<p>Anyone have tips on solving log stuff on the multiple choice?</p>
<p>^ well for MC I’m thinking it wont get to math intensive, so I would estimate. Let’s say the [H+] is like 3.34 <em>10^-4 and they are asking for a general idea of the pH. pH=-log[H+] which in this case (using a calc) is 3.47. WITHOUT A CALC: I look at the exponent on 3.3</em>10^-4 and that tells me that the PH is between 3 & 4 (I took the opposite sign of the exponent 4, and the number below that, 3). There are ways to be more specific but that will give you the general idea for MC.</p>
<p>Ok, I have been taking practice multiple choice exams, and i have been consistently scoring 37-45 mc correct every time. One question that I always get incorrect are quantum numbers. I have been looking for explanations and have not found one that makes sense to me. Do I just have to memorize the stiff or is there some way to know it. Please give me an explanation, and here is a question from the test: “13. This is the last electron added in the element with the lowest ionization energy.”
A. 1,0,0, (1/2)
B. 3,4,3, (-1/2)
C. 3,2,0, (1,2)
D. 5,0,0, (1/2)
E. 2,0,0, (-1/2)</p>
<p>please help me out with this stuff. I know lowest ionization energy is farthest away from noble gases, its just the quantum numbers which screw me up</p>
<p>How stringent will they be on the rounding for the free response? For some reason I keep missing the answers by one unit on last year’s problems. They show .328/10.5 = .0313 for example and I get .0312. Same thing with some of the other parts.</p>
<p>Oh yeah, also i need help on doing this math without a calculator. For example, how would you do this .012 divided by 183 (.012/183)? any help would be appreciated</p>
<p>So, we’re only a step away from taking the exam.
What are you guys doing for review these couple of days? Do you advice on last-minute study? Some people think that nothing can be changed if only 2 days are left.</p>
<p>Also, what is the point of looking at the old exams if those questions are NOT going to be on this year’s exam? </p>
<p>So as you can tell, I am freaking out! 2 days leftttttt!!!</p>
<p>A. 1,0,0, (1/2)
B. 3,4,3, (-1/2)
C. 3,2,0, (1,2)
D. 5,0,0, (1/2)
E. 2,0,0, (-1/2)</p>
<p>Is the answer D?</p>
<p>If so, it’s because the 5 indicates that the element is in the fifth row down. Going down the periodic table makes it easier to take away an electron from the outermost shell (that’s what ionization energy is). </p>
<p>The 0 just means that it’s in the s orbital, which is the first two columns of the periodic table.
1 correlates to the p subshell, 2 would correlate to the d subshell, etc.</p>
<p>Fearmaster,</p>
<p>I would make it 1200/180 and reduce to 20/3, which is 6 2/3 or 6.67. Then move your decimal point five places (undoing 0.012 -> 1200). Pick the closest answer.</p>
<p>But I don’t think the math would be that hard on the MC section. Maybe you’re solving the problem the wrong way?</p>
<p>^^Im pretty sure your answer was correct, but the test im taking will not let me go back to see. Thank you for your explanation, but what about the two middle numbers, in this case 0,0</p>
<p>@Daisie, thank you, i probably was solving the problem in the wrong way. I just see all those numbers and a huge paragraph, and my mind wants a calculator and to do the math in a hard way to solve it. Thank you very much. and can someone explain to me how to do empirical formula problems quickly and efficiently on the multiple choice. I see myself being bogged down by all the math and losing precious time and maybe missing some easy questions in the process.</p>
<p>^ [Quantum</a> number - Wikipedia, the free encyclopedia](<a href=“http://en.wikipedia.org/wiki/Quantum_number]Quantum”>Quantum number - Wikipedia)</p>
<p>Scroll down to the table.</p>
<p>Daisie that is such an easier table to look at, thank you so much, my teacher was explaining it in such a complicated fashion, that was so much easier.</p>
<p>My teacher was talking about CollegeBoard puts hints in the problems to give you the vant Hoff factor in freezing point depression/boiling point elevation problems. He said they say, “nonionizing, molecular, or volatile,” to say the vant Hoff is 1. Did he make a mistake?</p>
<p>Volatile means low IMF, which means it is polar and WILL dissociate. Did he screw up?</p>
<p>can anybody explain 3rd and 4th quantum number for me? I googled it numberous times but it still does’nt make much sence to me.</p>
<p>For l=0 (which is s) the only possible m sub s is 0 right? and for p block is can be either -1, 0 or +1, am I right?</p>
<p>Volatile means that the compound is likely to vaporize, so yes, that would mean the compound would have low IMFs. However, I am not sure if that would mean it is polar or if it will dissociate.</p>
<p>@Kamenskih: 3rd quantum number is any value from -l to l (l being the 2nd quantum number). 4th number is the “spin”… so the up and down arrows in orbital diagrams. +1/2 is the up arrow, -1/2 is the down arrow.</p>
<p>Yes, you are right.</p>
<p>Can anyone tell me to what extent we need to know organic chemistry? We have never covered this in class, so i have no clue.</p>
<p>@AbrayoI think the answer is I, II, and III.</p>
<p>Third:
The strength of acids formed in water is based on which of the following?</p>
<p>I. The polarity of the molecule - On the website below, it says the greater the polarity the stronger the acid.
