Experiment 2: Precision and Accuracy of Measurements
Mara Tolksdorf
Lab Partner: Elizabeth Ham
CHEM 1211K-C07
Crystal Bell
I did not copy this work from any other students; current students or old lab reports.

Objective:
The overall purpose of this experiment is to determine the precision and accuracy of
different instruments in the lab, what is best used when. This lab requires knowledge of
identifying the different instruments: glassware (graduated, serological, and volumetric),
balances, and mass spectrometers, how to use them, and how to read them properly. The
goal is the be able to apply the concepts of accuracy and precision.
Data/Results
:
Sample Calculations:
1. Concentration of Kool-Aid Solution Made in 100mL Volumetric Flask
(100mL/1)*(1L/1000mL)=0.1L
M=mol/L
(0.10g/1)*(1mol/10000g)=0.00001mol
0.0001M blue Kool-Aid
2. Concentration of Solution in Test Tube #1M1V1=M2V2; where M1=(1.00*10^-4) and V2=.005L and V1=0.001LM2=0.00002M (concentration of Test Tube #1)Part A. When is a gram, a gram?

Mass of
Beaker
and
Water
(g)
Mass of
Water
Delivere
d (g)
Calculate
d Volume
of Water
Delivered
(mL)
0
101.272
g
--
--
10
111.140g
9.868g
9.889mL
20
120.891
g
9.751g
9.772mL
30
130.538
g
9.647g
9.668
Mean= 9.776mL
SD=0.111mL
Mean and Standard Deviation of Water Delivered with a Serological Pipet (Table 6.)
Nominal
Volume
of Water
(mL)
Mass of
Beaker
and
Water
(g)
Mass of
Water
Delivere
d (g)
Calculate
d Volume
of Water
Delivered
(mL)
0
101.258
g
--
--
10
110.877g
9.619g
9.640mL
20
120.575
g
9.698g
9.719mL
30
130.242
g
9.667g
9.688mL
Mean=9.682mL
SD=0.040mL
Mean and Standard Deviation of Water Delivered with a Volumetric Pipet (Table 7.)
Nominal
Volume
of Water
(mL)
Mass of
Beaker
and
Water
Mass of
Water
Delivere
d (g)
Calculate
d Volume
of Water
Delivered

Discussions:The objective for Part A. of the experiment is to determine not only the accuracy across multiple packets of sweetener but also the precision for multiple balances. The goal is to become acquainted with how to decipher measurements in the laboratory, to knowingly obtain the best measurement of data possible for a given set and distinguish between accuracy and precision.The objective for Part B. of the experiment is to become familiar with glassware in the laboratory and determine how accurate the glassware is. This becomes important to determine what instrumentation is necessary not only to perform the experiment but also obtain accurate results.The objective for Part C. of the experiment is to apply the skills from Part B. by making a stock solution and then diluting it. Diluting a solution requires measuring all the data accurately: gram amount, water volumes, and stock solution volumes. Knowing what glassware is best to use and how to use it becomes significant. Part A.The precision of the one packet measured with different balances (Table 3.) is very precise with a standard deviation of only 0.000707g. There is less precision of the five different packets measured on one balance (#2, Table 2.) Table 3. is more precise than Table 2. because there is less variance in the range of data points. That means that the balance in the laboratory is more precise than the instrument that dispenses the contents of the packets at the factory. The variation of the data points for Table 2. most likely