8. 20.00 ml of a reagent are dispensed using a 10.00 mL Class A pipet with a pub

Question

8. 20.00 ml of a reagent are dispensed using a 10.00 mL Class A pipet with a published uncertainty of 10.00 + - 0.02 mL. Interestingly, when the pipet was calibrated ten times, its mean Volume and standard deviation was found to be 0.9992 + - 0.006 mL. Determine the Uncertainty in delivering the 20 mL 1st using the manufacturers data and then Using the calibration results. Which gives better precision? And is it therefore true that calibrating a pipet allows us to decrease the uncertainty in its delivered volume?

Explanation / Answer

According to the published uncertainity the precision of values in pippetting 20ml of reagent lies between 19.96ml to 20.04ml with an error range of about -0.04 to +0.04

where as on calibrating the pipette the precision of values in pippeting of 20ml of reagent lies between 19.972ml to 19.996ml with an error range of-0.004 to -0.028 .

hence calibration gives better precision and it is true that calibrating decreases the uncertainity in delivered volume.

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