<p>Do we have to know how to calculate the pH of buffers using some weird law? And for that matter, must we be able to calculate pH of any acid and solution if it’s just in a reaction?</p>
<p>any question concerning pH should be laughably easy…</p>
<p>for example, the BB asks… a solution with a pH of 6 is:
neutral? umm no.
very acidic? umm no.
slightly basic? Nah.
very basic? no…
slightly acidic? yes!!!</p>
<p>tough one right?</p>
<p>I think they’re more along the lines of changing a figure for [H+] into a pH (like .00001 would be a pH of 5).</p>
<p>Why is the answer (B) for this one? (from collegeboard)</p>
<p>An active ingredient in common household bleach solutions is most likely to be which of the following?</p>
<p>A. NaCl (of course not)
B. NaClO (hypochlorite? :/)
C. NaHCO3 (it would make a basic solution…)
D. Na2SO4 (no, it would be a neutral solution)
E. HC2H3O2 (no, that’s acetic acid.)</p>
<p>I was stuck between B and C and went with C because i’ve never seen hypochlorite in a compound before. :(</p>
<p>chlorine is often used as a cleaning agent and a salt of hypochlorite is used in bleach</p>
<p>I am taking the test tomorrow. With only Honors Chemistry, am I screwed?</p>
<p>You know, I adore the Barrons test prep company, but I’m a little annoyed at the low quality of the practice tests in the back of their SAT II Chemistry. First of all they have a scale that makes it impossible to get an 800 - the maximum number of points is 69, and the raw score scale goes up to 85. But what really gets to me is the imprecision of many of the TTCE questions. Often, as someone mentioned earlier, their choice of whether or not to include the CE seemed somewhat arbitrary, and either position could be argued. And then of course there’s their penchant for asking you about topics that seem randomly pulled out of some hat into which all kinds of facts have been indiscriminately tossed. Lol.</p>
<p>And their obsession with thistle tubes is kind of depressing.</p>
<p>But I still love the book.</p>
<p>Sparknotes seriously needs to check its tests for errors. On the third test, questions 64-66 tell you to refer to the heating curve. The problem is that THERE IS NO GRAPH. And on the second test, there is a I II III IV question about decreasing electronegativities, and it says that I<Br<Cl<F is wrong, but electronegativity decreases as you move down the periodic table.</p>
<p>And I agree, the TTCE questions are so confusing. I can answer each question separately to see if each statement is true or false, but the CE throws me off. Here’s a question example: Water has high melting and boiling points BECAUSE hydrogen bonds are strong intermolecular forces. Both statements are true, but neither statement indicates that intermolecular forces result in high melting and boiling points. If I were an English teacher I would say TT, but if I were a Chemist who considered it to be common knowledge I would say TTCE. It’s so confusing…I hope a lot of the questions have Fs in them.</p>
<p>I’ve studied all week long and my practice test scores have gone down and only slightly come up. I got a 780 barely studying, and a 650 on Wednesday! I should just start looking for four-leaf clovers now because I’m going to need a lot of LUCK.</p>
<p>^ I agree. Sparknotes really ****ed me off today. They have HORRIBLE questions</p>
<p>I thought Kf and Kb vary for different substances? are those constants for water? and I read Kaplan’s, and it doesn’t mention it at all, so probably not. I agree with Buzzer11’s and dunbar’s points.</p>
<p>yeah, Kf and Kb are substance-specific, and constants. I’ve only ever seen them used for water, but CB could hypothetically ask questions about a different liquid. I’d expect them to give you the values, though.</p>
<p>Question: in a voltaic cell, is the anode positive, and the cathode negative? or is it the other way around? I’ve seen it both ways in a number of prep books. </p>
<p>and I agree, Sparknotes is screwed up</p>
<p>DFactorial, the tests only go up to 69 because there are the true false questions in the middle that start at a hundred, if you add them together, you get 80</p>
<p>yea, i see it different in different books; this is my reasoning: anode is oxidation and cathode is reduction and so electrons move from anode to cathode and cations move towards the cathode and anions move toward to anode, thus i think cathode must be negative to attract the cations</p>
<p>^indeed. good night everyone and good luck… lets see those 800s</p>
<p>actually, in a voltaic cell
i believe the cathode is positive and anode is negative</p>
<p>Good luck. I’m not super-confident, but at least I can retake them!</p>
<p>Barron’s says that the “charge” of the electrodes varies from experiment to experiment. So I wouldn’t worry about that (unlikely to show up) and just use common sense in the rare instance that it’s asked.</p>
<p>Could anybody explain questions 4, 5, and 6 on the Blue Book?</p>
<p>Those are tricky ones</p>
<p>4 and 5 use this equation
Na2CrO4 + Pb(NO3)2 –> PbCrO4 + 2NaNO3</p>
<ol>
<li><p>A yellow solid forms, PbCrO4, as the result of the double replacement reaction. The question remains whether any CrO4 2- will remain in solution, making the solution yellow. 1 mol Na2CrO4 has 1 mol CrO4 2- which is all used up since we have more than enough Pb 2+ (2 mol). All the CrO4 2- is present as precipitate, the solution is colorless.</p></li>
<li><p>Again, a yellow solid forms. However, we now have 3 mol CrO4 2- and only 1 mol Pb 2+. 2 mol CrO4 2- will be left in solution, making it yellow.</p></li>
<li><p>This is the easiest one. NaNO3 and Pb(NO3)2 are unchanged because switching their anions would yield the same species. Both are soluble (no solid formed) and there’s no CrO4 2- to color the solution, so the solution is colorless.</p></li>
</ol>