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<div class="moz-cite-prefix">From step 1 the hydronium ion
concentration was 0.0397. In the second and third equilibrations
I would calculate x values that had to be ADDED to 0.0397 to get
the total hydronium ion concentration. In step two that value was
0.0000000625. In the third step it would have been even smaller
based on the relative size of Ka3. Since both of these are
insignificant compared to 0.0397, I just based the pH off of the
0.0397.<br>
<br>
You cannot always assume that the other steps are insignificant
but you can assume that if the second step is insignificant then
the third step is insignificant too.<br>
<br>
<br>
On 07/21/13 21:01, Mary Caroline Logan wrote:<br>
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<div>For question number 16.84: after you calculate the
concentrations of the second reaction, why did you stop? Is it a
general rule that if x is insignificant in comparison to the x
of the previous reaction, then you stop? I'm confused. I
continued on and calculated the third x the same way I had
before with the Ka3, and I ended up with a ph of 7.2, which
seemed way too high. <br>
<br>
Caroline Logan</div>
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<pre class="moz-signature" cols="72">--
Andrew J. Pounds, Ph.D. (<a class="moz-txt-link-abbreviated" href="mailto:pounds_aj@mercer.edu">pounds_aj@mercer.edu</a>)
Professor of Chemistry and Computer Science
Mercer University, Macon, GA 31207 (478) 301-5627
<a class="moz-txt-link-freetext" href="http://faculty.mercer.edu/pounds_aj">http://faculty.mercer.edu/pounds_aj</a>
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