Concept explainers
(a) Using the he expression for the energy of a 3-D rigid rotor, construct the expression for the energy difference between two adjacent levels,
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Physical Chemistry
- Estimate the lifetime of a state that gives rise to a line of width (i) 200 MHz, (ii) 2.45 cm−1.arrow_forwardAssume that for ¹H35 Cl molecule the rotational quantum number J is 11 and vibrational quantum number n = 0. The isotopic mass of ¹H atom is 1.0078 amu and the isotopic mass of 35 C1 atom is 34.9688 amu, k = 516 N · m¯¹, and x = 127.5 pm. Part E Calculate the period for vibration. Express your answer in seconds to three significant figures. Tvibrational = Part F Submit Previous Answers 1.12x10-14 s Correct Correct answer is shown. Your answer 1.1181.10-¹4 = 1.1181x10-14s was either rounded differently or used a different number of significant figures than required for this part. Calculate the period for rotation. Express your answer in seconds to four significant figures. Trotational = ΑΣΦ W ? Sarrow_forwardCalculate the linear momentum of photons of wavelength (a) 600 nm. (b) 70 pm. (c) 200 m.arrow_forward
- A swimmer enters a gloomier world (in one sense) on diving to greater depths. Given that the mean molar absorption coefficient of sea water in the visible region is 6.2 × 10−5 dm3 mol−1 cm−1, calculate the depth at which a diver will experience (i) half the surface intensity of light, (ii) one tenth the surface intensity. Take the absorber concentration to be 10 mmol dm−3.arrow_forwardCalculate the value of ml for a proton constrained to rotate in a circle of radius 100 pm around a fixed point given that the rotational energy is equal to the classical average energy at 25 degrees C. (Mass of a proton = 1.6726 x 10^-27 kg, classical average energy=1/2kBT, where kBT is Boltzman constant = 1.30 x 10^ -23 J K^-1, and T is the temperature.)arrow_forward(b) Calculate the half width in nanometers for Doppler broadening of the 4s S 4p transition for atomic nickel at 361.939 nm (3619.39 Å) at a temperature of 20,000 K in both wavelength and frequency units. (c) Estimate the natural line width for the transition in (b) assuming that the lifetime of the excited state is 5*10^(-8) s.arrow_forward
- The molar absorption coefficient of a solute at 540 nm is 386 dm3 mol−1 cm−1. When light of that wavelength passes through a 5.00 mm cell containing a solution of the solute, 38.5 per cent of the light was absorbed. What is the molar concentration of the solute?arrow_forwardCalculate the energies of the first four rotational levels of 1H127I free to rotate in three dimensions; use for its moment of inertia I = μR2, with μ = mHmI/(mH + mI) and R = 160 pm. Use integer relative atomic masses for this estimate.arrow_forwardWhen ultraviolet radiation of wavelength 400 nm passes through 2.50 mm of a solution of an absorbing substance at a concentration 0.717 mmol dm−3, the transmission is 61.5 per cent. Calculate the molar absorption coefficient of the solute at this wavelength. Express your answer in square centimetres per mole (cm2 mol−1).arrow_forward
- (b) A system with chemical potential u = 12.5 meV contains identical particles each with integer spin and has a single quantum state at energy E, = 0 meV. The temperature of the system is fixed at 290 K. To three significant figures, what is the ratio Pg/P1, where P is the probability of finding a single particle in the state Eo, and P3 is the probability of finding 3 particles in this state? P3/P (Input your answer as a number.)arrow_forwardAssume that the states of the π electrons of a conjugated molecule can be approximated by the wavefunctions of a particle in a one-dimensional box, and that the magnitude of the dipole moment can be related to the displacement along this length by μ = −ex. Show that the transition probability for the transition n = 1 → n = 2 is non-zero, whereas that for n = 1 → n = 3 is zero. Hints: The following relation will be useful: sin x sin y = 1/2cos(x − y) − 1/2cos(x + y). Relevant integrals are given in the Resource section.arrow_forward(a) Calculate the moment of inertia of (i) 1H2, (ii) 2H2, (iii) 12C16O2, (iv) 13CO2 . (b) Calculate the corresponding rotational constants, expressing your answers as a frequency in hertz (Hz) and as a wavenumber in reciprocal centimetres (cm-1).arrow_forward
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