Benedict\'s test is used for carbohydrates. It will show positive for monosaccha

Question

Benedict's test is used for carbohydrates. It will show positive for monosaccharides

But Sucrose is a disaccharide and starch is a polysaccharide.

On addition of acid (here HCl) both sucrose and starch gets hydrolysed. On hydrolysing Sucrose it forms Glucose and Fructose and starch forms glucose and some other monosaccharides. As these formed glucose, fructose are monosaccharides they show positive for Benedict's test. So Benedict's test is positive for sucrose with HCl and starch with HCl. whereas sucrose and starch are not hydrolysed by adding H2O so they show negative with Benedict's test

Iodine test is used for starch. It shows positive for starch and negative for rest of carbohydrates.

So it shows negative for both sucrose with H2O and HCl,and also for starch+HCl as it hydrolyses into glucose. But It shows positive for starch+H2O because it is not hydrolysed.

Benedict's test- Green to Dark Red - positive otherwise negative

Iodine test - Purple Black colour - positive otherwise negative

Result Sucrose+H2O Sucrose+HCl Starch+H2O Starch+HCl 1.Iodine negative negative positive negative 2.Benedict's test negative positive negative positive 3.Hydrolysis yes/no no yes no yes

Explanation / Answer

E. Hydrolysis of disaccharides and polysaccharides Result Sucrose + H20 SucroseHCI Starch + H20 Sucrose + HC 1. Iodine 2. Benedict's test 3. Hydrolysis Yes/No

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