# DBT JRF 2022 — Question 6

Exam: DBT JRF 2022 · Section: A · Topic: Biochemistry › Solution Chemistry & Dilutions · Difficulty: Medium

## Question

You are given a 5 mM solution of sucrose. If you hydrolyse it by adding equal volume of 10 mM HCl, what would be the final concentration of glucose and fructose in the hydrolysate?

## Options

- **A.** 5 mM glucose and 5 mM fructose
- **B.** 2.5 mM glucose and 2.5 mM fructose
- **C.** 1.25 mM glucose and 1.25 mM fructose
- **D.** 1.25 mM glucose and 2.5 mM fructose

## Answer

Option B

## Explanation

Sucrose hydrolysis and dilution: Step 1 — Dilution: 5 mM sucrose + equal volume of 10 mM HCl → total volume doubled → sucrose concentration halved: $[\text{Sucrose}]_{\text{final}} = \frac{5\,\text{mM}}{2} = 2.5\,\text{mM}$ Step 2 — Hydrolysis: Sucrose → Glucose + Fructose (one-to-one stoichiometry) $\text{C}_{12}\text{H}_{22}\text{O}_{11} + \text{H}_2\text{O} \rightarrow \text{C}_6\text{H}_{12}\text{O}_6 + \text{C}_6\text{H}_{12}\text{O}_6$ 2.5 mM sucrose → 2.5 mM glucose + 2.5 mM fructose. Note: HCl acts as a catalyst for hydrolysis; it does not affect the stoichiometry. Answer: 2.5 mM glucose and 2.5 mM fructose (Option 2).

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