FV 6-26-13
EXPERIMENT 1C:
ZINC THE BISMARCK
MATERIALS: Ruler, thirty-three galvanized washers, one red washer, 3 M hydrochloric acid, three 50 mL beakers,
150 mL beaker with graduations.
PURPOSE:
In this experiment, the student will determine how many millimeters of zinc, and layers of zinc
atoms, are present on a galvanized steel washer. The volume and density of the washer will be determined by
graphical means using MS Excel. This lab introduces the student to the nature of physical measurements and the
importance of accuracy, precision, significant figures, and proper units.
LEARNING OBJECTIVES:
1. Understand the relationship between experimental measurements, precision and significant figures.
2. Apply the rules for significant figures.
3. Create tables/graphs in Excel and use them to determine properties not directly measured.
4. Describe the differences in the precision of the analytical and top-loading balance.
5. Calculate percent error.
6. Use dimensional analysis for problem solving.
DISCUSSION: Corrosion can result when materials interact with their environment. Whether caused by a
salt-water environment, contact between dissimilar metals, or stray electrical currents, corrosion can lead to device
failure. One way to protect materials (i.e. steel washers) from corrosion is to “galvanize” them. During this
process, the base material is coated with a thin layer of a more reactive metal (i.e. zinc). Because zinc is more
reactive than iron, it protects the load-bearing material by sacrificially corroding. In the Navy, we similarly protect
our steel ships from rusting by attaching zinc plates to the iron hull. In one example
(http://www.kbismarck.com/wreck.html) no sign of the zinc plates remains on the hull of the sunken ship Bismarck
after decades of corrosion!
PROCEDURE: (**Work in pairs for Part B.
Caution:
Parts A and C will be done individually.**)
No flames are permitted in the laboratory during this experiment.
Part A:
1. Obtain a galvanized washer. Measure every dimension of the washer and record in the Data Section.
Have your instructor check your data before proceeding.
2. Use the analytical balance to measure the mass of the washer and record in the Data Section.
3. Obtain 10 mL of 3M hydrochloric acid in a 50 mL beaker. Working in the fume hood, place the washer in
the acid and let it react until the vigorous effervescence stops. Using forceps, carefully remove the washer,
rinse with distilled water, and dry thoroughly.
4. Use the analytical balance to measure the mass of the dry washer and record in the Data Section.
5. Dispose of the reaction mixture down the drain. Dispose of the washer in the beaker labeled “waste
washers”.
6. In the Data Section record the dimensions and mass of a different washer measured by another student.
Compare the values for each washer.
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Part B:
1. Place 70-80 mL of water in a 150 mL beaker. Record the actual volume, to the nearest 1 mL, as read from
the graduations on the beaker. Weigh the beaker filled with water on a top-loading balance. Record all
data in the Data Section.
2. GENTLY place 5 unreacted washers into the beaker. Record the new mass and volume in the Data Section.
3. Repeat step 2, recording total mass and volume readings, until 30 washers have been added to the beaker.
Do not let water splash out, and ensure the washers are completely underwater. When complete, decant
(pour off) the water and dry the washers thoroughly.
Part C:
1. Measure the outside diameter of the designated RED WASHER and record in the Data Section. Also record
the diameter in your instructor's class summary table. Keep the RED WASHER in its designated location.
DATA SECTION
Part A:
Record the dimensions and mass of your washer in the table below. Have your instructor check your
data before putting your washer into the 3 M HCl. Use the correct number of significant figures for each
instrument.
Outside diameter
(mm)
Hole diameter
(mm)
Thickness (mm) Original mass (g) Mass after reaction (g)
Washer 1
Washer 2
Part B:
Instructor Initials: ________
Record the number of washers immersed, mass and volume data in the table below. Use the correct
number of significant figures for each instrument.
# Washers
Part C:
Mass (g)
Record the outside diameter of the RED WASHER.
Volume (mL)
Include your data in the instructor's summary table.
