Learning Objective
To calibrate the given volumetric apparatus and investigate errors in volume measurement.
Introduction
Proper calibration of volumetric apparatus is essential to obtain accurate results in scientific experiments. Calibration checks how precisely an apparatus can measure a volume, and it is a key part of achieving reliable results.
Calibration ensures the precision of scientific instruments. Even the slightest errors in calibration can significantly affect the outcomes of an experiment. Standard glassware is typically used to minimize errors, although these apparatuses still require regular calibration to provide accurate measurements.
Glassware used in laboratories is often made from Borosilicate glass because it is highly durable and resistant to thermal and chemical changes.
- Transparent and easy to observe
- Available in various sizes and shapes
- Can be molded, cut, and bent
- Low thermal coefficient of expansion
- Resistant to chemical attacks
- Stable at high temperatures
Accuracy refers to how close a measured value is to the true value, while Precision indicates how closely multiple measurements agree with each other. Error is the difference between the actual and observed readings.
Apparatus
- Measuring Cylinder
- Burette
- Pipette
- Beaker
- Electronic Balance
- Burette Clamp
Procedure
- Weigh a 100mL beaker to the nearest 0.01g (W1)
- Using a 10mL measuring cylinder, carefully deliver 10mL of water into the beaker. Re-weigh the beaker (W2)
- Determine the mass of water delivered: W3 = W2 - W1
- If the density of water is 1.00 g/mL, calculate the volume of water delivered (V1) using the formula: Volume = mass / density
- Calculate the difference between the delivered volume and the expected true volume: V2 = V1 - 10
- If the delivered volume does not match the expected true value, suggest possible reasons for the discrepancy.
- Discuss ways to reduce random errors in the experiment.
- Repeat the procedure for other devices like the Measuring Cylinder (25mL), Burette (50mL), and Pipette (5mL).
- Analyze and tabulate the data.
- Comment on the experiment and summarize your findings.
Experiment Image
Observations and Calculations
| Trial # | W₁ (g) | W₂ (g) | W₃ = W₂ - W₁ (g) | V₁ = W₃ / D (mL) | V₂ = V₁ - 10 (mL) |
|---|---|---|---|---|---|
| 1 | 51.54 | 61.31 | 9.77 | 9.77 | -0.23 |
| 2 | 51.54 | 61.30 | 9.76 | 9.76 | -0.24 |
| 3 | 51.54 | 61.35 | 9.81 | 9.81 | -0.19 |
Statistical Analysis
Mean Volume V = (9.77 + 9.76 + 9.81) / 3 = 9.78 mL
Percentage Error = {(9.78 - 10) × 100} / 10 = -2.2%
The measurements contain an error of approximately -2.2%.
Explanation
The observed measurement discrepancies may result from several factors including:
- Instrument calibration inaccuracies
- Mechanical loss during liquid transfer
- Improperly dried equipment
- Measurement parallax errors
- Environmental temperature variations
Conclusion
This experiment demonstrates significant measurement instrument variance that impacts result accuracy. The -2.2% systematic error indicates the need for:
- Regular equipment calibration
- Proper measurement techniques
- Environmental condition control
- Multiple trial verification
Implementing these quality control measures can substantially improve measurement precision in future experiments.
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