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Prelab1.2

# Prelab1.2 - Divide absolute value of difference between...

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Uncertainty in Analytical Data Buret Volume: ± 0.01 mL Balance Weight: ± 0.0001 g Pipet Volume: ± 0.03 mL (in 25 mL) Random Variations : Average to zero. Average (Mean) of many determinations gives true (correct) result. Outliers : Appear to deviate by more than random variations. Reject or not? Reject if known error in procedure, or if one of first few "trial runs". Otherwise - statistical treatment.

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Q-Test (SWHC 7C) Six M NaOH determinations: 0.08907, 0.1068, 0.1061, 0.1072, 0.1089, 0.1065 Reject trial run (0.08907). Arrange remaining results in order: 0.1061, 0.1065, 0.1068, 0.1072, 0.1089
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Unformatted text preview: Divide absolute value of difference between questionable value and nearest neighbor by spread: Q exp = 0.1089 " 0.1072 0.1089 " 0.1061 = 0.61 Find Q in table on page 161: Q 90,5 = 0.64 If Q exp > Q table , then you may reject data. Significant Figures Report all results to FOUR significant figs. Example: M KHP = 7.4307 g 204.23 g/mol 0.2500 l = 0.14553591539 Round off to 0.1455 M Range : Expt. 1 and 2 should be ≤ 4 ppt Absolute range = Highest - Lowest Relative Range = Highest - Lowest Average x 1000 ppt Example: Rel. Range = 0.1089 - 0.1061 0.1071 x 1000 = 26 ppt...
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