<p>did everyone get a positive number for number 2, part E?</p>
<p>NoxLuminus, I got 4.08 using H-H equation and letting the base be the F- calculated in the previous part and letting H3O concentration be what was calculated earlier.</p>
<p>darkruler is right about MnO4 though.</p>
<p>yeah, it should be positive.</p>
<p>starburst, do you mean +354.46 kJ or something like that? I forget the sign, but the number is right.</p>
<p>To do the last question on Q1, you either use Henderson-Hasselbalch or use the Equilibrium expression and subtract x from [HF] and add x to both [H+] and [F-] and then use the estimate where [H+ +x] = [H+].</p>
<p>For the part e question 1</p>
<p>pH = -log(Ka) + log (base/acid)</p>
<p>pH = -log(7.2 x 10-4) + log(.15/.25) = 2.92</p>
<p>was the number of moles of H3O+ in the solution .004
and was the [F-] = .15M since there were .006 mol/.040L?</p>
<p>dark ruler for the concentration of the acid you have to take the original concentration of acid HF, which is equal to .025 x .40 = .01 / .04 = .25</p>
<p>it was weak acid titrated by base, i got 3.32 first but that was way too low for HF but once you factor out the remaining [OH] the pH is 9.69</p>
<p>I don' thing that is right Ptang.</p>
<p>Yeah, usually on those problems the base and acid are already known from other parts.</p>
<p>Edit: well I dont wanna start worrying about it like I did for E and M, so have fun...</p>
<p>Also, igestmoney, it isn't above 7 because you have not reached the equivalence point yet. you added less NaOH than HF, so it would still be acidic.</p>
<p>Heres my answers for the 1st 3 questions</p>
<p>1
b. 0.17 M
c. 0.004 moles
d. 0.15 M
e. pH = 3.319</p>
<p>2.
a. -181.156 kJ
b. Meh, I messed this up like eveyrone else
c. -33.792 kJ
d. 6 bonds
e. 140.667 kJ</p>
<p>3
d. 343.487 kJ
e. 1.186 g
f. 0.197 L O2</p>
<p>Right?</p>
<p>And the reaction equation question 1 was 1/2 moles of product wasnt it? I put 0 because I was thinking only whole numbers....dumb dumb dumb.</p>
<p>hells yeah, thanks for posting that mike. it makes me feel like I got what someone else got. I think its right. makes me feel good!</p>
<p>yeah, i screwed up b tho too.</p>
<p>how do u do it then cuz I no darkruler is wrong</p>
<p>what was color change for 5 was it purple to pink?</p>
<p>what was 2 B the question i dont remember?</p>
<p>^^^ Thats what I had. Except for part of one, but I know I did it wrong, so I agree on most everything :).</p>
<p>darkrulerII is correct "I did -log(PKa) + log(.15/.1)" pH = 3.31</p>
<p>for Question 2 (b), the temp is not 298. Whoever said set dG to zero is correct.</p>
<p>Question 5 (lab question) my answers</p>
<p>a.) oxidation number of Mn in MnO4- is +7
b.) reducing agent is Fe2+
c.) clear -> purple
d.) i.) 5MV ii) 5(55.85)MV iii)5(55.85)MV/g
e.) you overestimate % of iron cuz u overestimate amount of iron in the sample</p>
<p>ok, yeah, thats what I got for Q5, except I forgot to put the 5 in part D. Do you think they will just take 1 point off, or take the point off in each part?</p>