A syrup contains 100 g of sucrose (342.30 g/mol) and is hydrolysed completely…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A syrup contains of sucrose () and is hydrolysed completely. The products are dissolved to make . Glucose has a molar mass of and a specific rotation of degrees. Fructose has the same molar mass and a specific rotation of degrees. Find the mass of glucose and of fructose that forms, and the observed rotation in a tube long.
Need a reminder? The key ideaShow
A glycosidic link releases one molecule of water, so units in a chain have links. Hydrolysis adds the water back. Sucrose gives equal moles of glucose and fructose. The observed rotation of a mixture is the sum of the contributions of each sugar: .
The worked solution
Have you tried it?
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.
Plan. Equal moles of the two hexoses form. Their rotations add.
Step 1. Moles of sucrose. . The same amount of each hexose forms.
Step 2. Masses. of glucose and of fructose.
Step 3. Concentration. of each.
Step 4. Rotation. degrees.
Answer: of each sugar, and an observed rotation of degrees.
Check. The two masses add to , which is more than of sucrose, because water has been added in the hydrolysis.
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