Outside diameter (mm) of RED WASHER _________
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DATA TREATMENT
Part A:
1. For your washer, calculate the following (show all work). Record the values for both washers in the table below.
(Hint: Area of a circle = πr2, Circumference of a circle = 2πr)
(a)
the total surface area (mm2)
(b)
the volume of the zinc coating (mm3) (Hint: Use density of zinc from Pre-Lab)
(c)
the thickness of the zinc coating (mm)
(d) the thickness of the zinc coating in layers of atoms -assume the zinc atoms are arranged one on top of
the other as shown below. (Hint: Use Zinc atomic radius from Pre-Lab)
Surface Area
(mm2)
Volume
(mm3)
Thickness of Zn
coating (mm)
Thickness of Zn coating
(#atoms Zn)
Washer 1
Washer 2
2. The washers analyzed in this experiment have a specification for zinc coating thickness of 0.055 ± 0.0 I0 mm.
According to your data, do your washers conform to the specifications for Zn layer thickness?
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Part B:
1. From a blank Excel worksheet, create a spreadsheet table showing the number of washers, the mass readings
and the volume readings obtained in Part B. Label the columns appropriately, including units as necessary.
The data should be recorded with the correct number of significant figures for each measurement.
2. Create an Excel plot of Volume Reading vs. Number of Washers (y vs. x). Plot a trendline on the chart. Show
the trendline equation and R2 value on the chart. From the trendline, determine the average volume of a
single washer (use correct significant figures).
Average Volume of one washer: __________
3. Create an Excel plot of Mass of Washers vs Volume of Washers (y vs. x). Plot a trendline on the chart. Show
the trendline equation and R2 value on the chart. From the the trendline, determine the average density of a
single washer (use correct significant figures)
Average Density of one washer: _____________
4. The washers analyzed in this experiment have a specification for density of 8.3 ± 0.5 g/cm3.
conform to the specifications for density?
Do the washers
Part C:
1. In Excel, enter the entire class’s data from Part C into a table. Use Excel to calculate the average outside
diameter of the RED WASHER and the average deviation from the mean in the measurement.
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QUESTIONS
Experiment 1 C
1. Would the following experimental mistakes cause the calculated thickness of the zinc coating to be higher,
lower, or the same as the actual thickness? Briefly explain.
(a) You used 20 mL of 3M hydrochloric acid instead of 10 mL.
(b) You removed the washer from the hydrochloric acid before the reaction stopped effervescing.
(c) You left the washer in the hydrochloric acid for 30 minutes.
(d) You did not completely dry your washer before measuring its mass.
2. A cylindrical glass bottle 21.5 cm in length is filled with cooking oil of density 0.953 g/mL.
needed to fill the bottle is 1360 g, calculate the inner diameter of the bottle.
If the mass of the oil
3. Calculate the average mass of a single washer from your data in Part A. Use the average density and average
volume you determined in Part B to calculate the average mass of a single washer. How does the average
washer mass for Part B compare with the average washer mass determined in Part A? What, if anything, can
you say about the accuracy of these two averages?
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PRE-LAB QUESTIONS Experiment 1 C
*****BRING YOUR LAPTOP COMPUTER WITH YOU TO LAB****
1.
A steel washer is “galvanized” in order to:
a) make it shiny
b) protect it from corrosion
c) increase the mass of the washer
d) increase the density of the washer
2.
In galvanization, Zinc is used as the coating. Why?
a) It is harder than the underlying steel
b) It is less reactive than the underlying steel
c) It is more reactive than the underlying steel
d) It has a lower melting point than the underlying steel
3. In lab you remove zinc from the galvanized washer by reacting it with hydrochloric acid solution to form
hydrogen gas and zinc chloride in solution. Which balanced equation correctly depicts this reaction?
a) Zn (s) + HCl (l) → H2 (g) + ZnCl2 (l)
b)
Zn (s) + 2HCl (aq) → H2 (g) + ZnCl2 (aq)
c)
2 Zn (s) + 2HCl (aq) → H2 (g) + ZnCl (s)
d)
Zn (s) + HCl (aq) → H2 (g) + ZnCl2 (aq)
4. Find the following information about Zinc from a chemistry handbook or a website (you will need this
information for data treatment). Cite the source(s) of this information by listing the author or editor, book title,
publisher, city of publication, publication date, and page number, for references in print, or the URL and date
accessed, for those on the internet.
Density of zinc: ____________(g/cm3)
Atomic radius of a zinc atom: ____________(pm)
Citation:________________________________________________________________________
5. Use the ruler below to determine the length of this paper clip in centimeters.
number of significant figures is:
a) 3.5 cm
b) 3.88 cm
c) 3.42 cm
d) 4.3 cm
The answer to the correct
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