from pqs

Question 1

SPACING between 2 peaks in rotational spec =

Answer 1

2B!!!

Question 2

the first transition being at 3.84cm-1 : how do we find B etc

Answer 2

first transition = 0 –> 1

so 2B (J+1) is used
2B (0+1) = 2B,, so the first peak is at 2B!!

smallest J value is used

Question 3

units for inertia

Answer 3

kgm^2

Question 4

in rotvib spec they can ask u how to find the rotational constant, B and bond lengths ,, how do u do this

Answer 4

rememeber that in rot vib. the gap between every peak is 2B.

rot vib = 2 vibrational specs,, one for v=0 and one for v=1. so each peak gap = 2B.

then find the gap in cm-1 and divide by 2 to find B. then do the rest t find I, reduced mass and bond length.

Question 5

in rot vib, when they ask u to estimate ‘k’ force constant,, what should u do

Answer 5

look in the rot vib spec and look at here the bond origin is.

this is the large gap. this is Wo but we can say its similar to We. so u just piut this into the equation for force constant.

u put c in cm!!! 10^10.

Question 6

units for I intertia

Answer 6

Kgm^2

bc inertia is bond length^2 and reduced mass which is in KG

Question 7

units for bond length in inertia

Answer 7

m

Question 8

units of force constant

Answer 8

Nm-1 !!

Question 9

how to find v max

Answer 9

vmax = (1/2xe)-1

this gives u the max energy level!!!!!

then use the equation to find the energy of this energy level (anharmonic version)

and this will be ur dissociation energy

Question 10

cm-1 to J –> kjmol-1

Answer 10

cm-1 x h x c (10^10) = J

J x avo // 1000 = kjmol-1

Question 11

how to find the dissociation energy

Answer 11

find v max (highest vibrational energy level )

using (1/ 2 Xe) -1

then find the energy of this Vlevel. and thats ur answer!!

Question 12

if we’re given we and wexe how do we find xe

Answer 12

wexe / we = xe

should be a smallish number

Question 13

what should be larger in energy and why.

Do’ or Do’’

Answer 13

Do’’ = dissociation eneergy of ground state should be higher in energy

bc its more stable so it requires more energy to break that bond

Question 14

excitation energy =

Answer 14

Eex

the difference between the 2 plateaus!!

Question 15

rot spec only

Answer 15

perm dipole

heteronuclear diatomics
no planar or tetrahedral stuff

Question 16

rot vib spec

Answer 16

change dipole and perm dipole

heteronuc diatomics
planar and tetrahedral stuff aswell. when u stretch a bond a dipole will be created

Question 17

when in rot spec they ask u for the wavenumber of the transition!!! make sure u use the right equation. they dont want energy of that level,, they want energy of the transitionnnnn

Question 18

steps for finding xe and we

Answer 18

find the wavenumbers for the things given : eg the first fundamental transition and first overtone and fine the equations.

expand the brackets for each one.
MULTIPLY each one by a factor that will make both have the same wexe value. then solve like a simultaneous equation

find what one we is.

then sub it back in to find XEWE

then divide this value by we to find xe.

then u have both of them yay ,, youve got this girl!!!