pka - Biology Forum

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2468 11 years, 11 months ago

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- November 30, 2012 at 10:45 pm #17103
  2468
  Participant
  Hey, 🙂
  need help working this out:
  pH: 4
  molar extinction coefficient: 0.0187142857 m-1cm-1
  absorbance at 500nm: 1.492
  [Acid form]?? (work out using molar extinction coefficient)
  [base form]?
  lg([acid]/[base])?
  pKa?
  If someone can guide me on how to do this especially the acid form….i’d greatly appreciate it…so i can use the basics fr it to work out the rest of my ques…
  thank you
- December 1, 2012 at 5:44 pm #113152
  JackBean
  Participant
  don’t you need more values?
- December 1, 2012 at 5:58 pm #113153
  2468
  Participant
  quote JackBean:
  don’t you need more values?
  oh yeah sorry and methyl red concentration was 12.5um….3ml of buffer used and 1ml of stock methyl red..if that helps?…really cant get my head round this..i’ve tried searching
- December 1, 2012 at 6:18 pm #113154
  JackBean
  Participant
  LOL, you’re really expert.
  From Lambert-Beer law (A = e.c.l) calculate concentration of the color form. Concentration of colorless form is c(total) – c(color)
- December 1, 2012 at 6:25 pm #113155
  2468
  Participant
  quote JackBean:
  LOL, you’re really expert.
  From Lambert-Beer law (A = e.c.l) calculate concentration of the color form. Concentration of colorless form is c(total) – c(color)
  ‘Love’ the sarcasm.. :/
  Elaborate? Dont undertsand it.
- December 1, 2012 at 11:46 pm #113158
  JackBean
  Participant
  This could be of use for you
  http://www.usca.edu/chemistry/spectra/methlred.htm (if you can open *.spc files)
  http://www.colby.edu/chemistry/PChem/la … hylRed.pdf (especially picture on p. 3 where you can see that the extinction coefficient is around 8000 M-1 cm-1)
  http://www-ec.njit.edu/~grow/Methylred.pdf
- December 4, 2012 at 1:06 am #113174
  2468
  Participant
  Thank you! 😀
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