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Chem 105A Experimental Descriptions

GROUP A – THERMODYNAMICS

A1 – PMV volume is different from the one that is there?

A2 – RUBBER BAND experiment. Most popular.

A3 – BOMB CALORIMETRY. Energy release, temperature rise in a big bath. Looking for the resonance energy of benzene. Simple measurement of a rise in temp. Measuring deltaT for bath. Macroscopic measurement, going to determine a purely quantum mechanical concept. Take the sum of three single bond energies and energies of 3 double bonds, taking into account of 3Hs, will not account for what is expected of benzene. This is because of resonance (a quantum thing: wave functions, locations, MO diagrams (bonding structure of benzene), state functions, constant volume heat capacities, Hess law to couple with MO diagrams).

 

GROUP B – PURE QUANTUM MECHANICS
like Chem 133.

B1 – IR spectra of a gas (N20 laughing gas). Measuring Ro-vibrational spectrum (rotational + vibrational simultaneously). Harmonic well, rotation levels are buried inside. Can go to any vibrational levels.

Types of information: bond length coupled to computation (is N20 a greenhouse gas and how does it compare to CO2). Greenhouse gases are stable and stay in atmosphere for a long time. Leads to ozone depletion & climate change (global warming). Greenhouse means it readmits radiation from Earth–cannot release it. What about the molecule will determine whether it is a greenhouse gas? (Answer: infrared absorption efficacy). This is a computational chemistry experiment.

 

B2: DISSOCIATION of I2 to FOCUS ON HIGHER ENERGY TRANSITIONS – visible electronic transition (harmonic potential wells with vibrational wells, but instead of transition within a single electronic state to a higher electronic state). What is the principle of why it is a vertical transition of reorganization and wave functions. Bottom line: simple experiment done in 2 hours. Take data to determine distance of one atom from other identical atom.

 

GROUP C – KINETICS & REACTIVITY

C1: HYDROLYSIS of METHYL ACETATE – simple organic reaction. Physical organic chemistry. Measuring forward and backward rates, as a function of temperature. Rate constant or rates as a fxn of temperature is Arrhenius behavior model. What do you get out of it? Collisional pre-factor. Arrhenius is a physical chemistry view of Activation Energy (Ea), showing how to get from reactant to product, but on the top is the transition state. The energy associated with transition state. A lot of titrations.

C2: BROMINATION of ACETONE – somewhat complex. Must be organized with 16 samples measured. Acid-catalyzed bromination reaction. Measuring the rate at which bromination reaction is proceeding. The rate is measured using spectroscopy. Goal is to determine the rate law. What precedes rate law? I wanna know how mechanism occurred. Predict the rate law based on mechanism. How mechanism translates to rate law. Stoichiometry has nothing to do with rate law. Order only depends on mechanism.

C3: EMISSION SPECTROSCOPY – photophysical process. Not getting a single answer. Not activation or resonance energy. More qualitative. No single number, but concepts are photophysics, molecular interactions, fluorescence (re-emission of a photon after it excitation–when drops from an excited state to ground state). Fluorescence is given off into solvent as heat or extra energy given as a form of another photon, but this not necessarily 100%. Organic molecule (molecule orbital). Focus on the relationship between absorption and fluorescence. If molecule absorbs a certain wavelength, then it will tell you something about typically different photon. Jablonsky diagram in detail.

C4:  BIOPHYSICAL EXPERIMENT – related to C3. Only experiment with cytochrome c – protein. A heme protein. Experiment based on Forster resonance energy transfer (FRET).

D1:  VISCOSITY OF POLYMER (ENGINEERING)

D2:  FUNDAMENTAL CONSTANTS

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