96. The volume (in mL) required to prepare 350 mL of 1X buffer solution from a fifty times (50X) concentrated buffer stock solution is ________.
Volume Required to Prepare 350 mL of 1X Buffer from a 50X Stock Solution
Correct Answer
✅ Correct Answer: 7 mL
Understanding the Dilution Formula
Whenever a concentrated stock solution is diluted to prepare a working solution, the total amount of solute remains unchanged. This relationship is expressed by the standard dilution equation:
C1V1 = C2V2
where:
- C1 = Concentration of the stock solution
- V1 = Volume of stock solution required
- C2 = Final concentration
- V2 = Final volume of the solution
Given Data
Stock concentration (C1) = 50X
Final concentration (C2) = 1X
Final volume (V2) = 350 mL
Volume required (V1) = ?
Step-by-Step Calculation
Applying the dilution equation:
C1V1 = C2V2
Substitute the given values:
50 × V1 = 1 × 350
V1 = 350 / 50
V1 = 7 mL
Therefore, 7 mL of the 50X stock solution is required.
Preparation of the Buffer
To prepare the desired buffer:
- Measure 7 mL of the 50X stock buffer.
- Add distilled water until the total volume becomes 350 mL.
- The resulting solution will have a final concentration of 1X.
Why the Dilution Formula Works
Dilution changes only the concentration of the solution by increasing the amount of solvent. The number of moles of buffer components remains constant before and after dilution. Since the amount of solute does not change, the product of concentration and volume remains constant, giving rise to the equation C1V1 = C2V2.
Concept Behind the Question
This question evaluates one of the most essential laboratory skills in molecular biology and biochemistry. Preparing working solutions from concentrated stock solutions is a routine laboratory procedure. Students should always remember that the dilution equation can be applied whenever only the concentration changes while the amount of solute remains constant.
Final Answer
Using the dilution equation, the volume of 50X stock buffer required to prepare 350 mL of a 1X working solution is:
V1 = 7 mL
✅ Correct Answer: 7 mL
