<p>How do you do this type of problem? Can someone please simplify the steps for me? My textbooks explanation is very confusing, and my teacher did not teach this.</p>
<p>8.44 Which compound in each of the following pairs of ionic substances has the most exothermic lattice energy? Justify your answers.</p>
<p>a. LiF, CsF
b. NaBr, NaI
c. BaCl2, BaO
d. Na2SO4, CaSO4
e. KF, K2O
f. Li2O, Na2S</p>
<p>lattice energy is the change in energy that takes place when separated gaseous ions are apcked together to form an ionic solid. normally, the lattice enrgy can be calulated if the enthalpy values of certain elementary steps are given. however, in this problem, where no numbers are provided, you just have to use information about what affects lattice energy to determine which is more exothermic</p>
<p>difference in charges between the ions affects the latice energy more than the size of the ion does (the larger charge difference, the more exothermic, and the smaller the ions are, the more exothermic), so in your first example, LiF vs. CsF, Li and Cs both have a +1 charge, so ionic size must be considered instead. as one goes down the periodic table, the trend is that atomic radius increases because of more electron orbitals, meaning Cs+1 is larger than Li+1, and therfore the lattice energy of CsF is more exothermic</p>
<p>hope that helps ^</p>
<p>adam_dewitt7’s reply is exactly correct until the last line. Since Cs is larger than Li, the denominator of the lattice energy term (distance) is larger and the resulting lattice energy is a smaller negative number (less exothermic).</p>
<p>You said that, “the denominator of the lattice energy term…” Does this mean that there is an equation I can look at to determine the answer?</p>
<p>perhaps it is: (+q x -q)/r^2 where q refers the magnitude of charge and r = dist. between charges</p>
<p>thanks for correcting me gfaith. after reading my explanation’s last line, i realized i mixed it up and said the exact opposite.</p>
<p>and btw, the equation is:</p>
<p>lattice energy = k((Q1 x Q2)/r)</p>
<p>k= constant Q1 and Q2 are the charges, and r =distance</p>
<p>What book are you guys using or recommend to study for the Chem AP?</p>
<p>Im using Barron’s, and its pretty damn good, but my teacher recommends PR</p>
<p>yeah, my teacher recommends PR too, but I have been reading that the new Peterson’s Master Series (continuation of the ARCO series) is the best because it has really hard exams and it is really in depth, so when you’re taking the actual AP exam it is a peice of cake compared to the ones in the book.</p>
<p>I’m using Zumdahl and probably won’t get through enough material for the AP exam. Will it be a good idea to study PR and learn those topics? Would that be enough for a 5 assuming I understand all the problems in PR book?</p>
<p>I guess if you get 5’s one the practice exams in the packet, and hopefully by some margin (for safety), then you should be fine. My AP Chem teacher told us that A LOT of people get 5’s on the AP Chem and that it is probably the easiest science AP to get a 5 on. I think she said the hardest is AP Physics. </p>
<p>And by Zumdahl I guess you mean the textbook, and so here is another thing. I took some real practice AP exams, and I realized that many of the questions from it were very very similar to the questions in the very thorough textbook I’m using (Chemistry: The Central Science), so what I did was I bought used versions of the solutions booklet (about $15 all in all) to all the problems in the textbook and I have been practicing all the problems in it–and there are tons. I think this is an even better way to study for the AP then the prep books like PR, Barron’s, etc. But I would still recommend the prep books for the practice exams and test strategies.</p>
<p>you’re teacher is wrong, ap chem is not the easiest science ap lol. but w/e. usually just going over a prep book should be enough to at least pass, but try getting kaplans ap chem or the sat2 chem prep book to go over the concepts b/c its more comprehensive. the pr book only touches a bit on the different topics though its practice exams and pract probs are excellent</p>