1. TOLERANCES OF GRADUATED EQUIPMENT
Tolerances are usually larger than ±1 in the last decimal place
Tolerances are often provided by the manufacturer
5-mL Volumetric Pipet : ± mL
50-mL Volumetric Buret : ± mL
100-mL Volumetric Flask : ± mL
A tolerance in the hundredths place means the measurement should be given to the hundredths place
Reading for a 5-mL Volumetric Pipet :
5.00 mL
Expected range for the measured value :
4.98 mL to mL
5.00 ± 0.02 mL
EX2-1 (of 11)

2. READING GRADUATED EQUIPMENT
For all measurements, the last digit recorded is an estimated digit
EX2-2 (of 11)

3. Most Accurate Graduations:
One Celsius Degree
Estimated digit:
Tenths
Reading :
47.6 Cº
EX2-3 (of 11)

4. Most Accurate Graduations: One-Tenth of a Milliliter
Estimated digit:
Hundredths
Reading :
9.36 mL
1.41 mL
EX2-4 (of 11)

5. Most Accurate Graduations:
One Milliliter
Estimated digit:
Tenths
Reading :
60.0 mL
EX2-5 (of 11)

6. Most Accurate Graduations:
One Celsius Degree
Estimated digit:
Tenths
Reading :
42.0 Cº
EX2-6 (of 11)

7. Most Accurate Graduations:
One Milliliter
Estimated digit:
Tenths
Reading :
81.5 mL
EX2-7 (of 11)

8. Most Accurate Graduations: One-Tenth of a Milliliter
Estimated digit:
Hundredths
Reading :
24.16 mL
EX2-8 (of 11)

9. ACCURACY AND PRECISION
ERROR – The difference between a measured value and the “true” value of a property
ACCURACY – The agreement between a measured value and the “true” value
Measured values close to the “true” value are ACCURATE
EX2-9 (of 11)

10. ACCURACY AND PRECISION
, but values are “accepted” if they are derived from repeated measurements (density of alcohol at 25°C: g/mL)
It is rare to know the “true” value of property
EX2-10 (of 11)

11. ACCURACY AND PRECISION
PRECISION – The agreement among several measured values of the same quantity, and reflects the reproducibility of a given measurement
Measured values close to the each other are PRECISE
EX2-12 (of 11)