How would you prepare 500ml of 28% w/v (weight/volume) KOH (potassium hydroxide) solution? From this stock, how would you prepare a 0.1M working solution?
"m(KOH)=500\\ ml\\ *\\ 0.28\\ w\/v=140\\ g"
"n(KOH)=\\dfrac{Mass}{Molar\\ mass}=\\dfrac{140\\ g}{56\\ g\/mol}=2.5\\ mol"
"c(KOH)=\\dfrac{Moles}{Volume}=\\dfrac{2.5\\ mol}{0.5\\ L}=5M"
To prepare a 0.1M solution we need to dilute "\\dfrac{5M}{0.1M}=50"-fold with water. If 500 mL of working solution is needed, then "\\dfrac{500\\ mL}{50}=10\\ mL" of the stock solution should be diluted with water to 500 mL.
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