Physical Chemistry: Quantum Mechanics – Exam I Material – Flashcards
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Define statistical thermodynamics.
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Statistical thermodynamics ties classical thermodynamics to what is known about molecules, through averages over many different molecules.
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Define correspondence principle.
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The correspondence principle is the idea that as object get larger and larger, quantum mechanics must turn into classical mechanics.
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True or False: Quantum mechanics is an empirical theory.
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True
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What are the two failures of classical thermodynamics?
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1. Black body radiation 2. The photoelectric effect
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What is a black body?
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A black body is an object that doesn't reflect light, but can give off light. It both emits and absorbs electromagnetic radiation at all frequencies.
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What is black body radiation?
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"Black body radiation is a type of electromagnetic radiation within or surrounding a body in thermodynamic equilibrium held at a constant, uniform temperature."
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Define energy density (energy per unit volume).
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Energy density is the amount of energy stored in a given system per unit volume or mass. Energy per unit volume has the same physical units as pressure.
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Define emittance.
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Emittance is the power emitted per unit area of the black body; sometimes referred to as 'brightness.'
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What is the equation for emittance?
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M=σT^4
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What is σ in the equation for emittance?
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σ is the Stefan-Boltzmann constant; units can be converted from W•m^-2•K^-4 into J•s^-1•m^-2•K^-4.
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What is the Wein Displacement Law?
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The Wein Displacement Law states that the maximum intensity of a black body shifts to shorter wavelengths as temperature is increased; given by the equation T•λmax= (1/5)C2.
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What is the second radiation constant?
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C2= 1.439 cm•K
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Explain the logic behind the Wein Displacement Law.
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The maximum intensity of a black body shifts to shorter wavelengths as temperature increases because at higher temperatures, high-energy oscillators that could not previously acquire necessary energy to oscillate can now do so.
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What is Rayleigh-Jeans Law?
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ρ(v,T)dv= ((8πv^2)/c^2)KTdv
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What is the ultraviolet catastrophe?
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The ultraviolet catastrophe is the failure of Rayleigh-Jeans Law at high frequencies (short wavelengths).
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What is represented by the following two equations? ρ(v,T)dv=((8πhv^2)/c^2)(1/(e^(hv/KT))-1)dv ρ(λ,T)dλ=((8πhc)/λ^5)(1/(e^(hc/KTλ))-1)dλ
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Plank's Radiation Law
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Define quantization of energy.
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For energy to be quantized means that only certain energies are allowed.
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Define a photon.
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A photon is a 'packet' of light with mass, energy and momentum.
