Question

How much stock solution is needed to prepare a 20 ml 1:4 dilution of a stock solution?

1) 5 ml
2) 10 ml
3) 15 ml
4) 20 ml

Answer 1

To make a 20 ml 1:4 dilution from a stock solution, divide 20 ml by the dilution factor of 4, resulting in 5 ml of stock solution needed.

Step-by-step explanation:

To prepare a 1:4 dilution from a stock solution, you need one part stock solution to three parts diluent (typically water), making a total of four parts. In this specific dilution, you require 20 ml of final volume. To find the volume of stock solution needed, divide the total final volume by the dilution factor (4 in this case). So, you divide 20 ml by 4, which equals 5 ml of stock solution.

The step-by-step process involves:

1. Determining the final volume needed, which is 20 ml.
2. Dividing this volume by the dilution factor, 20 ml ÷ 4 = 5 ml.
3. Measuring 5 ml of the stock solution.
4. Add this to sufficient solvent to reach the final volume of 20 ml.