Q.47 The volume (in mL) required to prepare 350 mL of 1X buffer solution from a fifty times
(50X) concentrated buffer stock solution is ________.
The volume required from the 50X concentrated buffer stock to prepare 350 mL of 1X buffer solution is 7 mL. This calculation relies on the standard dilution formula \(C_1V_1 = C_2V_2\), where no options are provided in the question, confirming a numerical fill-in answer typical for CSIR NET Life Sciences exams.
Dilution Formula Explained
The equation \(C_1V_1 = C_2V_2\) balances the amount of solute before and after dilution. Here, \(C_1 = 50X\) (stock concentration), \(V_1\) is the unknown stock volume in mL, \(C_2 = 1X\) (final concentration), and \(V_2 = 350\) mL (final volume). Rearranging gives \(V_1 = \frac{C_2 V_2}{C_1} = \frac{1 \times 350}{50} = 7\) mL, verified through precise computation.
Step-by-Step Calculation
Start with known values: stock is 50 times concentrated, so 1 part stock dilutes into 50 parts total volume[web:6]. Divide final volume by concentration factor: \(350 \div 50 = 7\) mL stock, then add water to reach 350 mL total (343 mL water). This ensures the final 1X buffer maintains exact solute concentration for molecular biology applications like electrophoresis.
Common Mistakes to Avoid
- Pipetting errors occur with tiny volumes, but 7 mL suits standard lab pipettes accurately
- Forgetting units (all in mL here) or reversing concentrations leads to 50-fold errors—always confirm \(C_1 > C_2\)
- Two-step dilutions help precision for extreme factors, though unnecessary for 50X to 1X
CSIR NET Exam Tips
Practice similar dilution problems from past papers, as they test quantitative skills in biotechnology sections[web:11]. Memorize: volume of stock = final volume ÷ fold concentration. Use calculators like Sigma-Aldrich’s for verification during prep.
