Full set of Notes with Fill-Ins - San Jose State University

Chem 155 Unit 1 Page 50 of 3161.1.25 Calculating Conc. w/ Standard Additions:a'ab'bOne way of analyzing this uses similar triangles:a / b =a’/b’The y-axis absorbance signal (S) is proportional to the moles ofanalyte (V X C X ) and standard (V S C S ).The x-axis is simply the standard ‘spike’ volume.The x-intercept is the hypothetical spike volume (V S ) 0 containing thesame amount of analyte as the sample.a is proportional to moles of analyte in the sample = V X C Xa’ is proportional to moles of std added = V S C Sb is (V S ) 0 – the x-intercept of the graphb’ is V S – the spike volumeSubstitute for a,a’,b,b’:V X C X(V S ) 0=V S C SV SSolve for C X :C X = C S (V S ) 0 /V XPage 50 of 316