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Accuracy And Precision

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)
1 3.1234
2 3.1233
3 3.1235
4 3.1232

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

Standard Deviation

( - ) ( - )
3.1234 0 0
3.1233 -
3.1235
3.1232 -
Σ =

Or 0.0001

2) Burette Readings


a) Graduated Cylinder b) Pipette
Initial Volume (mL) 44.72 44.91
Actual amount added (mL) Actual amount added (mL)
1st 34.81 9.91 1st 34.98 9.93
2nd 24.90 9.91 2nd 25.00 9.98
3rd 15.05 9.85 3rd 15.08 9.92

Graduated Cylinder average
( 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 Cylinder 21.5291 31.2987 9.7696
Pipette 20.5674 30.4927 9.9253
Burette 21.2779 31.3261 10.0482

TRUE VALUES
Graduated Cylinder
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
=...