Final answer:
To make 100mL of a 4% solution from a 20% stock solution, you need to add 80 mL of sterile diluent to 20 mL of the stock solution.
Step-by-step explanation:
To calculate how much sterile diluent to add to make 100mL of a 4% solution from a 20% stock solution, we use the dilution equation C1V1 = C2V2, where C1 and V1 are the concentration and volume of the stock solution, respectively, and C2 and V2 are the concentration and volume of the final diluted solution, respectively.
In this case, we have the following:
- C1 (stock concentration) = 20%
- C2 (final concentration) = 4%
- V2 (final volume) = 100 mL
First, rearrange the equation to solve for V1:
V1 = (C2V2) / C1
Substitute the known values into the equation:
V1 = (4% × 100 mL) / 20%
V1 = (0.04 × 100 mL) / 0.20
V1 = 4 mL / 0.20
V1 = 20 mL of 20% stock solution are needed.
To find the amount of sterile diluent required, subtract the volume of the stock solution from the final total volume:
Sterile diluent volume = V2 - V1
Sterile diluent volume = 100 mL - 20 mL
Sterile diluent volume = 80 mL
Therefore, you need to add 80 mL of sterile diluent to 20 mL of the 20% stock solution to make a total of 100 mL of a 4% solution.