Exam 3 key

Exam 3 key - Chem 10 Exam 3 Useful information: R = 0.08206...

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Chem 10 – Exam 3 Useful information: R = 0.08206 liter atm/ mol K = 8.3145 J/mol K h = 6.626 x 10 -34 J s, N A = 6.02 x 10 23 , mass of an electron = 9.11 x 10 -31 kg, mass of a proton = 1.673 x 10 -27 kg, 1 atm = 101325 Pa = 760 torr, F=95485 coul/mol, E = h ν = hc/ λ , c=3 x 10 8 m/s, E n = (n+1/2)h ν , ν = (1/2 π ) (k/ μ ) 1/2 , μ = m 1 m 2 /(m 1 +m 2 ) E J = h 2 /(8 π 2 I) J(J+1), I= μ R 2 , E n = n 2 h 2 /8mL 2 1. What is the energy (in kJ) of a mole of 500 nm photons? E = hc/ λ = 3.98 x 10 -19 J/photon = 2.39 x 10 5 J/mol = 239 kJ/mol 2. The infrared spectrum of CO has a peak at 2145 cm -1 . What is the force constant of the C-O bond? (Carbon has a mass of 12 amu and oxygen has a mass of 16 amu.) μ = 12 x 16/(12 + 16) = 6.86 amu = 1.14 x 10 -26 kg 1/ λ = 2145 cm -1 = 2.145 x 10 5 m -1 E = hc(1/ λ ) = h(2 π ) -1 (k/ μ ) 1/2 , solve for k. k = (2 π c 1/ λ ) 2 μ = 1864 N/m 3. Consider an electron in a 0.70 nm one-dimensional box. What wavelength of photon is needed to excite it from the n = 2 to the n = 3 level. Δ E = (3 2 – 2 2 ) h 2 /8mL 2 = 6.15 x 10 -19 J = hc/ λ λ = 3.23 x 10 -7 m = 323 nm 4. The infrared absorption for 14 N- 16 O is at 1876 cm -1 . Determine the wavenumber of the infrared absorption of the 14 N- 18 O molecule. (N has a mass of 14 amu. Take
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Exam 3 key - Chem 10 Exam 3 Useful information: R = 0.08206...

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