Accuracy and Precision

Pages: 4 (501 words) Published: March 25, 2008
Experiment #4
Weighing and Volumetric Techniques – Accuracy and Precision

Abstract
The purpose of this experiment is to become familiar with proper techniques for using the analytic balances, graduated cylinder, burette and pipette and determine which is more accurate and/or precise. In this experiment, the burette and pipette were more exact than the graduated cylinder and the analytic balance gave a very accurate and precise answer.

Results / Report

1) Weighing Copper
Copper sample #: 1
Balance #: 14
Temperature: 22.8EC

Weighing Attempt #Mass of Copper Sample (g)
13.1234
23.1233
33.1235
43.1232

Average Mass
= (3.1234g + 3.1233g + 3.1235g + 3.1232g) ÷ 4
=3.1234g

Standard Deviation

( - )( - )
3.123400
3.1233-
3.1235
3.1232-
Σ =

Or 0.0001

a) Graduated Cylinder b) Pipette Initial Volume (mL)44.7244.91
1st34.819.911st34.989.93
2nd24.909.912nd25.009.98
3rd15.059.853rd15.089.92

( 9.91±0.01 mL + 9.91±0.01 mL + 9.85±0.01 mL ) ÷ 3
= 9.89±0.03 mL

Pipette average
(9.93±0.01 mL + 9.98±0.01 mL + 9.92±0.01 mL) ÷ 3
= 9.94±0.03 mL

3)

Device Initial Mass (g)Final Mass (g)Resulting Water Mass (g) Graduated Cylinder21.529131.29879.7696
Pipette20.567430.49279.9253
Burette21.277931.326110.0482

TRUE VALUES
Density @ 24.3EC = 0.997225g/mL
Volume = Mass ÷ Density
= 9.7696g ÷ 0.997225g/mL
= 9.7968 mL
Pipette
Density @ 23.3EC = 0.997470g/mL
Volume = 9.9253g ÷ 0.997470g/mL
= 9.9505 mL
Burette
Density @ 23.4EC = 0.997446g/mL
Volume = 10.0482g ÷ 0.997446g/mL
=...