If

The charge balance and proton condition, with H20 and HAc being the reference specjifc.v are identical: ... .'u-: . •. '■•;• ■ "•

I/--/:: ' ['};■ ■ ' ;-f. ':•":. [H+] = [OHI + [AC] .' '.7

y From the assumption noted above ([H+] [OH~]), the charge balance reduces to ' 'I-/ '

¿^r■ ' i'7 ■•. . • [H+J = [Ac-]/'i;'7 v."S

; If we let x = [H+] = (Ac"] and note from the mass balance on acetic acid that [HAc] = ? 0.01 - x,wp can substitute into the equilibrium relationship for acetic acid: : . ■

' Multiplying through and rearranging terms yields js2 + 1.8 X 10"sx — 1.8 X 10~7 = 0 V

This equation can be solved using the quadratic formula: i

-(1.8 X 1Q"5) ± Vq.8 x IP-5)2 - 4(1)(—1.8 X 10-Q

Thus, [H+] = 4.15 X 10~", or pH = 3.38. This is the same answer pbtained in'Example . ! 4 2 when simplifying assumptions were not used

;: It is clear that since pH =,3.38, our assumption that [H1] is much greater than [QHr] is a good one The second assumption that [HAc] is greater than [Ac-] is also a good one :'since [Ac-] = 4:14 X 10"4. From the mass balance on acetic acid: . ■■ "v:;;..^j*'J

; [HAc] = 0.01 - 4.14 X 10"4 = 9.59 X IP"3_

collections.' The strident should note that NaCl completely ionizes upon addition to water. For this problem, the equilibrium relationships are

I: The mass balance relationships are .';

Qhac = 0.01 = [HAc] + [Ac"] '; ■ , ' Cr.Na = 0.01 = [Na*] :. ."Vh. 'V: : .ct - °-01 = [en ■ v.": :-v'-

'[H+] + [Na+] = [OH"] + [Ac~] + [cr] ; . ■ . . :

Was this article helpful?

0 0
Healthy Chemistry For Optimal Health

Healthy Chemistry For Optimal Health

Thousands Have Used Chemicals To Improve Their Medical Condition. This Book Is one Of The Most Valuable Resources In The World When It Comes To Chemicals. Not All Chemicals Are Harmful For Your Body – Find Out Those That Helps To Maintain Your Health.

Get My Free Ebook


Post a comment