# Final Exam Quant Review

 Molality (moles solute)/(kg solvent) ppm (μg sample)/(mL solute)(mg sample) / (L solute) When dealing with concentration problems, what are top three key things to think about? 1) Density, concentration, molartiy... etc. of the solvent, solute and all else. Sometimes these do not correlate. Watch out for it!2) Think of when to use M1V1 = M2V2 rule. It is normally for getting a volume to a desired molarity. (Left side is moles taken from concentrated solution, and right side is moles placed in dilute solution)3) Think of it like a puzzle, or stoichiometry stuff :) Kilo to pico Kilo (1000)Hecto (100 - h)Deca (10 - da)Deci (.1)Centi (.01)Mili (.001)Micro (.000001)Nano (.000000001)Pico (.000000000001) What are the steps in chemical analysis? -inject solution into chromatogram-wash with solvent to flush it through column-chromatogram separates analytes What does it mean to mask an interfering species? It means that a reagent is used that react with the interfering species, to prevent detection. What is the difference between random and segregated heterogeneous material? Random: differences in composition, appear randomly and on a fine scaleSegregated: large regions have obvious different compositions ppb (ng sample) / (mL solute)(μg sample)/(L solute) Calculating quantities of reagents needed to prepare solution M1V1 = M2V2(moles taken from concentrated solution) = (moles added to dilute solution) Uncertainty in Addition and Subtraction from Absolute Values e4 = √e12 + e22 + e32 e = uncertainty valueabsolute uncertainty = actual valuerelative uncertainty = wt% or fraction Uncertainty in Multiplication and Division e4 = √(%e1)2 + (%e2)2 + (%e3)2 e = uncertainty valueYou have to convert to relative uncertainty first! Significant figure rule for ubcertianties First digit of absolute uncertainty is the last significant figure of answer Significant figures when taking log of something or solving log log339 = 2.530 (mantissa takes sig figs)104.36 = 2.3 x 104 How are uncertainties in atomic masses obtained? 2C = 2(12.0106 (± 0.0010))2C = 24.0210 ± 0.0024H = 4(1.00798 (± 0.00014))4H = 4.03192 ± 0.00028 So all the above uncertainties were multiplied by 2 then use the addition / subtraction rules to add them How does the uncertainty change for a calibrated and uncalibrated pipet? Uncalibrated - multiply uncertainty by number of deliveriesCalibrated - addition / subtraction rule Coefficient of variation Stdev expressed as a percentage of the mean value. Also known as the relative stdev. What does it mean to find the area of a certian range? Using the z chart, it is also the probablitity of measuring z in a certian range. z = (x - xavg) / s Using the F test Answers: Is s from the instrument "significantly" greater than s from original instrument. Fcalculated = s12 / s22The larger stdev is in the numerator. If Fcalc > Ftable then there is a significant difference. This is because there is 5% probability of finding F above the table value. The significant difference means the null hypothesis is rejected and the values probably come from different populations. Null Hypothesis Two sets of data are drawn from populations with the same properties. There are no significant differences between populations. Rejected if there is less than 5% probability of finding observed value. Confidence Interval Tool used to test probability of finding a range of values within a given location. You get t from a chart. Just plug and chug the values in Comparing a measured result with known result. Given: -set of values or mean -commercial value. Calculate the confidence interval of 95% and then see if the commercial value agrees with it. Grubbs test To see if a value should be part of the measurements. Gcal = (questionable value - avg) / stdev How would your compare replicate measurements? Found from F test (p.76) Significantly Different: use a more complicated it test that pools it all togetherNot Significantly Different: conduct a t test AuthorDianaKarlova ID319781 Card SetFinal Exam Quant Review DescriptionQuantitative Analysis Exam Review Updated2016-05-05T06:46:59Z Show Answers