<p>is it really that bad?? :O</p>
<p>Does anyone know how to solve this problem from 2008 mc? I feel like it should be obvious but i’m not getting the right answer. answer key says it should be 11… "The pH of a solution prepared by the addition of 10 ml of .002M KOH to 10 ml of distilled water is closest to</p>
<p>@azes15 I couldn’t find the question…</p>
<p>@azes15 so, when you add 10 ml of distilled water to .002M KOH the concentration of the solution changes to .001 M. If you do .002M KOH* .01 L KOH to get the moles of KOH, you get .00002. The new total volume will be 20 mL due to the 10ml so if you divide that out, you get a new concentration of .001. Since KOH will completely disassociate, the concentration of KOH we calculated will be the same as [OH-] concentration. If we take the POH by taking the -log([OH-]), you get a POH of 3. To convert this to PH we need to use the formula 14 = PH + POH, and thus the answer is a PH of 11.</p>
<p>I’m getting nervous for the exam. I know everything I need to but still feel unprepared (especially for the lab question). I found the practice exam to be insanely easy for the MC section but I didn’t do that well on the FRQ. Also, I’m worried how bad the curve will be with the new exam (points to new Bio curve).</p>
<p>I have a question as well, my teacher gave us a practice test, but some of her answers are a bit incorrect, I would like to check with one of you guys. She left for a surgery this week so we cannot ask her questions since she was not here this week. So the question is, what is the largest species present when a weak acid goes to equilibrium. The choices are a. HA b. A- c. H3O+ and d. OH-. I thought that it was HA since weak acids do not disassociate much so they will be left while only a tiny amount of conjugate acid and H+ form. Other information that is given is that at a concentration of 1M, the PH of this weak acid is 2.44. Thanks for your help!</p>
<p>Yes, the answer should be HA. The Ka for a weak acid is less than one, and:</p>
<p>Ka = [H+][A-]/[HA]</p>
<p>If Ka is less than one that means there is a lot of HA. :)</p>
<p>Are we required to know about:</p>
<ul>
<li>Coordination compounds and complex ions</li>
<li>Lewis acid/bases</li>
</ul>
<p>we need to know coordination compounds/complex ions, but not a whole lot.
No lewis acid bases. only bronsted-lowry.</p>
<p>@DesiHero Thank you soo much!! I knew i was forgetting something - the new volume becoming 20 ml. As to your question, you are right about HA being present in the greatest amount</p>
<p>@kingofxbox99 That’s funny - I’ve been doing much better on the FRQs than the multiple choice (usually around 67%) My chemistry teacher says he thinks the curve should be similar to the past few years… I hope he is right. </p>
<p>@azes15 Did you try the released practice exam for 2014?</p>
<p>I think that they will curve it harder.
Also, thanks @kingofxbox99, my teacher put that it would be the conjugate base thats most abundant so I was a little confused. This question was from the practice exam for 2014.</p>
<p>@DesiHero I knew that question sounded familiar… :P</p>
<p>Anyone know approximately how much it was to get a 5 in previous years? Above like 65%?</p>
<p>i think it was between 63-67%</p>
<p>@kingofxbox99 Yeah I did and got about the same score (percentage-wise) as on the older exams. How did you do? I’m hoping that with strong FRQ responses (and an exam that’s not too terrible) I can get a 5. </p>
<p>@meaa7130 That’s good to know. Hopefully it doesn’t increase too much…</p>
<p>Hi, if someone could PM me the new AP Chem practice exam it would be a lifesaver. The link that was posted earlier isn’t working for me.</p>
<p>Thanks</p>
<p>@azes15 I got about 80% on the MC and I’m averaging low 70 for previous FRQ’s.</p>
<p>If there’s a harder curve I hope the questions are easier like on the new AP Bio exam… and @kingofxbox99 with that multiple choice score it would be hard to believe if you weren’t in the 5 range… I’m jealous! </p>