Question

Question #cceac

Answer 1

`"400 mL"`

Explanation:

The idea here is that the ratio that exists between the concentration of the stock solution and the concentration of the diluted solution is equal to the dilution factor.

Moreover, the dilution factor is also equal to the ratio that exists between the volume of the diluted solution and the volume of the stock solution.

In your case, the dilution factor is equal to

`"DF" = (5 color(red)(cancel(color(black)(%))))/(4color(red)(cancel(color(black)(%)))) = color(blue)(1.25)`

This means that the volume of the diluted solution will be `color(blue)(1.25)` times bigger than the volume of the stock solution.

`color(blue)(1.25) = V_"diluted"/V_"stock" implies V_"stock" = V_"diluted"/color(blue)(1.25)`

In your case, the volume of the stock solution will be equal to

`V_"stock" = "500 mL"/color(blue)(1.25) = color(darkgreen)(ul(color(black)("400 mL")))`

The answer is rounded to one significant figure.

So, in order to prepare your solution, you would take `"400 mL"` of the `5%` stock solution and add enough water to get the total volume to `"500 mL"`.