Virtual Labs

1. Which of the following is a reducing sugar?

a: Glucose Explanation

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b: Sucrose Explanation

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c: Starch Explanation

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d: Cellulose Explanation

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2. Reducing sugars are characterized by the presence of which functional group?

a: Carboxyl (-COOH) Explanation

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b: Ketone (-C=O) or Aldehyde (-CHO) Explanation

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c: Hydroxyl (-OH) Explanation

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d: Amine (-NH₂) Explanation

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3. Which of the following is NOT a non-reducing sugar?

a: Sucrose Explanation

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b: Lactose Explanation

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c: Trehalose Explanation

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d: Raffinose Explanation

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4. In the DNS method, what is the role of 3,5-dinitrosalicylic acid?

a: It hydrolyzes non-reducing sugars. Explanation

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b: It forms a colored complex with reducing sugars. Explanation

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c: It stabilizes the reaction under acidic conditions. Explanation

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d: It precipitates the sugar from the solution. Explanation

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5. At what wavelength is the absorbance measured in the DNS method?

a: 340 nm Explanation

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b: 540 nm Explanation

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c: 620 nm Explanation

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d: 450 nm Explanation

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6. In Benedict’s test, the formation of a red precipitate indicates the presence of:

a: Starch Explanation

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b: Non-reducing sugars Explanation

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c: Reducing sugars Explanation

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d: Amino acids Explanation

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7. What is the chemical nature of the precipitate formed in Benedict’s test?

a: Copper(I) oxide (Cu₂O) Explanation

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b: Copper(II) sulfate (CuSO₄) Explanation

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c: Iron(III) hydroxide (Fe(OH)₃) Explanation

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d: Calcium carbonate (CaCO₃) Explanation

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8. The formation of a brick-red precipitate in Fehling’s test confirms the presence of:

a: Non-reducing sugars Explanation

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b: Lipids Explanation

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c: Reducing sugars Explanation

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d: Proteins Explanation

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9. Which treatment is necessary to detect non-reducing sugars in a sample?

a: Boiling with Benedict’s reagent Explanation

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b: Heating with dilute acid (e.g., HCl) followed by neutralization Explanation

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c: Mixing with DNS reagent directly Explanation

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d: No additional treatment is required Explanation

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10. Which method is most commonly used for quantitative estimation of reducing sugars?

a: Benedict’s test Explanation

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b: DNS method Explanation

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c: Fehling’s test Explanation

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d: Iodine test Explanation

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Quantitative estimation of sugars