<p>Diana, that question was EXACTLY like a question on our final exam... which was a special teacher's only exam from the collegeboard. How'd you find it?</p>
<p>Answer to previous - [Ag(NH3)2]^+1</p>
<p>All of these molecular shapes can be explained by dsp3 hybridization of electrons on the central atom EXCEPT
A. Linear
B. T-shape
C. See-saw
D. Octahedral
E. Trigonal bipyramidal</p>
<p>^ </p>
<p>Its D. Octahedral, because there are 6 atoms attached to the central atom in an octahedral, and sp3d is only 5.</p>
<p>Next question: What is the final concentration of lead ions, [Pb2+], in solution when 100 ml of 0.10 M PbCl2 (aq) is mixed with 100 ml of 0.050 M H2SO4 (aq)?</p>
<p>.050 M Pb2+ ( (.100 L x .10 M) / .200 L total )</p>
<p>at what conditions do gases behave most ideally?</p>
<p>High temperature, low pressure.</p>
<p>I. HCl/KCl
II. NH4Cl, NH3
III. HF/NaF</p>
<p>Which would not form a buffer system?
A) I
B) II
C) III
D) I and III
E) I, II, and III</p>
<p>High temperature and low pressure</p>
<p>erm.. can we go back to</p>
<p>Which description applies to the reaction below?</p>
<p>AlCl<em>3 + Cl^- ---> AlCl</em>4</p>
<p>A. amphotorism
B. anion hydrolysis
C. Arrhenius neutralization
D. Lewis acid-base reaction
E. Bronsted-Lowery proton transfer</p>
<p>and someone explain it...</p>
<p>D. Lewis acid-base reaction</p>
<p>Cl- acts as the base, and AlCl3 acts as the acid. Definition of Lewis acid-base reaction is that the base donates a pair of electrons (Cl-) and an acid can receive pair of electrons (AlCl3, if you draw the geometry and Lewis dot structure you can see there is an available spot on Al for an electron pair to go)</p>
<p>It is not A. because that means a substance can act as a base or acid
It is not B. because nothing is hydrolized
It is not C. because Arrhenius definiton involves accepting/donating H+
It is not E. because no protons are transfered</p>
<p>Someone correct me if I am wrong.</p>
<p>Next question (free response new reaction format)</p>
<p>Carbon disulfide vapor is burned in excess oxygen.</p>
<p>Write the equation (BALANCED) and answer this question:</p>
<p>What is the oxidizing agent in this reaction?</p>
<p>Another practice problem for new reaction format.</p>
<p>Solutions of sodium hydroxide and acetic acid are mixed. Give the balanced reaction. Also, acetic acid is considered weak, so if equal amounts of equal molar solutions are mixed, what will the solution's pH be,
A. 14
B. 7.1-13.9
C. 7
D. 1.1-6.9
E. 1</p>
<p>ANSWER to previous reaction:</p>
<p>CS2 + 3O2 ---> CO2 + 2SO2</p>
<p>O2 is the oxidizing agent because O goes from oxidation number of 0 to -2 (thus, reduced, and so is the oxidizing agent)</p>
<p>
[quote]
.050 M Pb2+ ( (.100 L x .10 M) / .200 L total )</p>
<p>at what conditions do gases behave most ideally?
[/quote]
- Adelaide</p>
<p>Can you explain how you got to that answer for the molarity problem?</p>
<p>Equilibrium, sorry for such a postponed reply (because of the time gap)
well we took it as a final as well
but i just brought my exam paper back and took a look at it,
trying some of the tricy questions once again....:D</p>
<p>Sunil7desi,</p>
<p>What is the final concentration of lead ions, [Pb2+], in solution when 100 ml of 0.10 M PbCl2 (aq) is mixed with 100 ml of 0.050 M H2SO4 (aq)?</p>
<p>I think this question can be interpreted in two different ways
First, if the question is asking after REACTION btw the two, we solve like the following:</p>
<ol>
<li>write the formula: pbcl2 + H2SO4 -> PbSO4 + H2CL2.</li>
<li>100ml of 0.1M means that there are 100*0.1 = 10 mmoles of Pbcl2.
100ml of 0.05M means that there are 0.05 * 100= 5mmoles of H2SO4.</li>
</ol>
<p>pbcl2 + H2SO4 -> PbSO4 + H2CL2
10 5</p>
<h2>5 5</h2>
<p>5 0 -> The limiting reagent is H2SO4, so only 5 mmoles are used in the reaction.</p>
<p>which means that there will be 5 mmoles of PbSO4 in the product.
5mmole = 0.005 mole
we MIXED 100ml+100ml so the total volume is 200ml = 0.2L
Therefore
Molarity = N/V = 0.005/0.2 = 0.025M</p>
<p>The answer will be 0.025 M</p>
<p>BUT!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
before you check your answer (like what i did)
you have to add 5mmoles which REMAINED at the beginning b/c pbcl2 was in excess. Thanks to Audiorage18, the answer has to be 0.01/0.2 = 0.050M.</p>
<h2>My bad :D</h2>
<p>But i think Adelaide solved it under assumption that the two are just being MIXED(which the question is obviously saying)</p>
<p>if we solve like what Adelaide did,
.050 M Pb2+ ( (.100 L x .10 M) / .200 L total )</p>
<p>the first pb2+ is there b/c it is the initial amount of pb2+ in the mixture
(b/c it's not the REACTION, it remains the same)
and the ones in the parenthesis are the molarity of the newly put pb2+. 0.100L * 0.10M is the number of moles and 0.200L total is 100ml+100ml.</p>
<p>The reason why im confused w/ these two solution is bc
the <em>usual</em> questions i've seen were like the first solution..
maybe this is easier type of question..:D</p>
<p>Hmmm, in regards to the Pb question, I got an answer of 0.050 M, so any clarification would be awesome.</p>
<p>I did it like Diana Oh's first part, but I think she forgot to add the excess Pb from the beginning. 5 millimoles of Pb from the products but also 5 millimoles left from reactants, no?</p>
<p>oops my bad audiorage 18.. it definately has to be added...
0.01/0.2 = 0.050M MY BAD!!!!!!!!!!</p>
<p>yeah i just read through all that. very interesting and good job to everyone</p>
<p>can someone explain lattice energy?</p>
<p>Oh wow, that is really tricky question. I mean now it was a really dumb mistake on my part, they are asking for TOTAL conc. of ions in SOLUTION, which includes basically everything, right?</p>
<p>I got it, good job guys.</p>
<p>anybody have any specific tips for MC part of the test?</p>
<p>i would like to know tips
back to what i was previously asking
does anyone know tricks like
LEO the lion goes GER
or RICE or anything of the sort?</p>
<p>ya i know one. OILRIG (oxidation is losing, Reducing is gaining (assuming you understand the reference to electrons)).</p>
<p>For the [Pb+2] problem..</p>
<p>I think you need to know the Ksp of PbSO4 because that does not fully dissolve in water. PbCl2 and H2SO4 is normally 100% spontaneous reaction. Its usually a precipitate reaction. Therefore there is no lead ions in the solution, only HCl solution with lead sulfate solid (yellow).</p>