finala - CHEM 209 Final Exam NAME 1(30 POINTS(a A Chemistry...

Info icon This preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: CHEM 209 Final Exam 10/3/05 NAME: 1. (30 POINTS) (a) A Chemistry major obtains a high-paying summer job in an _ analytical laboratory and is given the task of determining the ethanol content (in vol %) of a commercial mouthwash sample. He/she decides to do this by gas chromatography because the experiment was so enjoyable in Chem 209. Accordingly, the student takes exactly 2.0 mL of the mouthwash sample and dilutes this to 25.0 mL with deionized water. Hefshe then injects 2.0 pL of the diluted sample into the GC and obtains a chromatogram containing two peaks. The first peak, which corresponds to ethanol, has a retention time of 75 seconds and an area of 216 while the second peak, which corresponds to water, has a retention time of 117 seconds and anarea of 1212. The student then makes up several standard ethanol solutions ranging from 0 to 30% ethanol (vol %), injects 2.0 pL of each into the GC, and uses the areas of the ethanol peak to create a calibration curve whose linear regression equation is: y= 144.2 x Calculate the ethanol concentration (vol %) of the mouthwash sample. SHOW ALL _ WORK. (b) Suppose that chromatograrn obtained for an unknown'sample contains six distinct peaks. _ What is the minimum number of different species in the sample? What is the maximum number of different species in the sample? Briefly indicate two reasons why these two numbers might not be the same. __...__.___..—.~——__.... _W mm ——___._..._..—.-———.—.._...t.... 2. (10 POINTS) Write the equilibrium constant expressions for the following chemical reactions: -(a) H80; + 13‘ + 3H20 -—--> HSO4‘ +3I' + 2H30+ K: (b) Ag + cr --——+ AgCle (solid) K: 3. (30 POINTS) (3) Write the balanced chemical reaction that occurs during the complete titration of Na2C03 with HCl. (b) On the graph below, sketch the shape of the titration curve expected for this titration. mL H01 (c) If the NaZCOs weight taken for the titration was 0.3333 gram and concentration of the HCl solution was 0.096M, calculate the equivalence point volume expected. SHOW ALL WORK CLEARLY. (Formula weights: Na2C03 = 105.99 g/mole; HC1= 36.46 g/mole) 4. (20 POINTS) Draw block diagrams of each of the following analytical instruments, labeling all the important components. (a) a gas chromatograph (GC) (b) a visible spectrophotometer (e.g., the Spectronic 20) 5. (10 POINTS) Calculate the following and SHOW YOUR WORK: (3) the pH of a 0.025M NaOH solution. (b) the %T of a solution whose absorbance is 0.90. "iwmkhmmw—u——u..__..._.._._..‘......_._..‘.....» m - ...
View Full Document

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern