Suppose you want to make a pH= 4.25 buffer. What would be thebest acid/base syst

Question

Suppose you want to make a pH= 4.25 buffer. What would be thebest acid/base system: acetate acid/acetate or lactic acid/lactate? TheKa of lactic acid is 8.32 x 10-4 ,Ka of acetc acid is 1.75 x10-5. Explain the answer? Any help with this would be appreciated. Promise to rate.K8 Suppose you want to make a pH= 4.25 buffer. What would be thebest acid/base system: acetate acid/acetate or lactic acid/lactate? TheKa of lactic acid is 8.32 x 10-4 ,Ka of acetc acid is 1.75 x10-5. Explain the answer? Any help with this would be appreciated. Promise to rate.K8

Explanation / Answer

Suppose you wanted to make a pH = 4.25 buffer. What would bethe best acid base system acetic acid/acetate or lactic acid/lactate? the Ka of lactic acid is 8.32 x 10^-4 and Ka ofacetic acid is 1.75 x 10^-5.

An ideal acid for a pH = 4.25 buffer, will have a pKa as close topH of 4.25 as you can find.
It is at the pKa that 50% of the moles are acid... to bufferagainst someone adding bases, & 50% of the moles are theconjugate ion base... to buffer against someone adding acids.

@ this point it has max buffering capicty in both directions,&

Ka = [H+][50%] / [50%], so Ka=H+ & pKa = pH+

Ka of lactic acid is 8.32 x 10^-4 .... & this has a pKa =3.08

and Ka of acetic acid is 1.75 x 10^-5... & this has a pKa =4.76

the closest best acid base system is acetic acid/acetate.

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