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Topic: Concentrations  (Read 5440 times)

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Offline soupastupid

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Concentrations
« on: October 14, 2008, 08:30:32 PM »
i don't know how to do this problem.

Offline soupastupid

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Re: Concentrations
« Reply #1 on: October 14, 2008, 09:48:14 PM »
is it

Cl = .220
C6H5NH2 = 2.18*10^-1
H3O+ = 4.21*10^-12
OH- = 2.38*10^-3
C6H5NH3+ = 2.38*10^-3

Offline enahs

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Re: Concentrations
« Reply #2 on: October 14, 2008, 10:05:45 PM »
You have to know some sort of dissociation constants. Were these given or did you look them up?
Or how did you come up with your numbers?


Offline soupastupid

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Re: Concentrations
« Reply #3 on: October 14, 2008, 10:35:26 PM »
i used

kw = 1*10^-14
kbase of C6H5NH3Cl = 3.9*10^-10

was i suppose to use those values?
and then i set up an ICE BOX

do u kno wat that is?

its hard to explain what i did

nevermind

i think i got it

tanx anyway

Offline Borek

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Re: Concentrations
« Reply #4 on: October 15, 2008, 05:20:21 AM »
H3O+ = 4.21*10^-12
OH- = 2.38*10^-3

Think it over.
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Offline soupastupid

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Re: Concentrations
« Reply #5 on: October 15, 2008, 06:24:43 PM »
think it over?

im assuming Cl is counterion right?

and so the equation becomes

C6H5NH2 + H2O = C6H5NH3+ + OH-

.220 for initial C6H5NH2 and Cl

and i put

(kw/ka)*(.220) = x^2

kw = 1*10^-14
kbase of C6H5NH3Cl = 3.9*10^-10

i get x = 2.38*10^-3
x= [OH-] and [H3O+] = kw/[OH-]
[H3O+] = 4.21*10^-12


this is wrong?
wat should i do?

Offline Borek

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Re: Concentrations
« Reply #6 on: October 15, 2008, 07:07:29 PM »
[H3O+] = 4.21*10^-12

Protonated aniline is a weak acid, yet you have calculated that the solution is basic.

What are initial species in the solution?
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Offline soupastupid

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Re: Concentrations
« Reply #7 on: October 15, 2008, 09:42:45 PM »
initial species?

i think its suppose to be base

intial species of Aniline

C6H5NH2 and H20
there is .220 M of aniline because Cl is a counterion (how do I know its a counterion? im just guessing it is)

this makes C6H5NH3+ and OH-

right?

Offline Borek

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Re: Concentrations
« Reply #8 on: October 16, 2008, 03:49:25 AM »
No, you start with aniline hydrochloride, that means aniline was fully protonated.

Think: why should aniline (neutral molecule) need counter ion?
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