You have a stock solution certified by a manufacturer to contain 150.0 plusminus

Question

You have a stock solution certified by a manufacturer to contain 150.0 plusminus 0.3 mu.g SO_4^2- /mL. You would like to dilute it by a factor of 100 to obtain 1.500 mu g/mL. Two possible methods of dilution are stated below. For each method, calculate the resulting uncertainty in concentration. Use manufacturer's tolerances in Tables 2-3 and 2-4 for uncertainties. Explain why one method is more precise than the other. Dilute 10.00 mL up to 100 mL with a transfer pipet and volumetric flask. Then take 10.00 mL of the dilute solution and dilute it again to 100 mL. Dilute 1.000 mL up to 100 mL with a transfer pipet and volumetric flask.

Explanation / Answer

Manufacturers tolerance tables are not posted here.

Of the two methods mentioned, b) is more precise because double dilution includes pippeting for two times which results in two consequtive systematic errors, that is error due to inaccurate calibration of pippetes and volumetric flask.

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