Consider a molecule having three energy levels as follows:

State Energy (cm−1) Degeneracy
1 0 1
2 500 3
3 1500 5
Imagine a collection of N molecules all at 260. K in which one of these molecules is selected. Note: k=0.69503476cm−1⋅K−1.

1) What is the probability that this molecule will be in the lowest-energy state?2) What is the probability that it will be in the highest-energy level?

Respuesta :

Answer:

1) Probability that the molecule will be at the lowest energy state = 0.843

2) Probability that it will be the highest energy level = 0.000986

Explanation:

[tex]E = hc \bar{v}[/tex]

[tex]h = 6.67 * 10^{-34} \\c = 3 * 10^{8} \\hc = 2.001 * 10^{-25}[/tex]

The lowest energy is at [tex]\bar{v} = 0[/tex]

[tex]E_{1} = 2.001 * 10^{-25} * 0[/tex]

[tex]E_{1} = 0 J[/tex]

At [tex]\bar{v} = 500 * 10^{2} m^{-1}[/tex]

[tex]E_{2} = 2.001 * 10^{-25} * 500 * 10^{2}[/tex]

[tex]E_{2} = 1 * 10^{-20} J[/tex]

At [tex]\bar{v} = 1500 * 10^{2} m^{-1}[/tex]

[tex]E_{3} = 2.001 * 10^{-25} * 1500 * 10^{2}[/tex]

[tex]E_{3} = 3 * 10^{-20} J[/tex]

If the degeneracy of a system is g and the energy is E, the probability of the system is :

[tex]P(E) = \frac{ge^{\frac{-E}{kt} } }{\sum ge^{\frac{-E}{kt} } }[/tex]

Boltzmann constant, k = 1.380649×10−23 J/K.

Absolute temperature, T = 260 K

kT =  1.380649×10⁻²³ * 260

kT = 3.59 * 10⁻²¹

Probability that the molecule will be at the lowest energy state

Degeneracy g₁ = 0, g₂ = 3, g₃ = 5

[tex]P(E_{1} ) = \frac{1*e^{\frac{0}{kt} } }{ 1*e^{\frac{0}{kt} }+3*e^{\frac{-10^{-20} }{3.59*10^{-21} } }+5*e^{\frac{-3*10^{-20} }{3.59*10^{-21} } } }[/tex]

[tex]P(E_{1} ) = \frac{1}{1 + 0.185 + 0.00117}[/tex]

[tex]P(E_{1} ) =0.843[/tex]

2) Probability that it will be the highest energy level

[tex]P(E_{2} ) = \frac{5*e^{\frac{-3*10^{-20}}{3.59*10^{-21}} } }{ 1*e^{\frac{0}{kt} }+3*e^{\frac{-10^{-20} }{3.59*10^{-21} } }+5*e^{\frac{-3*10^{-20} }{3.59*10^{-21} } } }[/tex]

[tex]P(E_{2} ) = \frac{0.00117}{1+0.185+0.00117}[/tex]

[tex]P(E_{2} ) = 0.000986[/tex]