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Testing carbohydrates. Quantitative Benedict’s Results and Acid Hydrolysis of Sucrose.

Testing carbohydrates. Quantitative Benedict’s Results and Acid Hydrolysis of Sucrose. Objectives. Be able to describe and explain how to use a colorimeter. Plot a calibration curve and use it to find the concentration of an unknown solution.

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Testing carbohydrates. Quantitative Benedict’s Results and Acid Hydrolysis of Sucrose.

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  1. Testing carbohydrates. Quantitative Benedict’s Results and Acid Hydrolysis of Sucrose.

  2. Objectives • Be able to describe and explain how to use a colorimeter. • Plot a calibration curve and use it to find the concentration of an unknown solution. • Explain how to test for a non-reducing sugar using acid hydrolysis.

  3. How would you determine the concentration of a solution of glucose using the Benedict’s test. -Take a set of standard solutions. -Add Benedict’s reagent. Heat in a water bath for 5 minutes. -Filter off the precipitate -Measure the absorbance of the liquid using a colorimeter. -Plot a calibration curve -Compare the absorbance of the unknown solution to the calibration curve.

  4. Acid Hydrolysis of Sucrose -Sucrose is non-reducing sugar. -However it can be hydrolysed with acid. -Why would hydrolysis of sucrose cause reducing sugars to be present?

  5. Acid Hydrolysis of Sucrose -Add a small amount of sucrose to a boiling tube. -Add a few drops of dilute sulphuric acid. -Neutralise with sodium hydroxide . -Carry out the Benedicts test Test for a non-reducing sugar = Benedicts turns brick red after acid hydrolysis.

  6. Using a colorimeter -Filter off the liquid from the precipitate and place in a cuvette. -Measure the absorbance using 630nm wavelength. -Plot a calibration curve. Absorbance Concentration

  7. Colorimeter -Filter off the liquid from the precipitate and place in a cuvette. -Measure the absorbance using 630nm wavelength. -Plot a calibration curve. Acid hydrolysis -Add a small amount of sucrose to a boiling tube. -Add a few drops of dilute sulphuric acid. -Neutralise with sodium hydroxide . -Carry out the Benedict’s test Absorbance Concentration

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