CHEM 120A Study Guide - Midterm Guide: Problem Set, Standard Deviation, Virial Theorem

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8 Jan 2019

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Scoring: 7x 3. 5y, where x are the number of correct answers and y are the number of incorrect answers. Note that negative scores were treated as 0. (b) answer: ii and v. Notice that multiplying a wave function by i does not change the wave function. Scoring: 7x 4y (c) answer: ii, iv, and vi remember that for any operator we have, dh gi dt. This equation was given to you at the beginning of the exam. Of course, h commutes with itself and so its expectation value is time-independent. You can calculate the uncertainty in h which is k. Problem set 3 question 2. c) provides the nal answer. Scoring: 6x 6y (d) answer: iii, iv, v, and vii. |ai and |bi are orthonormal and the action of c on both states is given. Using this information you can show that iii and iv are true.

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The equilibrium A ? B is first-order in both directions. We will now do a step-by-step derivation of an expression for the concentration of A as a function of time. (i) Given the initial molar concentrations of A and B are [A]0 and [B]0 , derive an expression for d[A]/dt that includes only constants and the variable [A] (ii) Re-arrange this expression so it is of the form dy/dx + yf(x) = g(x) where f(x) and g(x) are constants. Derive an integrated expression for the concentration of A . (iv) Use the boundary condition that at time t = 0, the concentration of [A] = [A]0 in order to determine the constant of integration. (v) Write the simplified final expression for the concentration of A as a function of time. (vi) In order to be confident our answer is correct, determine the final composition of the system (ie, what is [A] as t ? ?)? Consider two limiting scenarios (a) Keq << 1 and (b) Keq >> 1 and show that final composition makes sense.

SEE ATTACHED IMAGE FOR A BETTER DESCRIPTION! Please answer all parts of the question in detail, I am very confused. Thank you!

Hi could you help me with this problem please?

The following spectroscopic data were obtained for an organic compound:
i. MS (relative abundance in parentheses): M⁺ = 86 ; signals at 29 (92) and 41 (100) among others
ii. IR (cm^-1): 3100 (weak sharp), 2970 (medium sharp), 2850 (medium), 1650 (weak sharp), 1100 (strong sharp)
iii. H¹ NMR :
Signal A at 4 ppm (3H, triplet),
Signal B at 3.53 ppm (2H quartet),
Signal C at 4.01 ppm (2H, doublet),
Signal D₁ at 5.25 ppm (1H, doublet)
Signal D₂ at 5.28 ppm (1H, doublet)
Signal E at 5.95 ppm (1H, multiplet)
note: signal D₁ and D₂ are two separate signals, right next to each other, each with integration of 1H and multiplicity of "doublet"
iv. C13 NMR (proton \-decoupled):
Signal I at 14 ppm,
Signal II at 64 ppm,
Signal III at 71 ppm,
Signal IV at 115 ppm
Signal V at 135 ppm.

Please answer the following:
A. Draw the most likely structure of this compound. Show all of the hydrogens in the structure.

B. Label all H's with the signal letter that the Hproduces in the H¹ NMR spectrum. Explain why each H¹ NMR signal has the chemical shift specified. Be specific about each group of chemically-equivalent protons in this particular compound (not in general)

C. Explain multiplicities for EACH and EVERY H¹ NMR signal (i.e. what is each signal being split by?). Make sure to explain why there are actually two signals near 5.25 ppm (signals D₁ and D₂) that are both doublets, instead of a single signal that would be a doublet of doublets. Note: The hydrogens producing signals D₁ and D₂ are actually coupled to each other, but the coupling constant is so small that it is hard to see any coupling of D₁ with D₂ in the spectrum. The info for D₁ and D₂ above assume that J for these two protons is 0 Hz. Also assume that long-range coupling is not observed.

Need help with #2

Electrochemistry. Please show work, label all answers clearly, and write legibly. Standard reduction potentials are found in Appendix E of your textbook On your paper, at the TOP, write (a) the FULL NAME of your TA; and (b) your section as "SECTION ##". Failure to do this will result in a deduction of I pt The following diagram, called a Latimer diagram, summarizes the standard reduction potentials for various nitrogen-containing compounds and ions in acidic aqueous solution. It contains useful data for this HW set. 0.97 V 0.79 V 1.12 V 1.00 V 1.59 V 1.25 V 0.89 V An arrow represents the "properly balanced reduction half-reaction" between the oxidized species on the left and the reduced species on the right of the arrow. The potential value over each arrow is the standard reduction potential E'ned for that properly balanced half-reaction. For example, from this diagram, you can write No, (aq) + e + 2 H+(aq)-â NO2(g) + H20(/); E0ted _ +0.79 V (1) (18 pts) When H S(g) is bubbled into nitric acid solutions, S(s), NOg), NO(g), N2(g), and NH4 (a) all form. (a) (8 pts) Write the four balanced reactions that describe this complex process. (b) (8 pts) For each reaction in part (a), calculate the standard emf (in V) (c) (2 pts) Which of the four reactions has the greatest driving force and which has the least driving force per electron (2) (16 pts) Use the Latimer diagram above for this question. (a) (6 pts) NO (g) disproportionates spontaneously into nitric acid and nitrous acid in acidic media. Show this (b) (6 pts) Nitrous acid will not disproportionate spontaneously to nitrogen dioxide and nitric oxide. Show this (c) (4 pts) Given that the definition of 1 volt = 1 Joule Coulomb, show that the reduction of the nitrate ion to by writing the balanced chemical reaction and evaluating the standard emf for the reaction. by writing the balanced chemical reaction and evaluating the standard emf for the reaction. nitrogen gas in acidic media has a standard reduction potential of +1.25 V (3) (6 pts) Active metals like zinc will react with concentrated nitric acid to produce the ammonium ion and the Zn (a) ion at 25Â°C (a) (4 pts) Write the balanced chemical equation for this process using smallest whole number coefficients. (b) (2 pts) Evaluate ÎEo (V) for the reaction in part (a). (4) (6 pts) Less active metals like copper will react with concentrated nitric acid to produce nitric oxide gas and the Cu (aq) ion at 25Â°C. (a) (4 pts) Write the balanced chemical equation for this process using smallest whole number coefficients. (b) (2 pts) Evaluate AE for the reaction in part (a). BONUS (8 pts; and PRACTICE): Write all balanced half-reactions indicated by the Latimer diagram above

CHEM 120A Study Guide - Midterm Guide: Problem Set, Standard Deviation, Virial Theorem

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