<p>Yeah that question was #59 on the National Chemistry Olympiad, I was just doing a practice and thought I would post it.</p>
<p>is anybody not using their prep book to study for the ap chem test? I have barron’s and I can’t seem to read it without falling asleep so I’m just solving mc questions and studying that way. How is everybody else studying?</p>
<p>Im doing chem olympiad questions for practice.
I also reviewed some net ionics as well.</p>
<p>^overkill. total overkill.</p>
<p>Calm down. Its for a good cause</p>
<p>I plan getting 60% (or whatever the minimum percentage is) and getting a 5.</p>
<p>Wth is this enthalpy stuff and heat of formation etc. etc. / do we have to calculate anything dealing with specific heats or enthalpies of formation or whatever on the exam?</p>
<p>Yes. Absolutely.</p>
<p>Yup. 10char</p>
<p>but they give you the specific heats right? even for water, so you don’t have to memorize them</p>
<p>Yeah, they do. Water is something like 4.186 (don’t ask why I know that), but they should give you that too.</p>
<p>Alright very cool. </p>
<p>and i have a few more questions… </p>
<p>Can anybody explain why the answer is N2O in this question? </p>
<p>Which of the following oxides is a gas at 25C </p>
<p>a) Rb2O
b) N2O
c) Na2O2
D) SiO2
e) La2O3</p>
<p>annd one more</p>
<p>Which of the following must be true for a reaction for which the activation energy is the same for both the forward and reverse reactions? </p>
<p>a) a catalyst is present
b) The reaction order can be obtained directly from the balanced equation
c) The reaction order is zero
d) Delta H for the reaction is 0
e) Delta S for the reaction is 0 </p>
<p>The answer is (d) when delta H for the reaction is zero. can somebody explain this one to me as well</p>
<p>That’s just common sense, in my opinion lol. </p>
<p>If you didn’t know that N2O = nitrous oxide, you should commit that to memory. I’m pretty sure this is laughing gas haha.</p>
<p>Second one:
Delta H is a measure of heat transfer. If the same amount of heat is transferred in both the forward and reverse reactions, then then the activation energy is the same (same amount of heat added). Of course, one of the values will be negative and one will be positive.</p>
<p>^Well, honestly, that’s just something you have to know. N2O is a commonly found primary air pollutant in the atmosphere.</p>
<p>And delta H has to be zero, as otherwise there would be a fluctuation in activation energy.</p>
<p>@yo6522 SiO2 or silicon dioxide, or quartz, is also a network solid.</p>
<p>ok that clears things up tons
and also I guess this is a general (probably dumb haha) question but when delta H is equal to 0, what does that mean for the reaction?</p>
<p>edit: wait nvm, I somehow skimped over the answers for my second question. ok i get what happens now thanks everybody!!</p>
<p>Did anyone notice the organic chemistry in the m/c?..My teacher said it wasn’t on the exam…</p>
<p>Your teacher was mistaken. Orgo is on the exam, but there is usually no more than 1-2 questions on it.</p>
<p>Great…GREAT…</p>