May 2011 SAT CHEM

Test Preparation SAT Subject Test Preparation
141

<p>Abrayo, for the solution question you are referring to, I believe it was not saturated and the answer was II only.</p>

<p>If it were saturated, adding more KCL would not cause more precipitate (because it reached maximum solubility) however it formed more crystals; thus it was not saturated.</p>

<p>If you noticed that the reaction was endothermic, that means that stirring (in effect, increasing kinetic energy –> temperature) would, by LeChatliers Principle, cause a shift to the right, forming less solid, and more product.</p>

142

<p>@Stonesn: An isomer has the same chemical formula as the original. You just had to count up the C’s and H’s of all the answer choices and pick whichever one matched up to the original.</p>

143

<p>The isomer one was easy, wasn’t it? The other options didn’t even have the same number of Cs or Hs!</p>

144

<p>CSK is right…i put II only also…i dont remember the question but i remember it being fairly obvious</p>

145

<p>Isomer was 2-methylpentane, since that was the only one with 6 Carbons and 14 Hydrogens.</p>

<p>How the hell were you supposed to do the M3N question?</p>

146

<p>I didn’t get the M3N one… I left it for the end and didn’t have enough time to get back to it. I also seem to have gotten the KCl one wrong…</p>

147

<p>well you knew it was a 3:2 ratio in weight…and 3 Li’s was 21 grams to 14 grams of N thus a 3:2 ratio…also Li was the only element corresponding to the masses then fit the formula X3N is you didnt know any other way to do it</p>

148

<p>Volumetric flask is for preparing solution; pipet is for measuring.</p>

149

<p>After a few minutes of thought the M3N one was easy.
I multiplied by two to get M6N2, and since the molar mass of N2 is 28, and the given was 0.28, the answers would just be 100x more. So I subtracted to get .42 and then divided by 6 to get 0.07.</p>

<p>What KCl one?</p>

150

<p>If it were saturated, adding more KCL would not cause more precipitate (because it reached maximum solubility) however it formed more crystals; thus it was not saturated.</p>

<p>wrong
if it is saturated, no more particles would form, (be able to be hydrated by the water)
so it would percipitate
because it couldnt disolve anymore</p>

151

<p>@314159265
So the in the M3N question M and N occurred in the ratio .28g N to .42g M right? So .28 g N is .02 mol N, which would be .06 mol M. So then .42g M/ .06 mol M is about 7g/mol</p>

152

<p>For the KCl question, I don’t think LeChatelier’s Principle matters …
If you look at this solubility curve, it shows that decreasing temperature decreases the solubility of KCl: <a href=“http://www.saskschools.ca/curr_content/chem30_05/graphics/4_graphics/sol_curve.jpg[/url]”>http://www.saskschools.ca/curr_content/chem30_05/graphics/4_graphics/sol_curve.jpg&lt;/a&gt;&lt;/p&gt;

<p>Also, if the KCl is at equilibrium, then it has to be saturated</p>

153

<p>Does anyone even remember what the KCl question asked? I don’t, and I’m not sure what people are arguing about</p>

154

<p>what was the best oxidizng agent?</p>

155

<p>And for M3N, you didn’t even have to do calculations. Just look at the molar masses offered. The first one was 7 (Li), all of the other ones were of atoms that did not have a 1+ charge</p>

<p>ALSO - best oxidizing agent = the one that is most easily reduced</p>

156

<p>^exactly my point</p>

<p>Sowas it f2?</p>

157

<p>So the best oxidizing agent was F2, right?</p>

158

<p>On the M3N one I matched the molar masses up with the elements, and the only one that made sense was Li3N (MM = 7). You can also use ratios: 3*7/14 (nitrogen MM) = 42/28 (given).</p>

<p>The KCl one was I only. I had I and III at first, but took out III when I reread the choices. Since the reaction was endothermic, cooling it would add more KCl (s) to the solution, but choice III said something to the effect of, “Cooling the solution will release more KCl into the solution,” which I took to mean it would dissociate. By the way, there were both forward and reverse arrows on the equation.</p>

<p>On the lab tools questions, is the graduated cylinder used to measure liquids to precise volumes, or was that the pipet-looking thing? I had the pipet at first but changed it…</p>

159

<p>Pipet is more precise than a graduated cylinder. </p>

<p>aaand yes, F2</p>

160

<p>Was the T/F about the saltwater boiling point F/F?</p>