14Chapter OneChemicalFoundationsPrecision is an indication of accuracyonly if there are no systematic errors.Leading zeros are never significantfigures.Captive zeros are always significantfigures.Trailing zeros are sometimes significantfigures.Exact numbers never limit the number ofsignificant figures in a calculation.Following are the results of five trials:VolumeShownbyVolumeShownTrialGraduatedCylinderby the Buret125mL26.54mL225mL26.51mL325mL26.60mL425mL26.49mL525mL26.57mLAverage25mL26.54mLIs the graduated cylinder accurate?SolutionThe results of the trials show very good precision (for a graduated cylinder). The studenthas good technique. However, note that the average value measured using the buret is sig-nificantly different from 25 mL. Thus this graduated cylinder is not very accurate. It pro-duces a systematic error (in this case, the indicated result is low for each measurement).
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