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Homework 21 (6/1/2016)

  • Page ID
    47407
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    Section: _____________________________

    Student ID#:__________________________

    Q21.1

    What is the wavenumber and frequency of a 450-nm photon? How does the energy of 450-nm light compare to the energy used to overcome activation barriers in chemical reactions (i.e., thermal energy \(k_bT\)) at room temperature?

    Q21.2

    Convert the following absorbance of a sample to percent transmittance: (a) 0.0, (b) 0.12, and (c) 0%.

    Q21.3

    An excited molecule has an average lifetime of \(2.0 \times 10^{-8} \ seconds\), and the radiation emission is 600 nm. Find the frequency and wavelength uncertainties.

    Q21.4

    What is the concentration of a lysozyme solution if a 1.0-cm wide cuvette containing the solution transmits 25% of λ = 280 nm (UV) light? The molar extinction coefficient for lysozyme at 280 nm is 26.4 L mol-1cm-1.

    Q21.5

    The Doppler effect results in a shift in the wavelength of a star in astronomic meaurements, but only to a broadening of a transition in a gas; why?

    Q21.6

    Which of these transitions are possible for the electronic absorption of an atom or molecule?

    1. A 1s electron in hydrogen is promoted to the 2p orbital
    2. A 1s electron in hydrogen is promoted to the 3d orbital
    3. A 2s electron in hydrogen is promoted to the 3d orbital
    4. An electron with the quantum numbers (\(n=2\), \(l=1\), \(m_l=1\) and \(m_s=+1/2\) in hydrogen is demoted (e.g., via the emission of a photon) to a wavefucntion with the quantum numbers (\(n=1\), \(l=0\), \(m_l=0\) and \(m_s=+1/2\).
    5. An electron with the quantum numbers (\(n=2\), \(l=1\), \(m_l=1\) and \(m_s=+1/2\) in hydrogen is demoted (e.g., via the emission of a photon) to a wavefucntion with the quantum numbers (\(n=1\), \(l=0\), \(m_l=0\) and \(m_s=+1/2\).

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