CHEMISTRY 31

Summer, 2016 - Dixon

Homework Set 1 (for Exam 1)

Note:  Text problems will not be collected but there will be a 10 point quiz on the homework completion date unless otherwise specified

Chapter Problems Date to finish    

Set 1.1                                                                                                          June 2

Ch. 1                                              1a, 5, 11, 15, 20, 23, 26, 32, 35

Turn in corrected diagnostic quiz by Feb. 4 June 2 (10 points).  No Homework to Turn in

Set 1.2                                                                                                          June 9

Ch. 1                                              37, 42, 46

Ch. 3                                              1, 2, 5a-d, 11, 14, 16a-f

Ch. 4                                              4a, b, 9, 11

Additional Problem 1.1 (3 points)

The following method is used to capture, oxidize and titrate sulfur dioxide (SO₂) in air in order to measure its concentration.  Air is bubbled into 25.0 mL of an 0.0050 M NaOH solution at a rate of 1.00 L (air)/min for 151 min.  Excess hydrogen peroxide is present which converts the sulfur dioxide into sulfuric acid through the following reaction:

                        SO₂(g) + H₂O₂(aq) ↔ H₂SO₄(aq) + H₂O(l)

The sulfuric acid is neutralized by the OH^-.  The excess NaOH (that not reacted with H₂SO₄), then is titrated with HCl, and required 38.1 mL of 0.00233 M HCl.  Determine the concentration of SO₂ in the air in nmol/L.

Additional Problem 1.2  (4 points)

A chemist wishes to weigh out iron for a reaction but her balance is broken.  She decides that she can determine the mass of iron by measuring the length and diameter of an iron rod.  The density of iron is 7.86 + 0.01 g cm^-3, the length of the rod is 32.4 + 0.4 mm and the diameter of the rod is 4.16 + 0.05 mm.

a) Calculate the mass of iron added. The volume of a rod equals π·d²·l/4, where d is the rod diameter and l is the rod length.

b) Calculate the uncertainty in the mass of iron added.

c) Which measurement contributed most to the overall uncertainty?

solutions to additional problems 1.1 and 1.2

Set 1.3                                                                                                          June 16

Ch. 4                                              20, 21, 30

Ch. 6                                              4, 6

Additional Problem 1.3  (3 points)

3.  A certain 100 point quantitative analysis exam has an average value of 64.2 and a standard deviation of 19.0.  If the cut-off limit for an "A" is 87, determine what percentage of students should be getting an A.  Assume the distribution of test scores is Gaussian, and use the Z-Table below - find the closest Z value; do not interpolate.

solutions to additional problem 1.3