Posted by Sarah on .
Strychnine, C21H22N2)2(aq) is a weak base but a powerful poison. Calculate the pH of a 0.001 mol/L solution of strychnine. The Kb of strychnine is 1.0 x 10^6
DrBob222, I am planning on obtaining a pHD in about nine years:P Can you give me some advice on how to be that 1% of the population who has a pHD?
chemistry  DrBob222, Sunday, April 6, 2008 at 12:38am
Start now!
Let's call strychnine SN.
SN + HOH ==> SNH^+ + OH^
Kb = (SNH^+)(OH^)/(SN)
(SNH^+) = x
(OH^) = x
(SN) = 0.001  x
Plug into Kb and solve for x = (OH^)
pOH =  log(OH^)
and pH = 14  pOH
Kb = (SNH^+)(OH^)/(SN)
= (x)(x) / 0.001  x
= x^2 / 0.001  x
How is the next step supposed to look?

chemistry 
DrBob222,
Kb = (SNH^+)(OH^)/(SN)
= (x)(x) / 0.001  x
= x^2 / 0.001  x
You haven't included Kb. Look in the problem, I know you posted it, and this last equation becomes
(x)(x)/(.001x) = Kb. After adding the Kb into the mix, this is a quadratic equation unless the 0.001x can be simplified to 0.001. 
chemistry 
Sarah,
(x)(x)/(.001x) = Kb
(x^2)/(0.001  x) = 1.0 x 10^6
So, in the form of ax^2 +bx + c = 0
this is
x^2 + 0.001x + 1.0 x 10^6? 
chemistry 
DrBob222,
See my later post to this question. But what you have written isn't correct.