SOLUTION: Given a stock solution of 5.0% sodium chloride (NaCl), how would you prepare 20 ml of a 2.0% sodium chloride solution? (I have tried many of the examples you give others but I can'

Question 498280: Given a stock solution of 5.0% sodium chloride (NaCl), how would you prepare 20 ml of a 2.0% sodium chloride solution? (I have tried many of the examples you give others but I can't work it out for some reason.)
Answer by josmiceli(19441) (Show Source): You can put this solution on YOUR website!
In words:
(ml of NaCl you end up with) / (ml of total solution you end up with) = 2%
They are not telling you how many ml of the stock solution you start with.
They only say you end up with 20 ml of solution.
In order to get down from 5% to 2% you must add water ( or whatever the solvent is)
They should have mentioned that
Let = ml of the 5% solution you need
Let = ml of water to add
given:
= NaCl in the 5% solution
(1)
---------------
(2)
(2)
(2)
and, since
(1)
(1)
(1)
You need 8 ml of the 5% solution
and 12 ml of water
check:
(2)
(2)
(2)
(2)
OK
RELATED QUESTIONS
How much sodium chloride is needed to make 325 ml of a 20 percent w/v solution in... (answered by jorel555)

For an experiment, a student requires milliliters of a solution that is NaCl (sodium... (answered by richard1234)

A sample of seawater contains 6.0277g sodium chloride per liter of solution. How many mg (answered by scott8148)

A chemist has 100 liters of 20% sodium chloride solution. She intends to drain a certain... (answered by richwmiller)

A chemist has 100 liters of 20% sodium chloride solution. She intends to drain a certain... (answered by TimothyLamb)

THREE HUNDRDE MILLILITES FO A 5% NAC1 SOLUTION IS NEEDED. HOWEVER ONLY A 10% SOLUTION OF... (answered by mananth)

A chemist needs a saline solution that is 20% sodium chloride but only has solutions that (answered by checkley77)

For an experiment, a student requires 200 milliliters of a solution that is 8% NaCl... (answered by Alan3354,stanbon)

For an experiment, a student requires 200 milliliters of a solution that is 12 % NaCl... (answered by josmiceli)