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Chem 120, Prelab Questions
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Quiz Section No.:
EXPERIMENT 1 – DENSITY
PRE-LAB EXERCISE
Make sure to report ALL numbers with correct units and the
proper number of significant figures indicated.
1. While working in your garden one day, you find an old leather pouch containing coins
that are various shades of grayish/silver in color. You have a balance and a
graduated cylinder, so are able to make observations about the mass and volume of
each coin. What material do you suspect each coin to be? (Refer to Table 1-1 in your
lab manual.) Show your calculations in the space provided below.
Coin #
Measured
Mass (g)
Measured
Volume (mL)
Coin 1
52.5
2.43
Coin 2
10.8
1.00
Coin 3
30.5
4.34
Coin 4
38.2
3.40
Density (g/mL)
Type of Metal
Chem 120, Prelab Questions
Name:
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Quiz Section No.:
2. You need to determine the density of an irregularly-shaped object that has a mass of 4.55 g. You
carefully place the object in a graduated cylinder containing 19.4 mL of water and find that the
volume is displaced to 23.1 mL. What is the density of the object?
3. You are a technician in a lab. A colleague tells you that there have been problems
with the 25.0-mL samples you have been providing. Data collected suggests that the
samples are smaller than 25.0 mL. You know that you have been measuring the
volume carefully, and reading the meniscus correctly, so you decide to check the
calibration of the graduated cylinder you’ve been using.
a. You fill the graduated cylinder with water at 25oC up to the 25.0 mL mark,
and then measure the mass of this volume of water. You find that the mass is
22.4 g. The density of water at 25oC is 0.99704 g/mL. What is the actual
volume of the water?
b. What is the percent error in your measurement if the cylinder is reading 25.0
mL but actually delivering the volume you calculated in part a? (Note: the
percent error may be negative, in which case do not forget to include the
negative sign.)
c. Does your measurement indicate an acceptable level of accuracy?