<p>Quick question: Is the heat of vaporization ALWAYS greater than the heat of fusion? If so, WHY?</p>
<p>i needz some helpz with ma qz.
alright so there was this one question in barrons about which solution has the highest boiling point. i was going with NaCl but the answer was CaCl2. after reading the explanation it makes complete sense but then i was thinking about what if there was a covalently bonded(covalent bonded molecules are nonpolar right?) with the same amount of ‘ions’. would say something like XY2 have the same BP? probably not right? also just curious but what has the higher BP? h2so4 or CaCl2?</p>
<p>@lancelotdulac:</p>
<p>i was thinking about ur question and i came up with this:</p>
<p>Heat of vaporization is essentially just going from liquid to gas. H of fusion is essentially solid to liquid. basically what i like to think is that as the temperature increases the bonds between molecules seperate right? in a solid you need quite a bit of enthalpy to seperate it into liquid. But in the case of liquid to gas, u break apart a lot more IM forces. i believe that IM forces require way more energy to seperate.</p>
<p>idk its hard to explain.</p>
<p>ALSO: i took ap chem this year. what were some things that were covered on the subject test that isn’t on the AP? i am going through practice tests atm to review what i have forgotten.</p>
<p>another question. easiest way to memorize the oxidation states of metals?</p>
<p>er… the only ones you need to know chickenonrice are that ag+1 zn +2 al +3, etc. you don’t really need to know the others…</p>
<p>ight cool. could u help me with the question like 3 above?</p>
<p>also um how much in detail should one know first ionization, 2nd and 3rd?
also ummmm electron affinity?</p>
<p>also for Ksp problems do u guys normally round and stuff cause if ur pressed for time how would u do exact calcs…</p>
<p>cause i got basically all the computation questions wrong cause i saved them for last but i was running out of timeD:</p>
<p>Oxidation states of metals? You should know that if you took ap chem…
Know the trends for ionization energies.
Since you don’t have a calculator, all the math is easy. Really easy.</p>
<p>nah man like one question in barrons gave us a chart with Sulfur on it and gave us a bunch of letters on a periodic table and asked which one would make a 1:1 ratio type of compound. i was like ***? i was like um… ima assume this is going to be ionic and i limited it down to 2 choices but i didn’t know the oxidations for Mg and the other one(i think it was Ba) and i lost an easy point…</p>
<p>What’s the relationship between a boiling point and vapor pressure? i dont really get the difference between the two…</p>
<p>Oh and does anyone know where i can find good descriptive chemistry info? Or any general chemistry info that will help me answer questions like “what is the element most commonly used in fertilizers”</p>
<p>@Lovex,
Knowing the background information sometimes helps:</p>
<p>Haber, a German chemist, used the “Haber Process” (N2 + 3H2 –> 2NH3) during the first World War to create ammonia, which is commonly used in fertilizers. He later earned a Nobel Prize for his work.</p>
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<p>I’d say that oxidation states for all elements would be their charges in an ionic compound. So Na would be +1, Cl would be -1, etc. The weird oxidation states come with transition metals.</p>
<p>@lovex: boiling point is associated with vapor pressure because when a molecule’s bonds are stronger, vapor pressure tends to be low and boiling point high (essentially the boiling point is when vapor pressure = atmospheric pressure). Also when you go up in the mountains (correct me if I’m wrong) but atmospheric pressure decreases, therefore boiling point can be achieved easily (since vapor pressure can easily meet the atmospheric pressure) so it takes longer for an egg to cook.
If what I said makes absolutely no sense, this guy does a good job of explaining it: [YouTube</a> - Vapor Pressure and Boiling](<a href=“Vapor Pressure and Boiling - YouTube”>Vapor Pressure and Boiling - YouTube)</p>
<p>I have a kind of a dumb question, but if the melting point is “low” does that mean the IMF are very strong? (i.e. it would have a high boiling point, etc.)</p>
<p>How does the subject test compare in difficulty to the AP Chem test? I had a great teacher the past two years for chem and I thought the AP test was pretty easy.</p>
<p>^Easier. T,T,CE is just a different question format that you need to be comfortable with.</p>
<p>Is it weird that I feel more comfortable with the T,T,CE questions than any other part of the test?</p>
<p>According to Barrons, I’m going to get a 560… Exciting.</p>
<p>Do diagrams about the electrolytic cells (anode cathode battery etc) and silver plating come out frequently? The whole chapter and redox-oxidation part is my weakness kind of… </p>
<p>Also how would you balance an equation using the half redox method? Correct me if I’m wrong about this… cause sometimes just doing it by sight or plugging in the answer choices will kill a lot of precious time…</p>
<p>do NOT let Barrons get you down!</p>