L07 Chem 151 Lecture Notes - Lecture 11: Molality, Molar Concentration
23 Feb 2017
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Number of sf can change with data that has poor precision i. e. 0. 3557 m +/- . 0022 m -> 0. 356 +/- . 002m. Rejection of a measured value, i. e 16. 38%, 16. 34%, 16. 17% (this is an outlier that will affect deviation) If only 3 trials outliers should not be rejected unless there was a mistake: with 4 trials, if there is an outlier perform a q-test. Calculate the gap between the outlier and the nearest data point. Calculate range distance from the outlier to the furthest data point. If q > data table value, it can be rejected. 90% confidence means that the accuracy will improve with 90% likelihood if q > data table entry. Percentage by mass = mass of solute/mass of solution * 100% For aqueous solutions of low concentration -> solution has a density very close to water, therefore molarity is approximately the molality.
