***October 2013 - Chemistry***

<p>raw score of 65 is how many wrong given left 9 blank?</p>

<p>@actsat2400 raw score of 65 is 15 blank and 4 wrong
raw score of 65 is 9 blank and 9 wrong</p>

<p>btw, does anyone remember any True Trues (ik i said this b4 but my friend remember getting it for the water question)</p>

<p>@hopeisbeauty - Its an isolated system so no heat or mass can escape. As the vapor condenses back, its kinetic energy gets transferred to other molecules. The systems total K.E should remain constant. So temp is same.</p>

<p>Not T,T,CE :(</p>

<p>N2 is also Linear BUT they were asking for a POLAR LINEAR molecule.
N2 is not polar ( They share electrons equally ( Dipole moment = 0) ).</p>

<p>I remember hydrolysis being endothermic (T), and change of phase of water increasing entropy (T), but since hydrolysis is a chemical change and phase change is a physical change they didn’t CE. Like I said, there were a ridiculous amount of thermo questions imo. There were probably TTs but can’t remember.</p>

<p>It did have a surprising amount of thermodynamics questions. But mostly its just addition and subtraction. Here some of the questions I found annoying/difficult.
A sample of 45 grams of CxHy has 36 grams of C and 9 grams of H, which would be the empirical formula for the hydrocarbon? I put CH3, think because of the ratios were the same. (Foolish mistake, I put C2H3, whatever.) I’m at 1 wrong so far.</p>

<p>Then there was a question about sig figs, 20. ml of something was mixed with 4.07, something…, it was basically testing if you knew sig figs, I was stuck between 50. and 54, I put 54, really forgot sig figs. </p>

<p>I believe that T/F question was:
There is no color change in a reaction that is at equilibrium BECAUSE at the molecular level, there is are no changes. I believe I put F,F. </p>

<p>When water boils, the temperature of the water decreases BECAUSE molecules with higher KE and speed escape leaving molecules with lower KE and speed.
I put T,T,CE. I may be wrong.</p>

<p>Trollaunty wasn’t it an open container?</p>

<p>@trollaunty for that question, i agree with chessy on:
When water boils, the temperature of the water decreases BECAUSE molecules with higher KE and speed escape leaving molecules with lower KE and speed.
I put T,T,CE. </p>

<p>and i think it was an open container as well.</p>

<p>what did you guys get for that halogen oxide question? (it was a t/f)</p>

<p>@chessy I agree with you on the ff and ttce. I got confused on the sig figs question but now that I think about it I’m pretty sure 54 was right (ugh!). For the empirical formula question for CxHy it was CH3 because 36/12=3 mol and 9/1=9 mol. C3H9 reduced to empirical is CH3.</p>

<p>I believe it said:
All halogens are good oxidizers BECAUSE every halogen contains a sample of oxygen in them.
T,F. </p>

<p>There was a similar one deals with halogens.
HCl is a weak acid BECAUSE Chlorine is a very electronegative element.
I put F,F.</p>

<p>Electronegativity increases across periods and decreases down a group, and chlorine’s the second highest halogen, so I said that it was true that chlorine was very electronegative. I did put false for the HCl being a weak acid though.</p>

<p>Ugh I hope there is a nice curve for this test. </p>

<p>Chessy the halogen one had the statements the other way around but now that I think about it the one where they contain oxygen is definitely false. They almost always contain hydrogen…</p>

<p>@chessy Cl is a very electronegative element:
[Electronegativity</a> Table of the Elements](<a href=“http://www.tutor-homework.com/Chemistry_Help/electronegativity_table/electronegativity.html]Electronegativity”>Electronegativity Table of the Elements)</p>

<p>My teacher told me that only N,O,F are the very electronegative elements. Plus, if chlorine was very electronegative, HCl would be a weak acid. Since it would be difficult for H to dissociate from Cl. I think my reasoning is right, unless there is something else I’m missing.</p>

<p>Electronegativity mostly affects polarity. Cl is highly electronegative so HCl is very polar. HCl will dissociate completely in water since it is a strong acid so the weak acid part is false. As for whether highly electronegative compounds make weak acids, that’s an interesting though but it’s just elementary to know that HCl is strong. It’s FT I believe.</p>

<p>@Chessy N, O, and F are the only very electronegative elements that account for hydrogen bonding.</p>

<p>Fine, fine. I guess you are right. Definitely 2 wrong now.</p>

<p>t/f questions I rmr:
-electrolysis of water
-CH4 square planar
-catalysts reaction mechanism
-water boil, lower temp
-organic chem same structure ques
-halogen oxides
-color equilibrium
-Na K reaction with water
-Na K Li similar properties
-hcl and cl electronegativity question
-H20 not linear molecule (don’t remember second part of q)
any others? please lmk</p>

<p>Then it must be a trap. ISOLATED system is the keyword in this question. Heat should never change so the average KE reflecting temp shouldn’t change either.</p>

<p>F,Cl,N,O are highly electronegative but Cl DOES NOT form hydrogen bonds for some reason.</p>

<p>Also the more electronegative the compound / element connected to a H+ atom, more will be the acidic strength because of electron withdrawing that causes X-H bond to weaken.</p>