Chem 210 Final Exam Questions with 100% Correct Answers

Calculate volume 0.2 NaOH and # equivalence points for titration of 25mL 0.1 H3PO4 - 2 eq points- 0.1M x 0.025L = 0.0025 mol H3PO4 mol H3PO4 = mol added NaOH 0.0025 mol NaOH / 0.2 M = 0.0125 L NaOH added Calculate equivalence point volumes for titration of 25.00 mL of 0.060 M HCl and 0.10 M H3PO4 with 0.075 M NaOH - exp 1 calculations find moles total acid, response factor - Coefficient that makes the relative response of a detector to analyte and the internal standard the same. equation to find unknown amount analyte using RF - (amount ethanol / amount IS) = (area ethanol / area IS) x RF Equation for number of theoretical plates - N = 5.55 x (tr^2 / w1/2^2) HETP equation - L / N Principle components of a GC - Mobile phase reservoir -- [Sample injector -- stationary phase -- Detector] -- readout OVEN in brackets Quantities on x and y axes in a chromatogram - x axis - retention time (min) y axis - detector response All strong acids - HCl, HBr, HI, HNO3, HClO4, H2SO4 molecular weight and boiling point of ethanol - 46.07 g/mol 78.37 degrees molecular weight and boiling point of 1-butanol - 74.12 g/mol 117.40 degrees C Calculate RF for mixture containing ethanol: 8.0 x 10^-5 M with an area of 122,000 1-butanol:6.4 x 10^-5 M with an area of 172,000 - 1.76 desirable qualities for IS in GC - similar in structure to analyte but not present under analysis 2 advantages of using IS over a calibration curve - 1. any hard to reproduce procedure that's the same for both the unknown and IS shouldn't influence the determination 2. It's possible to use a single IS for several unknown GC peaks as long as specific RF values between IS and each sample component are known Solve for N when a GC peak has a retention time (tr) of 2.6 minutes and half width (w1/2) of 5 sec - N = 5402.592 Is a higher N more or less efficient? - Higher N = more efficient because it creates a more narrow peak Why is a narrow peak in a GC desirable? - Narrow peaks imply less spreading of analyte, a higher number of theoretical plates, and more efficient output which leads to the achievement of GOOD SAMPLE SEPARATION Block diagram of AAS instrument - light source -- Sample cell -- Monochromator -- Photodetector -- Readout What is the purpose of the flame in AAS? - -evaporates the solvent -atomizes the sample so the individual components can be analyzed What type of sample is AAS used to analyze? - samples requiring high sensitivity due to very small levels of analyte with a specific absorption line width, and for trace metals What quantities are plotted on x and y axis to create a straight line calibration curve in AAS? - x axis - concentration of analyte in ppm y axis - absorbance