[neon flash!]

these questions are from a course i study called "spectroscopy and bonding"
would appreciate help with the following questions.
i know showing owrking is forum policy, hence on ones that dont show any its because i have absolutely no clue.

Q1) what are the units for moment of inertia.
i know its I = ur2
u is in kg/molecule and r is in metres, so what would that make the units of I? kg/molecule metres.... :/ ?

Q2) when calculating bond lengths using eqn B = h/8pi^2 c your^2
why does the r value come out it metres?
because the units of B are cm-1 and c is in cm

Q3) Explain the concept of selection rules

Q4) describe the phenomenon of tunnelling in Quantum mechanic
a: tunnellling arised due to no-zero wavefuntions in forbidden regions and is the penetration of a particle into or through classically forbidded areas.
- i need more than this coz its a 10mark question

Q5a) In the microwave emission spectrum of H127I a transition from the J=2 to the J=1 state is observed at 26.24 cm–1. Calculate the rotational constant of H127I.   
is B just 1/2 x 26.5?

b) Given that the selection rule for pure rotational transitions is Δ J = –1, describe qualitatively the likely appearance of the microwave emission spectrum of a molecule such as H127I (at room temperature). Variations across the spectrum, if any, in intensities of absorption and in line spacings should be noted. You may wish to include a diagram in your answer.

c) Why is the selection rule Δ J = +1 not appropriate for a pure rotational emission spectrum?

Q6) Explain, briefly, which features of the infrared spectrum of a diatomic molecule may be   predicted from the rotational constant.

Q7) Describe and explain, briefly, the effects of anharmonicity on the structure of a single vibration-rotation infrared absorption band (for example the fundamental band).

q8) Explain how the particle in a box model can be used to estimate the electronic energies of the delocalised electrons in a conjugated organic molecule.

q9) Discuss how the particle in a box model helps us understand how the colour of a dye molecule can be varied by varying the length of the conjugated chain

q10) The intensity of v=0 → v=6 overtone transition is observed to be very much weaker than that of the fundamental transition. Explain why this is so.

q11) What are the values of the rotational angular momentum quantum number J for the rotational energy levels of the 7LiH molecule which are 5-fold and 7-fold degenerate respectively?

hope someone can offer some help with any of them

[CaverKat]

3) http://en.wikipedia.org/wiki/Laporte_rule should help
The length of the conjugated chain is analogous to the box (+ 1 bond length either side).  The delocalised e^- are confined to the box.
9) You have the length of the box and the number of pi electrons.  So you can work out the energy of the first transition, which may or may not correspond to absorption in the visible region of the electromagnetic spectrum.  If it's coloured, then you can roughly work out the wavelength --> wavenumber (i.e. frequency) --> etc. etc. and it should correspond to the wavefunction based on the box.  Sorry.  Really horrific explanation.
10) C'mon, you can't even make a guess??  First, what is an overtone transition?  Energy?  Probability?

[neon flash!]

thx.

q10) is it because its a bigger trainsition? first overtone is 0-1 level, 0-6 would require MORE energy surely?

q9) yeah i just forgot the eqn but i found it now wavenumber = 1/lambda

[CaverKat]

10) If it required more energy, would that result in a change in the intensity of the absorption or the wavenumber of the absorption?

Tricky question.  I always disliked the "Explain why this is so" type question.  So vague.