# DBT JRF 2022 — Question 37

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

## Question

If you mixed 20 mL of 50 mM sodium acetate (NaOAc) with 30 mL of 25 mM glucose, what would be the concentration of each in the final solution?

## Options

- **A.** 50 mM NaOAc, 25 mM Glucose
- **B.** 20 mM NaOAc, 15 mM Glucose
- **C.** 30 mM NaOAc, 20 mM Glucose
- **D.** 40 mM NaOAc, 10 mM Glucose

## Answer

Option B

## Explanation

Mixing solutions — concentration after combining: Using conservation of moles: moles = concentration × volume, and final concentration = moles ÷ total volume. Final volume = 20 mL + 30 mL = 50 mL • NaOAc: $\frac{50\,\text{mM} \times 20\,\text{mL}}{50\,\text{mL}} = \frac{1000}{50} = 20\,\text{mM}$ • Glucose: $\frac{25\,\text{mM} \times 30\,\text{mL}}{50\,\text{mL}} = \frac{750}{50} = 15\,\text{mM}$ Note: NaOAc and glucose are in separate solutions being mixed; they do not chemically interact. The calculation is a simple dilution for each component independently. Answer: 20 mM NaOAc, 15 mM Glucose (Option 2).

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