Test for sucrose by acid hydrolysis followed by Benedict's reagent, and for protein using the Biuret test (sodium hydroxide and copper sulfate).
To test for sucrose and protein, first hydrolyze sucrose with acid and heat, then test with Benedict's reagent for reducing sugars (from hydrolysis). Then, test for protein using sodium hydroxide and copper sulfate, looking for a purple ring.
| Front | A solution which tested negative for reducing sugars was thought to contain sucrose and protein. Describe how you would find out whether this was so (6 marks) |
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| Back | mix equal volumes of solution and dilute hydrochloric acid; boil in a water bath (for 2 minutes) to hydrolyse sucrose (to glucose and fructose); mix with equal volumes of Benedict’s reagent; boil in water bath (for 2 minutes); if brick red precipitate appears then sucrose is present; mix equal volumes of solution and (dilute/5 %) sodium hydroxide run dilute/1% copper sulphate solution into the solution a purple ring at the interface indicates protein is present; |
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