{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

Fall 09. Exam3 key

Fall 09. Exam3 key - CHEMISTRY 2101 Fall 2009 Dr Philippe...

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

View Full Document Right Arrow Icon
CHEMISTRY 2101 Name___________________________ Fall 2009 Dr. Philippe Buhlmann Hour Exam III December 7, 2009 Page 2 (1) (30 points in total) Spectroscopy (a) (5 points) Which wavelengths are larger, the ones at which a molecule absorbs light or the ones at which a molecule fluoresces? Explain your answer. Fluorescence occurs at longer wavelengths than absorption. Absorption typically excites a molecule from the lowest vibronic level of the electronic ground state into an electronically and rotationally excited state. Relaxation into the (electronically still excited) vibronic ground state is fast and represents a loss in energy that later is missing when fluorescence occurs. Fluorescence occurs by transition from the vibronic ground state/electronically excited state into different vibronic levels of the ground state. (b) (5 points) The slit in a UV/Vis spectrophotometer: What are the advantages and disadvantages of a large slit width? Advantage: Sensitive measurement due to large amount of light (large photon flux) reaching the detector. Disadvantage: Results in low resolution. (c) (5 points) What is the solvatochromic effect? What is the reason for the solvatochromic effect? Solvatochromic effect: The absorbance spectrum depends on the solvent. The solvatochromic effects results from a different extent of solvation of the electronic ground state and the electronically excited state(s). {Stronger solvation of the electronically excited state results in a shift to larger wavelengths, and stronger solvation of the electronic ground state results in a shift to shorter wavelengths.}
Image of page 1

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

View Full Document Right Arrow Icon
CHEMISTRY 2101 Name___________________________ Fall 2009 Dr. Philippe Buhlmann Hour Exam III December 7, 2009 Page 3 (d) (5 points) Why does a typical UV/Vis spectrophotometer have two different types of light sources? What are those two light sources? Explain in your answer the role of each light source.
Image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the 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