}$ contains $40.0\%$ carbon, $6.7\%$ hydrogen and $53.3\%$ oxygen by mass. Take C as $12.011\ \text{g/mol}$ , H as $1.008\ \text{g/mol}$ and O as $15.999\ \text{g/mol}$ . Find the empirical formula, then the molecular formula. If the sugar is an aldopentose with an unbranched chain, how many stereoisomers does it have?

Need a reminder? The key ideaShow

A carbohydrate is a polyhydroxy aldehyde or ketone. An aldose has $n - 2$ stereocentres and a ketose has $n - 3$ , where $n$ is the number of carbons in the chain. The number of stereoisomers is $2^{\text{centres}}$ , and half of them belong to the D series. An empirical formula comes from the moles of each element in 100 g.

The worked solution

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