Errors in Ch 20 - sample and practice exercises, Go Figure, Self-Assessment, etc.

[Zellmer, Robert]

The following also has corrections for sample exercises, Go Figure questions and
Self-Assessment exercises.  Some are simple formatting errors in the text.  Some
are errors in sig. fig.

Section 20.2:

Practice Exercise 20.2:

Two mistakes.  The coeff of H^+ is wrong and the H2O on the right is cut off.
Cu(s) + 4 H+(aq) + 2 NO3^- (aq) ⟶ Cu^2+(aq) + 2 NO2(g) + 2 H2O(l)

It appears that if you’re using an iPad and you turn it to Landscape mode the reaction
eqn doesn’t get cut off.


Practice Exercise 20.3:

Two mistakes.  Can’t see the whole reaction eqn. in the answer.  There’s a 2 OH^-(aq)
on the product side which was cut off. The H2O is liquid whereas the answer as a
capital “L” for the state symbol.

It appears that if you’re using an iPad and you turn it to Landscape mode the reaction
eqn doesn’t get cut off.


Section 20.5:

Sample Exercise 20.10:

The solution to this exercise does not deal correctly with the sig. fig..  If you carry
extra digits from one step to the next all the way through you wind up with K = 1.2 x 10^29
(the book has 9 x 10^29).

Practice Exercise 20.10:

No temp given.  They assume 25 C.  If a temp isn’t given, we normally assume 25 C.

Self Assessment Ex. 20.14:

The correct answer is (c) -1.3 x 10^2 kJ/mol.  The answer given in the box is (c) but they
have -67 kJ for delta(G).  Also, no temp was given in the question so assume 25 C.


Section 20.6:

Sample Exercise 20.11:

State symbol for H2O in balanced eqn is a capital "i".  It should be a lower-case “L”.

Sample Exercise 20.12:

Sig. fig. error.  If you carry extra digits throughout the problem you get a pH = 5.24 and
it should have two decimal places (since for pH the s.f. are to the right of the decimal place).

Practice Exercise 20.12:

I get a slightly different answer than the book.  I get pH = 4.18.  It’s probably another sig. fig.
error.  Note, they state E^o to three sig. fig. but have only two decimal places for pH.  That
means they’re counting the “4” in the units place as a s.f. and that’s incorrect.

Sample Exercise 20.13:

Sig. fig. error. again.  However, the pH I get (pH = 3.56) is essentially the same as the
book’s value of 3.57.

Practice Exercise 20.13:

There’s no answer for question (b).  It should be E = 0.105 V.


Section 20.7:

Go Figure 20.19:

Typo.  They have PbO^2 instead of PbO_2 in the answer.


Section 20.9:

Paragraph after Go Figure 20.29 has E_Ted for the water oxidation reaction in the
equation.  It should be E_red.  In the paragraphs below that there’s a couple of
instances of E_req which should be E_red.

Self-Assessment 20.27:

I’m getting 41 min and the answer given is 42 min.  Probably they rounded at
some point before the final answer.


Dr. Zellmer
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