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Topic: buffers problem  (Read 5643 times)

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Offline govibe

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buffers problem
« on: January 06, 2008, 06:20:31 PM »
"Calculate the pH after 0.020 mol NaOH is added to 1.00 L of each of the following solutions.

    (a) 0.480 HONH2 (Kb = 1.1x10-8)
    (b) 0.480 M HONH3Cl
    (c) a mixture containing 0.480 M HONH2 and 0.480 M HONH3Cl"

for (a), the reaction, the dissociation is HONH2+ H2O --->>> H4ON+ + OH- ??
The ICE box is like

HONH2+ H2O --->>> H4ON+ + OH-
0.480M                     0         0.02
-x                            +x        +x

so the Kb=1.1E-8 = (0.02+x)x/(0.480-x)

so x is 2.64E-7, so OH- concentration is 0.02+2.64E-7=0.02. The negative log of that is 1.7, and 14-1.7 is 12.30, is that correct? Do I have to do a stoichiometry equation in eddition to an ICE box?

for parts b and c, I'm not sure the dissociation of HONH3Cl is...

Offline Borek

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Re: buffers problem
« Reply #1 on: January 06, 2008, 06:57:12 PM »
So your main problem is whether hydroxylamine is basic or acidic... It is basic, it can get protonated like ammonia.
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Offline govibe

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Re: buffers problem
« Reply #2 on: January 06, 2008, 07:37:15 PM »
what does the salt HONH3Cl dissociate into?

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