Chemistry BC2001x: Corrections to Weekly Problem Sets

I appreciate your telling me if you think you have found an error:
I would like to post corrections for everyone to see.

Solutions to practice problem set 11, page 2.  [posted 12/16/08]. Problem 3.c:

Δℰ° = Δℰ + (k_N/n) log Q = (1.755) + (0.05916/2) log (0.010) = 1.755 +(-0.05916) = 1.69584 V

Δℰ° = ℰ°_R - ℰ°_L, →  ℰ°_L = ℰ°_R - Δℰ° = 1.358 V - 1.69584 V = -0.338 V = ℰ°_{Tl+ | Tl}

and 3.e:   log K = n Δℰ°/ k_N = 2(1.69584) / 0.05916 = 57.33063 and K = 2.1 x 10⁵⁷

(this is a correction to a correction; my apologies.)

Solutions to practice problem set 10, page 7.  [posted 12/15/08].
Problem 6: value of K is wrong, it should be 4 x 10^-9

Solutions to practice problem set 11, page 3.  [posted 12/11/08].
Problem 4.b (no I^- in the cathode reaction):         PbO₂(s)+ 4 H⁺ + 2e^- ->  Pb²⁺ + 2 H₂O

Solutions to practice problem set 10, page 4.  Part i: there should be no coefficient of 2 with the H₂O in the net reaction. [posted 12/10/08].

Solutions to practice problem set 10, page 6.  Part 2: remove two waters from the products of the oxidation, put them in the net reaction. [posted 12/10/08].

Solutions to practice problem set 12, page 4.  Part a: the numerator in ln K
was supposed to be converted to kJ (multiplied by 1000): [posted 12/5/08].

1n K = -ΔG°/RT = -(-503,830 J/mole) /{(8.314472 J/K-mole)(298.15 K)} = 203.24250
K = e^203.242 = 1.84968 x 10⁸⁸ = 1.8 x 10⁸⁸

or  1og K = -ΔG°/(2.303RT) = -(-503.83 kJ/mole) / (5.70804 kJ/mole) = 88.2669
K = 10^88.2669 = 1.85 x 10⁸⁸

Solutions to practice problem set 10, page 4.  Part f: there should be no coefficient of 8 with the Al(OH)₄^- in the half-reaction. [posted 12/5/08].

Solutions to practice problem set 5, #8. Significant figure error: the molarity should be 5.55 (both the percent by weight and the density had only 3 sig. figs.) Subsequent values were calculated with unrounded previous numbers, even though I show only one or two extra. [posted 10/16/08].

Solutions to hand-in problem set 3B part a: water should have coefficient 2 in the balanced equation, as explained in the text.  It is correct on the second page.  (corrected version posted on Courseworks.) [posted 9/25/08]

Solutions to practice problem set 3, page 8 (problem 12.5.v: HCO₃^-):
Some of the lone pairs have not shown up.  In particular, the O attached to the H is missing electrons in all three structures. Corrected page here. [posted 9/25/08]

Solutions to hand-in problem set 2D, part c (attached to problem for those doing version D).  I said that none of the percentages match, while in fact two do not, but one (oxygen) is ok.  Change it to read (change in red):
Neither the C nor the H calculated values agrees with the experimentally determined value to within the estimated experimental uncertainty, although...  [posted 9/22/08]