Question #17770
1 Answer
Explanation:
The idea here is that you're diluting an initial
As you know, when you're diluting a solution, the ratio that exists between the concentration of the stock solution and that of the diluted solution si equal to the ratio that exists between the volume of the diluted solution and that of the stock solution.
This means that you have
#"DF" = V_"diluted"/V_"stock" = c_"stock"/c_"diluted" -># the dilution factor
In your case, the concentration of the solution decreases by a factor of
#"DF" = (50 color(red)(cancel(color(black)("ppm"))))/(20color(red)(cancel(color(black)("ppm")))) = color(blue)(2.5)#
which implies that the volume of the stock solution must be
You will thus have
#V_"stock" = V_"diluted"/color(blue)(2.5)#
which gets you
#V_"stock" = "100 mL"/color(blue)(2.5) = color(darkgreen)(ul(color(black)("40 mL")))#
The answer is rounded to one significant figure.
