Radioactive Decay And Acid Dissociation Constant Chap. 9 And 10 Worksheet With Answers - Middle Tennessee State University Page 14
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20- 5
[6.93 x10
]
- 8
pK
= 4.16 - log
= 7.62
K
= 2.40 x10
a
a
b)
[0.200]
[0.000284]
- 7
c) pK
= 3.55 - log
= 6.27
K
= 5.37 x10
a
a
[0.150]
9.136 Bottles of ketchup are routinely left on the counters of cafes, yet the ketchup
does not spoil. Why not?
Solution
The vinegar in the ketchup makes the pH low enough (acidity high) that the
ketchup is like pickles (see Chemistry Around Us 9.2). The microorganisms
that makes many foods spoil cannot survive in the high acidity.
9.137 Refer to Figure 9.2 and answer the question. What implications does this
reaction have for the long-term durability of marble structures when exposed to
acid rain?
Solution
The CaCO
in the marble reacts with the acid to produce CO
gas. The acid
3
2
rain will react with marble, eroding the surface. Marble structures will
ultimately erode away under long-term exposure to acid rain.
9.138 Refer to Figure 9.3 and answer the question. Do you think the results would be
the same if sulfuric acid (H
SO
) were substituted for the HCl? Explain.
2
4
Solution
Yes. The most active metal reacts most vigorously. The reaction would be
the same using H
SO
, instead of HCI, for the three metals tested. If either
2
4
the chloride salt or the sulfate salt of the metal were insoluble, there would
then be a detectable difference in the reactions using HCI or H
SO
.
2
4
(See 9.1)
9.140 Refer to Figure 9.6 and explain why the pH reading of the meter might not be
7.00 at the equivalence point in a titration. Would the pH at the equivalence
point be greater or less than 7 if hydrochloric acid was titrated with aqueous
ammonia?
Solution
A titration of a strong acid with a strong base would have pH = 7.00 at the
equivalence point. If a weak acid is titrated with a strong base, hydrolysis of
-
the B
makes the pH greater than 7 at the equivalence point. If a weak base
(NH
) is titrated with a strong acid (HCI), the pH will be less than 7 at the
3
equivalence point.
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