LEARNING OBJECTIVE:
To calibrate the given volumetric apparatus and to investigate errors in volume measurement
INTRODUCTION:
The quantitative estimation of various apparatus is an essential requirement. Therefore, there is a need for the proper calibration of these glasswares to get more accurate results.
What is calibration? Calibration is the precision of an instrument and the calibration process is used to check how precisely an apparatus can measure a volume. Accuracy is an important factor in analysis because even the slightest error can greatly affect the experiment. This is the reason why standard glassware is used, but these apparatuses also fail to provide exact reading or estimation. For any experiment to achieve perfect results errors must be taken into account.
Glasswares are the apparatuses or pieces of equipment used for scientific work, experiments, or projects. These glasswares are made of Borosilicate glass.
Glass is used for scientific work because they
- are transparent
- available in a range of sizes and shapes
- can be cut, bend and mold
- have a low thermal coefficient of expansion
- have high resistance to chemical attacks
- possesses stability at high temperature
ACCURACY is the degree of closeness of the observed value to the actual value.
PRECISION is the degree of closeness of two or more than two values to each other.
ERROR is the difference in the actual and observed reading.
APPARATUS:
PROCEDURE:
- Weigh a 100mL beaker to the nearest 0.01g (W1)
- Using the selected 10mL measuring cylinder as carefully as possible deliver 10mL of water from the cylinder into the beaker. Re-weigh the beaker (W2).
- Determine the mass of water delivered W3 = W2 - W1
- If the density of water is taken to be 1.00 g/mL, then calculate the volume of water delivered V1 by using the formula Volume= mass/density.
- Calculate the difference between the volume delivered and expected true volume V2.
- If the volume delivered does not equal the expected true value suggest possible reasons for the observed difference?
- The Value obtained in V2 almost certainly contains random errors. How could the effect of random error be reduced?
- Repeat the procedure for other devices i.e. Measuring Cylinder (25mL), Burette (50mL), and Pipette (5mL)
- Analyze and tabulate the data.
- Comment on the experiment.
OBSERVATIONS AND CALCULATIONS:
*The experiment was performed in the lab and the following stats were observed
Weight of dry beaker = W1 = 51.54 g
Density of water = D = 1.0 g/mL
Measuring Cylinder 10mL
|
Sr # |
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 |
61.3 |
9.76 |
9.76 |
-0.24 |
|
3 |
51.54 |
61.35 |
9.81 |
9.81 |
-0.19 |
Mean Volume V = (9.77 + 9.76 + 9.81) / 3 = 9.78 mL
Percentage Error = {(9.78 - 10) * 100 } / 10 = -2.2 %
The reading contain an error of about -2.2 %.
EXPLANATION:
The error in the reading may occur due to many reasons such as faulty apparatus, poor calibration, mechanical loss while transferring chemical or beaker may not be properly dried.
CONCLUSION:
The experiment shows that there is some sort of error in the measuring instrument which cannot be neglected while performing the experiment because these can cause great variation in the results. Therefore, we must take into account proper precautions and techniques to minimize the effect of this error to get accurate readings.
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