URGENT please! Chem questions

Shouldn't the eigenvector be a column vector? Otherwise, this looks fine.

Right...But in the other cases like angle BAC, do I still need to find BA and CA?

Yes, you want BA and CA (or AB and AC). What you had was BA and AC.

Yes, you want BA and CA (or AB and AC). What you had was BA and AC.

Sorry for bothering you again, but maybe you also know how to solve this type of question:
A system consisting of eight molecules possesses four quanta of energy. How many different configurations may the system occupy?
I was thinking that it's basically multiplication of molecule by quanta that must equal to the total number of quanta (4 in this case). Please correct me if I'm wrong

Yes it's just simply a case of listing the possibilities, I think you had it in the other thread but if you need further explanation I'll try to help!

I think the easiest approach is to simply list all the possibilities. The alternative is some not-very-pleasant maths, as far as I can tell — you're asking about partitions, which are not something I know anything about. Maybe somebody in the maths forum can give you a better answer.

May I ask you one last question, I promise? :P
The molar heat capacity of CH2Cl2 over the range 230 K to 310 K is given by Cp,m/J K-1mol-1= 91.5 + 0.0751(T/K)
Given that the change in the molar entropy on heating is ΔS= ∫ Cp,m / T dT
calculate the change in the entropy when 0.200 mol of CH2Cl2 is heated from 5°C to 30°C.

I have the answer to it ( 1.951J K-1 mol-1) but can't get it right for some reason. My working:
ΔS= Cp,m ∫ 1/T dT = Cp,m * ln(303K/278K) ...Any help is appreciated