Category: Science > Chemistry
Asked by: medicine_man-ga
List Price: $9.00
19 Nov 2006 22:33 PST
Expires: 19 Dec 2006 22:33 PST
Question ID: 784171
What is the pH of a 0.062 mol L-1 solution of aniline (C6H5NH2) solution? Kb for this weak base is 4.2 x 10^-10. Please show me how you get to the pH :) Cheers.
Re: pH calculation
Answered By: livioflores-ga on 27 Nov 2006 21:29 PST
Hi!! For a base A that follows the equation: A?(aq) + H2O(l) <----> HA(aq) + OH?(aq) Kb = [HA]*[OH-]/[A-] For aniline the ionization equation is: C6H5NH2 + H2O <----> C6H5NH3+ + OH- Note that [OH-] = [C6H5NH3+], then for aniline: Kb = [OH-]^2/[C6H5NH2] Our first intermediate goal is to find the [OH-]: [OH-] = sqrt(Kb*[C6H5NH3+]) = = sqrt(4.2 x 10^-10*0.062) = = 5.103*10^-6 Now we can obtein the pOH, and with this we can get pH easily: pOH = -log[OH-] = 5.2922 pH = 14-pOH = 8.7078 For further references see: "Ionization Constants for Weak Bases": http://www2.austin.cc.tx.us/chemlab/weakbase.htm "Calculating the pH of Weak Acid and Base Solutions": http://dbhs.wvusd.k12.ca.us/webdocs/AcidBase/Weak-AcidBase-Practice.html "Acid dissociation constant - Wikipedia, the free encyclopedia": http://en.wikipedia.org/wiki/Acid_dissociation_constant "Chemistry: Acids and Bases": http://www.shodor.org/UNChem/basic/ab/ Search strategy: aniline "ionization equation" ph kb base ph calculation base I hope this helps you. Feel free to request for a clarifiation if you need it. Regards, livioflores-ga
rated this answer:
Excellent answer thanks a lot livioflores :)
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