59-320 Homework Assignment - Chapter 1
59-320 Homework - Chapter 1
Note: For Exercises, complete solutions are given at the back of the book, and
for Problems, only numerical answers are provided. The Exercises are the most
important to do, since they cover most of the major ideas. The Problems are
very short, usually hitting upon one concept at a time.
On differences between the 7th and 8th edition:
Since discussions of titrations (Sections 7-1 and 7-2, 7th edition) have been
moved into this chapter (Section 1-5, 1-6), there are some changes in the
overall layout and numbering of questions. If questions have no special
markings, they are the same numbers in both editions. Students with 7th edition
should also read Section 7-1 and 7-2 in studying the first section of this course.
Major differences:
• 1-D and 1-E below are from a different chapter in the 7th edition.
Exercises
1-A. A solution with a final volume of 500.0 mL was prepared by dissolving 25.00 mL of
methanol (CH3OH, density = 0.791 4 g/mL) in chloroform.
(a) Calculate the molarity of methanol in the solution.
(b) The solution has a density of 1.454 g/mL. Find the molality of methanol.
1-B. A 48.0 wt% solution of HBr in water has a density of 1.50 g/mL.
(a) Find the formal concentration of HBr.
(b) What mass of solution contains 36.0 g of HBr?
(c) What volume of solution contains 233 mmol of HBr?
(d) How much solution is required to prepare 0.250 L of 0.160 M HBr?
1-C. A solution contains 12.6 ppm of dissolved Ca(NO3)2 (which dissociates into Ca2+ +
2NO3-). Find the concentration of NO3- in parts per million.
1-D (7-A, 7th ed.). Ascorbic acid (vitamin C) reacts with according to the equation
C6H8O6 + I3- + H2O → C6H8O7 + 3I- + 2H+
ascorbic acid
dehydroascorbic acid
Starch is used as an indicator in the reaction. The end point is marked by the
appearance of a deep blue starch-iodine complex when the first fraction of a drop of
unreacted I3- remains in the solution.
(a) Use atomic masses from the periodic table to find the formula mass of ascorbic acid.
(b) If 29.41 mL of I3- solution are required to react with 0.197 0 g of pure ascorbic acid,
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59-320 Homework Assignment - Chapter 1
what is the molarity of the I3- solution?
(c) A vitamin C tablet containing ascorbic acid plus inert binder was ground to a powder,
and 0.424 2 g was titrated by 31.63 mL of I3-. Find the weight percent of ascorbic acid in
the tablet.
1-E (7-B, 7th ed.). A solution of NaOH was standardized by titration of a known quantity
of the primary standard, potassium hydrogen phthalate:
C8H5O4K + NaOH → C8H4O4NaK + H2O
potassium hydrogen phthalate (MW = 204.221)
The NaOH was then used to find the concentration of an unknown solution of H2SO4:
H2SO4 + 2NaOH → Na2SO4 + 2H2O
(a) Titration of 0.824 g of potassium hydrogen phthalate required 38.314 g of NaOH
solution to reach the end point detected by phenolphthalein indicator. Find the
concentration of NaOH (mol NaOH/kg solution).
(b) A 10.00-mL aliquot of H2SO4 solution required 57.911 g of NaOH solution to reach
the phenolphthalein end point. Find the molarity of H2SO4.
Problems
Units and conversions
Optional: very easy unit conversions
1-1, 1-2, 1-3, 1-4
Do these for sure
1-5, 1-10
Chemical Concentrations
Easy:
1-12, 1-13, 1-14, 1-17
Others:
1-18, 1-19, 1-20
Challenging:
1-22, 1-26
Preparing solutions
1-28, 1-29, 1-32
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59-320 Homework Assignment - Chapter 1
Stoichiometry
1-34, 1-35
Titrations
Easy qualitative study points:
8th: 1-36, 1-37, 1-38, 1-39, 1-40, 1-41
7th: 7-1, 7-2, 7-3, 7-4, 7-5, 7-6
Titration calculations:
8th: 1-43, 1-46
7th: 7-7, 7-11
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