June 2009 - Chemistry

<p>wikipedia confirms that NaF has the highest boiling point (darn i missed it)
What was the exact question for 101? I slightly remember it but not specifically.</p>

<p>According to this [melting</a> points Text - Physics Forums Library](<a href=“Understanding Melting Points for the Periodic Table”>Understanding Melting Points for the Periodic Table) the melting points decrease going down the halogen group, making NaF the largest MP.</p>

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<p>Thought it said which CAN be collected? HCl being “uncollectable” is correct though.</p>

<p>the melting point of NaF is 993 degrees celsius compared to 801 degrees celsius for NaCl therefore the higher the electronegativity difference the stronger the bond, and thus the melting point is higher. since At is below cl the melting point would be even lower.</p>

<p>volume decresed pressure increases cuz of something i put TTCE
wat u put?</p>

<p>hm i just want 770+</p>

<p>You’re right- I apologize! NaF has the highest melting point.</p>

<p>wat about my question lol?</p>

<p>101 as definitely not TTCE. It said constant temperature so speed doesn’t increase as volume decreases.
[Kinetic</a> Molecular Theory](<a href=“http://www.mikeblaber.org/oldwine/chm1045/notes/Gases/Kinetic/Gases08.htm]Kinetic”>http://www.mikeblaber.org/oldwine/chm1045/notes/Gases/Kinetic/Gases08.htm)</p>

<p>Search “Effect of volume”</p>

<p>Should be T/F</p>

<p>So, this is really basic, but the one about Fe2(NO3)3 dissociates into 5 ions right? I couldn’t think straight. </p>

<p>And yeah, I vote NaF.</p>

<p>I think i got a raw score of 76-77/85
is a 770-790 possible?</p>

<p>yea i put 5 moles of ions for that one</p>

<p>but most of the ionic compounds exist in the so-called ‘network’ structure in which the attraction forces between the negative and positive ions join them together (you guys can look up the structure of NaCl, NaF,…in your textbooks).
So when you heat the compound, you are in fact breaking these forces of attraction between ions, which means you are actually breaking the bond between Na+ and F- itself…
this also explains why ionic compounds can only conduct electricity when molten (because ions are free to move in the molten state)
therefore NaF should be the correct answer :)</p>

<p>yes 5 10 Char</p>

<p>^ Was that the one where it said V decreases, P goes up because at lower V the gas molecules are moving faster? First part is true by Boyles law, second is false (avg velocity dependent on T only assuming we’re dealing with the same gas).</p>

<p>Anyone want to guess the curve? I think this was an average test so maybe 80/85 = 800?</p>

<p>and there was also NA+ and so4 as an answer dont remembr which question</p>

<p>somebody confirm number 101 and number the H2S HCl question
i put TTCE and 1 as the coiffencent</p>

<p>So far 5 wrong, 1 omit. Hoping for a 750 +. Though, looking at this thread, I’m pretty sure I got almost everything else right. Except the TTCE questions; I didn’t have a chance to recheck them. </p>

<p>Burette and flask (in the first set of questions) was not used, right?<br>
Sulphur and Iron filings = magnetic
NaCl and h20 = distillation
NaNo3 and precipitate = filter paper and funnel
I forget the other one.</p>

<p>what was the one with water boiling at a lower temperature at higher altitudes?</p>

<p>expect 79/85 for 800 </p>

<p>anybody remember the covalent bon question</p>

<p>It was</p>

<p>Water has a lower boiling point at high altitudes (true)</p>

<p>because</p>

<p>At higher altitudes atmospheric pressure is higher (false)</p>

<p>I think the boiling pt was T F</p>

<p>Higher altitude = lower BP
Higher altitude =/= higher atmospheric pressure</p>

<p>no it was on pressure temperture and volume of an ideal gass</p>