More on “Signal” Interference Method blank Matrix effect Detection limit

The “Scales” of Analytical Chemistry

Review Significant Figures What are sig figs? Rules: Addition/subtraction Multiplication/division Log/antilog Exact numbers When to round?

Significant Figures Examples Add the numbers , 7.113*10 -2, and 0.81 How many kilometers is 9.3 miles? (Use the conversion factor 1 km = mi.) A student measures the mass and volume of a liquid to determine its density. The volume is mL. An empty beaker has a mass of g, and the beaker with liquid is g. What is the density? What is the pH of a 1.56*10 -3 M hydrochloric acid solution?

Accuracy What is accuracy? Quantifying accuracy Assessing accuracy No true value?

Precision What is precision? Quantifying precision Assessing precision

Characterizing Data Example Calculate the average, mode, standard deviation, relative standard deviation, and percent relative error for the following data set (density of pennies, post 1982 = 7.18 g/mL). (By hand first, then use your calculator’s stat mode…) g/ml g/ml g/ml g/ml

Two Types of Error 1.Determinate error – Sampling – Method – Measurement – Personal **can be constant or proportional**

Class A Tolerances

Two Types of Error 2.Indeterminate/random Visualizing these: DeterminateIndeterminate

Uncertainty What is uncertainty? DUI example

If you don’t learn anything else in this class…