how prepare 5L 0.3M acetate buffer,pH4.47,start fr 2M solution acetic acid & 2.5M solution KOH?

Answer 1

this is so easy, its WHACK

do you really not even know how to begin? or are you just testing me?

Answer 2

I guess this is homework, since in practice you would dissolve the proper amount of salt in some water and adjust the pH with a strong acid while monitoring it with a pH-meter.Then you add water to your final volume (it's a buffer so dilution doesn't affect pH)


All of your acetate moieties come from the CH3COOH solution.
So you would need V1=(C2/C1)V2=(0.3/2)*5= 0.75 L or 750 ml of the CH3COOH solution.

You should use the Henderson-Hasselbalch equation

pH=pKa+log([CH3COO-] / [CH3COOH])=
=pKa+log ([CH3COO-] / ([CH3COOH]total - [CH3COO-]))=
=pKa+ log (x/(0.3-x))

pKa=4.75

[CH3COO-] will be equal to the concentration of KOH in the 5L.
Solve the above equation and then you will need
V=(C'/C)V'=(x/2.5)*5 L of KOH solution.

In case you want to actually prepare it this way, mix most of the KOH solution that you calculated, but not all, with that of CH3COOH and then adjust the pH with the help of a pH-meter by adding slowly more KOH solution.