# Lab #2 - CHEMISTRY 1211K Section B-05 Precision and...

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CHEMISTRY 1211K Section B-05 Precision and Accuracy of Measurements Honor Code: 09/13/2013
I. D ATA Section A : When is a Gram a Gram? Mass of empty packet of sweetener: 0.253 g (± 0.002 g) Nominal mass of sweetener: 1 g Number of balance used: #1 Table 1: Mass of five different packets of sweetener weighed on balance number 1. Trial No Mass of sweetener in grams (±0.002 g) Percent error 1 1.070 g 7.290 % 2 1.097 g 7.110 % 3 1.140 g 6.842 % 4 1.057 g 6.149 % 5 1.047 g 5.253 % Average mass of sweetener in grams: g Standard deviation of five measurements: g Table 2: Mass of one packet of sweetener weighed on five different balances. Balance No Mass of sweetener in grams (±0.002 g) Percent error 1 1.029 g 3.596 % 2 1.030 g 3.689 % 3 1.029 g 3.596 % 4 1.029 g 3.596 % 5 1.025 g 3.220 % Average mass of sweetener in grams: g
Standard deviation of five measurements: g Section B : Measuring Liquids Volume (mL) Smallest Graduation (mL) Estimated Precision (mL) 25 0.5 ± 0.01 100 1 ± 0.1 1000 10 ± 0.1 Table 3: Precision of 25, 100 and 1000 mL graduated cylinders. Table 4: Mass of 10 mL of water delivered by a 10 mL graduated cylindered. Theoretical Volume (mL) Total mass measurement (g) Calculated mass of added water (g) Calculated V 10 116.428 9.710 9.73 20 126.085 19.420 19.4 30 135.708 29.043 29.1 Average volume delivered by a 10 mL graduated cylinder: mL Standard deviation of measurements: mL Table 5: Mass of 10 mL of water delivered by a 10 mL serological pipette. Theoretical Volume (mL) (±0.06 mL) Total mass measurement (g) (±0.002 g) Calculated mass of added water (g) Calculated V 10 116.428 9.763 9.7 20 126.014 19.349 19.3 30 135.644 28.979 29.0 Average volume delivered by a 10 mL serological pipette: mL Standard deviation of measurements: mL Room Temperature: 21.5 o C
Density of water: 1.000 kg/mL Table 6: Mass of 10 mL of water delivered by a 10 mL Grade A volumetric pipette.