CHEM 20L Lecture Notes - Lecture 26: Vacuum Distillation, Eutrophication, Boiling Point
11 Apr 2016
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Accuracy (closeness to true value) vs. precision (closeness of a set of results to each other) Absolute error must always have the same number of decimal places as the measurement. For inding error: muliplicaion/division where ab=c or a/b=c: relaive error: c/c = a/a + b/b, absolute error: c= ( a/a + b/b)c. For inding error: addiion/subtracion where a+b=c or a-b=c: relaive error: c/c = a/c + b/c, absolute error: c/c = ( a/c + b/c)c. Volumetric glassware will always measure to the hundredths decimal place, thus any errors/calculaions are limited to 2 igures ater decimal regardless of sig ig rules. Concentraion may be measured in molarity (moles solute/liters soluion), w/v% (g solute/100 ml soluion), ppm (mg/liter soluion), ppb ( g/liter soluion) May analyze samples through gravimetric, volumetric, or spectrophotometric (beer"s law) When using beer"s law, you may dilute a concentrated soluion, and use a blank to rid of background interference (the blank allows the graph to start at 0,0.
