Using the typical values shown in the table above calculate the relative uncerta

Question

Using the typical values shown in the table above calculate the relative uncertainty for each of the measurement methods.For each of the five physical quantities listed in the table above which measurement has the smallest relative uncertainty.

38 Table 2.2 Representative measurement methods PhysicalMethod Typical Approximate valueuncertainty quantity Mass Volume analytical balance microbalance pipet, Class A volumetric flask, Class A pycnometer, 25-mL capacity magnetic float densimeter vibrating-tube densimeter mercury manometer or barometer diaphragm gauge 100g 0.1 mg 20mg 0.1g 10 mL0.02mL 1 L 0.3 mL 1 gmL 2mg mL-1 l gmL 0.1 mg mL-1 1gmL-1 0.01 mg mL-1 760 Torr 100 Torr Density 0.001 Torr 1 Torr Pressure Temperature constant-volume gas thermometer 10K 0.001 K mercury-in-glass thermometer platinum resistance thermometer monochromatic optical pyrometer 300 K 300K- 1300 K 0.01 K 0.0001 K 0.03 K

Explanation / Answer

Mass:

- analytical: relative uncertainty= 0.0001g/100g= 1x10-6

- microbalance: RU= 0.0001mg/20mg= 5 x10-6

Volume:

-pipet: RU= 0.02mL/10mL= 2x10-3

-volumetric flask: RU= 0.0003L/1L = 3x10-4

Density:

-pycnometer: RU= 0.002g/mL/1g/mL= 2x10-3

- magnetic float densimeter: RU= 0.0001g/mL/1g/mL= 1x10-4

- vibrating-tube densimeter: RU= 0.00001g/mL/1g/mL= 1x10-5

Pressure:

-mercury manometer: RU= 0.001torr/760torr= 1.32x10-6

-diaphragm gauge: RU= 1torr/100torr= 0.01

Temperature:

- constant-volume gas thermometer: RU= 0.001K/10K= 1x10-4

-mercury-in-glass thermometer: RU= 0.01K/300K= 3.33x10-5

-platinum resistance thermometer: RU= 0.0001K/300K= 3.33x10-7

-monochromatic optical pyrometer: RU= 0.03K/1300K= 2.3x10-5

The smallest relative uncertainty is the one of the platinum resistance thermometer.

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