This preview shows pages 1–7. Sign up to view the full content.
This preview has intentionally blurred sections. Sign up to view the full version.
View Full DocumentThis preview has intentionally blurred sections. Sign up to view the full version.
View Full DocumentThis preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
Unformatted text preview: Introduction Page 1 of 2 What is Analytical Chemistry? The branch of chemistry dealing with the identification and quantitation of species in a given sample  Qualitative (What)  Quantitative (How much) Chemical Analysis "Wet" Methods Instrumental Methods Gravimetric Separation Volumetric Optical E l e c t r o c h e m i c a l Measuring is not the only thing Analytical Chemists do ¾ Develop new methodologies and instruments ¾ Proper sampling, sample handling and preparation ¾ Calibration and standardization ¾ Data interpretation, classification, fitting Introduction Page 2 of 2 Examples of "Wet" Methods : 1. Ag + + Cl> AgCl Mass (Gravimetry) 2. H + +  OH > H 2 O Volume (Titrimetry) 3. Unknown + dye > Color Qualitative Anal. http://www.cbs.com/primetime/csi/ Examples of Instrumental Methods : Optical : F e 3+ + Ligand > Fe(L) 3 3+ Ö Colorimetric Determination Electrochemical : P b 2+ + 2e> Pb (At Indicator Electrode) Ö Application of Potential yields Charge Chromatography : SizeExclusion Chromatography > Protein Fractionation and Identification Ö Separation allows Specific analysis Measurement and Errors Page 1 of 13 Measurement and Errors Every measurement has associated with it an uncertainty . • Measuring the width of a room with a tape measure may be fine, but using a tape measure to obtain where the center of a 1 cm rod is, would not be. (See accuracy and precision later.) Rule of Thumb Ö Always estimate the measured value to 10% of the distance between scale divisions. Example: A ruler with 1mm divisions should be read to within 0.1mm or value ± 0.1mm. Of course this is subjective, but the error should incorporate the uncertainty. ) When we start manipulating numbers, when should we keep or throw away part of the answer? Measurement and Errors Page 2 of 13 Significant Figures minimum number of digits necessary to write a value in scientific notation without loss of accuracy. ) 103620900 Q: How many significant figures? A: HUH?!! Zero Rules 1. Significant if in the middle of two sig digits 2. Significant if to the left of a decimal point and to the right of a number 3. Significant in scientific notation NUMBER #Sig Figs (s.f.) 103620900. 9 3.765 x 105 4 3.7650 x 105 5 0.00003675 4 Measurement and Errors Page 3 of 13 How do we determine the # of significant figures when we add, subtract, multiply, divide, etc.? Add or subtract 1.6392 (five sf) 46.231 (five sf) 47.870 2 < the 2 is not significant the correct answer is 47.870 Multiply or divide 20.962 (five sf) x 1.050 (four sf) 22.01 01 < the 01 is not significant the correct answer is 22.01 (four sf) Rounding 12.815 12.815 + 3.60 + 3.61 16.41 5 16.42 5 answer is 16.42 answer is 16.42 Measurement and Errors Page 4 of 13 THE RULES!...
View
Full
Document
This note was uploaded on 10/06/2009 for the course CHEM 2001 taught by Professor Staff during the Spring '08 term at LSU.
 Spring '08
 Staff
 Analytical Chemistry

Click to edit the document details