Page 1 of 1

2011 Q1C heat capacity, residual entropy

Posted: Thu Mar 12, 2015 4:52 pm
by 204301116
Can someone please explain these to me?
Thank you

Re: 2011 Q1C

Posted: Thu Mar 12, 2015 5:40 pm
by Niharika Reddy 1D
Heat capacity increases with molecular complexity. As more atoms are present in a molecule, there are more possible bond vibrations that can absorb added energy. In addition to having more atoms, ethane has a C-C single bond, which allows it to have rotational freedom, whereas ethene has a C-C double bond that makes it more rigid since double bonds don't allow rotation.

NO has 2 distinguishable microstates (NO and ON) whereas BF3 is indistinguishable when the fluorine atoms exchange places. Residual entropy indicates using S=kblnW, and the degeneracy (W) will be greater for NO than BF3, so the residual entropy of NO will be greater as well.