Question

A stock solution was diluted 1:5, then 1:3, then 1:2, and finally 1:6 to produce a final concentration of 0.4 mg/ml. The original concentration of the stock solution was...?

Answer 1

To find the original concentration of the stock solution, we can work backward through the dilution steps. By setting up an equation with the final concentration, we can solve for the original concentration.

Step-by-step explanation:

The original concentration of the stock solution can be calculated by working backward through the dilution steps. First, let's assume that the original concentration of the stock solution is C. After being diluted 1:5, the concentration becomes C/5. After being diluted 1:3, the concentration becomes (C/5)/3. After being diluted 1:2, the concentration becomes ((C/5)/3)/2. Finally, after being diluted 1:6, the concentration becomes (((C/5)/3)/2)/6.

We know that the final concentration of the solution is 0.4 mg/ml. Setting up an equation, we have (((C/5)/3)/2)/6 = 0.4. Solving for C, we find that the original concentration of the stock solution is 14.4 mg/ml.