CHEM344 HW#6 Due: Fri, Mar [email protected] BEFORE CLASS! HW to be handed in: Atkins Chapter 7: Exercises: 7.11(b), 7.12(b), 7.13(b), Problems: 7.4, Chapter 8: Exercises: 8.6(b), 8.8(b), 8.19(b), Problems: 8.10, 8.14(a only), 8.32, Extra (do not hand in): Chapter 7: Problems: 7.8, Chapter 8: Exercises: 8.1(b), 8.3(b), 8.4(b), 8.7(b), 8.18(b), Problems: 8.28, 1. [7.11(b)] An unnormalized wavefunction for an electron in a carbon nanotube of length L is sin(2πx/L). Normalize this wavefunction. 2. [7.12(b)] For the system described in Exercise 7.11b, what is the probability of finding the electron in the range dx at x = L/2? 3. [7.13(b)] For the system described in Exercise 7.11b, what is the probability of finding the electron between x = L/4 and x = L/2? 4. [7.4] The ground-state wavefunction for a particle confined to a one-dimensional ⁄ box of length L is ( ) ( ) Suppose the box is 10.0 nm long. Calculate the probability that the particle is (a) between x = 4.95 nm and 5.05 nm, (b) between x = 1.95 nm and 2.05 nm, (c) between x = 9.90 nm and 10.00 nm, (d) in the right half of the box, (e) in the central third of the box. 5. [8.6(b)] What are the most likely locations of a particle in a box of length L in the state n = 5? 6. [8.8(b)] A nitrogen molecule is confined in a cubic box of volume 1.00 m3. Assuming that the molecule has an energy equal to 3/2kT at T = 300 K, what is the value of n = (nx2 + ny2 + nz2)1/2 for this molecule? What is the energy separation between the levels n and n + 1? What is its de Broglie wavelength? Note: this sort of glosses over the 3-D aspect of the box, but you could have gotten same answer for nx by solving for Ex=½kT 7. [8.19(b)] Calculate the value of |ml | for the system described in the preceding exercise corresponding to a rotational energy equal to the classical average energy at 25°C (which is equal to 1/2kT). Note: from 8.19(a) the system is a proton constrained to rotate in a circle of radius 100 pm around a fixed point. Note: moved to Problem Set #7 8. [8.10] The wavefunction inside a long barrier of height V is ψ = Ne−κ x. Calculate (a) the probability that the particle is inside the barrier and (b) the average penetration depth of the particle into the barrier. 9. [8.14 (a) only] Determine the values of Δx = (<x2> − <x>2)1/2 and Δp = (<p2> − <p>2)1/2 for (a) a particle in a box of length L and (b) a harmonic oscillator. Discuss these quantities with reference to the uncertainty principle. 10. [8.32] Many biological electron transfer reactions, such as those associated with biological energy conversion, may be visualized as arising from electron tunnelling between protein-bound co-factors, such as cytochromes, quinones, flavins, and chlorophylls. This tunnelling occurs over distances that are often greater than 1.0 nm, with sections of protein separating electron donor from acceptor. For a specific combination of donor and acceptor, the rate of electron tunnelling is proportional to the transmission probability, withκ ≈ 7 nm−1 (eqn 8.19). By what factor does the rate of electron tunneling between two co-factors increase as the distance between them changes from 2.0 nm to 1.0 nm? Extra (do not hand in): 11. [7.8] The normalized wavefunctions for a particle confined to move on a circle are ψ(φ) = (1/2π)1/2e−imφ, where m = 0, ±1, ±2, ±3, . . . and 0 ≤ φ ≤ 2π. Determine <φ>. 12. [8.1(b)] Calculate the energy separations in joules, kilojoules per mole, electronvolts, and reciprocal centimetres between the levels (a) n = 3 and n = 1, (b) n = 7 and n = 6 of an electron in a box of length 1.50 nm. 13. [8.3(b)] Calculate the expectation values of p and p2 for a particle in the state n = 2 in a square-well potential. 14. [8.4(b)] Calculate the expectation values of x and x2 for a particle in the state n = 2 in a square-well potential. 15. [8.7(b)] Calculate the percentage change in a given energy level of a particle in a cubic box when the length of the edge of the cube is decreased by 10 percent in each direction. 16. [8.18(b)] Confirm that wavefunctions for a particle in a ring with different values of the quantum number ml are mutually orthogonal. 17. [8.28] Starting from the operator ̂ = xpy − ypx, prove that in spherical polar coordinates ̂ = −i ∂/∂φ.

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