Benedict's Test for Reducing Sugars
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Questions and Answers

What is the primary reason why some sugars like glucose are called reducing sugars?

  • They lack any functional groups.
  • They contain complex carbohydrates.
  • They have free ketone or aldehyde groups. (correct)
  • They are incapable of transferring hydrogens.

    • Which component in Benedict's reagent provides the necessary alkaline conditions?

  • Sodium bicarbonate
  • Sodium carbonate (correct)
  • Sodium hydroxide
  • Sodium chloride

    • What color change occurs in a positive Benedict's test?

  • Yellow to blue
  • Blue to orange red/ brick red (correct)
  • Green to blue
  • Blue to green

    • Which of the following sugars does not react with Benedict's reagent?

    <p>Sucrose</p> Signup and view all the answers

    What is the role of sodium citrate in Benedict's reagent?

    <p>To form complexes with copper(II) ions</p> Signup and view all the answers

    In the context of Benedict's test, which of the following is not a reducing sugar?

    <p>Starch</p> Signup and view all the answers

    Study Notes

    Benedict's Test

    • Identifies reducing sugars (monosaccharides) with free ketone or aldehyde functional groups.
    • Reducing sugars, like glucose, can transfer hydrogens (electrons) to other compounds, causing a reduction reaction.

    Characteristics of Reducing Sugars

    • All monosaccharides are reducing sugars due to their exposed carbonyl group.
    • Some disaccharides, like sucrose, are non-reducing sugars and won't react with Benedict's reagent.
    • Large polymers of glucose, such as starch, are not reducing sugars.

    Principle of Benedict's Test

    • Heating Benedict's solution with simple carbohydrates causes a color change to orange-red/brick-red.
    • Copper (II) ions in the solution are reduced to Copper (I) ions, leading to the color change.
    • Red copper(I) oxide formed is insoluble in water and precipitates out of solution, forming a precipitate.

    Benedict Reagent

    • Sodium carbonate provides alkaline conditions necessary for the redox reaction.
    • Sodium citrate complexes with copper (II) ions to prevent deterioration to copper(I) ions during storage.

    Objective and Specificity

    • The objective of Benedict's test is to distinguish between reducing and non-reducing sugars.
    • Benedict's test is specific for reducing sugars.

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    Description

    Identify reducing sugars with Benedicts reagent. Learn about monosaccharides, reduction reactions and color changes.

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