In: Chemistry
prepare 200mL of a 6% w/v NaOH solution from stock NaOH (FW 40)
formula weight(FW) of NaOH is 40 gm/mole
6% w/v NaOH solution means 6 gm NaOH remains in 100 ml soltion.
so 200 ml solution contains = 6 * 2 = 12 gm NaOH.
6 gm NaOH = mass / molar mass = 6.00/40 = 0.15 mole
concetration of NaOH in 6% solution = 0.15*1000 / 100 = 1.5 M
If stock solution of NaOH concentration is 2.0 M
then using simple dilution law,
V1*S1 (stock soltion)= V2S2 (after dilution)
V1 * 2.0 = 200 * 1.5
V1 = 150 ml.
so volume of stock solution take 150 ml and mixed with adding (200-150) = 50 ml water.
otherwise,
200 ml water take in which 6*2 = 12 gm NaOH solid is added to prepare 200 ml 6% NaOH solution.