SUPL
‐
001 – Problems
1. A student reports the following data in several determinations of the density of a
homogeneous solid plastic sphere.
RUN 1
RUN 2
RUN 3
RUN 4
Mass of Sphere (g)
8.30
8.34
8.25
8.32
Volume of Sphere (mL)
6.3
6.4
6.3
6.6
[Should we view this as 4 independent determinations of density or as 4
determinations of mass and 4 independent determinations of volume?
Since the experimental determinations of mass and volume are
independent experimental processes, the latter seems the appropriate way
to view the data.
So, we can calculate the averages of the measurements of mass and
volume and compute the density from those quantities.]
a. How should the student report the mass of the sphere? What is the percent
deviation?
M
avg
= (8.30 + 8.34 + 8.25 + 8.32) / 4 = 8.30 g
Avg dev = (0.00 + 0.04 + 0.05 + 0.02) / 4 = .03 g
The mass of the sphere is:
8.30
±
0.03 g
Pct dev = 100 X 0.03 / 8.30 = 0.4 %
b. How should the student report the volume of the sphere? What is the percent
deviation?
V
avg
= (6.3 + 6.4 + 6.3 + 6.6) / 4 = 6.4 mL
Avg dev = (0.1 + 0.0 + 0.1 + 0.2) = 0.1 mL
The volume of the sphere is:
6.4
±
0.1 mL
Pct dev = 100 X 0.1 / 6.4 = 2 %
c. How should the student report the density of the sphere? What is the percent
deviation?
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
This is the end of the preview.
Sign up
to
access the rest of the document.
 Spring '09
 RALEIGH
 Chemistry, pH, 0%, Vavg, dmax, MAVG, Davg

Click to edit the document details