Part 1 Flashcards
die
Explain how temperature variation can affect the accuracy of glassware calibration.
Temperature variations can affect glassware calibration because both the glass and the water used for calibration expand and contract with temperature.
How variations in the material and manufacturing process of glassware can affect its calibration?
The type of glass used in the glassware can affect how much it expands with temperature. Borosilicate glass has a relatively low thermal expansion coefficient, minimizing the impact.
Uneven wall thickness caused by imperfections can lead to slight volume differences within the markings.
Impurities in the glass can also influence how it expands and contracts with temperature, making it deviate from the standard used for calibration.
Finally, even slight inaccuracies in the markings themselves can introduce errors in volume measurement
Analyze the cumulative effect of small systematic errors in the calibration of a pipette. How would these errors propagate through multiple steps in a complex titration experiment?
Small systematic errors in pipette calibration can leading to significant miscalculations in the final result. The error in concentration increases with each titration step.
Describe how you would use statistical methods to validate the calibration results of a set of 10 mL volumetric flask.
Perform multiple calibration trials (e.g., 5-10) for each flask.
For each flask, calculate the average volume delivered (mean) across all its calibration trials. Additionally, calculate the standard deviation (SD).
Evaluate spread.
Compare to nominal value.
Calculate confidence intervals for 90% and 95%
Analyze how improper handling and storage of glassware can affect its calibration. Provide recommendations for the proper handling and storage practices to maintain calibration accuracy
Mechanical Damage: Bumps, drops, or scratches on the glassware can cause minor deformations
Chemical Contamination: Exposure to harsh chemicals or improper cleaning can leave residues on the glassware.
Thermal Shock: Sudden temperature changes can cause stress fractures or warping.
A 50 mL burette is filled with distilled water at 25 C and delivers 48. 75 grams of water. Calculus the actual volume of water delivered by the burette. (Density 0.99707 g/mL)
48.89 mL
A 100 mL volumetric flask is calibrated and found to contain to contain 100.25 mL when filled to the mark. Calculate the percentage error of the flask
0.25%
A 25 mL pipette is calibrated at 20 C and delivers 24.80 grams of water. The calibration must be corrected to 25 C where the density of water is 0.99707 g/mL (density of water at 20 C is 0.99823 g/mL). Calculate the corrected volume.
24.87 mL
Calculate the combined uncertainty for a 10 mL pipette calibration where the uncertainties are balance (+ 0.01 g), temperature (+ 0.05 C), and volume reading (+ 0.02 mL). Assume the density of water uncertainty is negligible.
+ 0.05
A 50 mL burette is calibrated gravimetrically and delivers 49.50 grams of water at 22 C. If the density of water at 22 C is 0.99777 g/mL. Calculate the delivered volume
49.61 mL
A volumetric flask calibrated for 20 C is used at 30 C. If the coefficient of volumetric expansion for the glass is 9 x 10^-6 /C, calculate the corrected volume of a 100 mL flask.
100.00009 mL
A technician reads the meniscus of 0.05 mL above the actual mark on a 25 mL pipette. Calculate the percentage error introduced by reading this error.
0.2%
In a series of calibrations, a 10 mL pipette consistently delivers 10.02 + 0.03 mL. Determine the relative standard deviation RSD and interpret the precision of the pipette
10.02 (+0.3%) mL
If a titration experiment involves 5 pipetting steps, each with a systematic error of 0.05 mL in a 10 mL pipette, calculate the total systematic error.
0.25 mL
A laboratory uses a 100 mL volumetric flask 4 times a day. Previous records show a 0.1% volume drift every 500 uses. Calculate how often the flask should be recalibrated.
125 days or 4 months