[Factors</a> that Affect the Relative Strengths of Acids and Bases](<a href=“http://library.thinkquest.org/C006669/data/Chem/acidsbases/factors.html]Factors”>http://library.thinkquest.org/C006669/data/Chem/acidsbases/factors.html)</p>
<p>II. The size of the molecule- (This is true because the bigger the molecule the more likely it is the pick up electrons. Remember that Acid is not only a proton donor but also an electron pair acceptor.Small ions are more unstable.)</p>
<p>III. The strength of the bond- weak bonds make the H+ ion more readily available in the solution</p>
<p>how many mc questions right do you guys think is on track for a 5 this year with the no guessing penalty. like 55 or 60?</p>
<p>fatal1030: Polarity should not be tightly associated with strengths of acids/bases because of the many caveats. HF has a huge dipole moment, but is not a strong acid. It has a higher polarity than HCl, HBr, HI, etc in fact.</p>
<p>What do you guys think of this? Is this just one of those few exceptions that stray from the general trend or what?</p>
<p>Could someone help me with these questions?</p>
<ol>
<li><p>Which of the following would produce the LEAST mass of CO2 if completely burned in excess oxygen gas? (I know how to do this, but it takes too much time).
(A) 10.0g CH4
(B) 10.0g CH3OH
(C) 10.0g C2H4
(D) 10.0g C2H6
(E) 10.0g C4H5OH</p></li>
<li><p>In an aqueous solution with a pH of 11.50 at 25 degrees C, the molar concentration of OH-(aq) is approximately (I know how to do this with calculator, but without one, I’m stuck between B and C.)
(A) 3.2 * 10^-12 M
(B) 3.2 * 10^-3 M
(C) 2.5 * 10^-1 M
(D) 2.5 M
(E) 3.2 * 10^11 M</p></li>
<li><p>Which of the following aqueous solutions has the highest BP at 1.0 atm?
(A) 0.20M CaCl2
(B) 0.25M Na2SO4
(C) 0.30M NaCl
(D) 0.30M KBr
(E) 0.40M C612O6</p></li>
<li><p>Of the following, which reacts violently with water 298K? (Is it Rb because it’s an alkali metal?)
(A) Au
(B) Ag
(C) Cu
(D) Mg
(E) Rb</p></li>
<li><p>A steady electric current is passed through molten MgCl2 for exactly 1.00 hour, producing 243g of Mg metal. If the same current is passed through molten AlCl3 for 1.00 hour, the mass of Al produced is closest to
(A) 27.0g
(B) 54.0g
(C) 120.g
(D) 180.g
(E) 270.g</p></li>
</ol>
<p>Also, adding heat to a system at equilibrium is different from changing the temperature, right?</p>
<p>@ Skateme: </p>
<p>Thats a really good point. Fluorine (F) is the most electronegative element. Because of this, F has a very strong hold on to H+ as compared to the strong acids (ex. HCl). Because of this, the H+ in HF is not readily available to the solution. This means that HF is an exception to the general polarity rules regarding acids. The answer the question i posted earlier is II and III. Perhaps, this exception makes choice “I” wrong. But i am not sure.</p>