This piece is hard to analyse because of its tonality and the blending and transition of sections. Also, Chopin really seems to avoid periods and classical phrases, preferring rather the more organic and melodically adventurous tread of the Romantics.
As an example of Ternary form, I'd have to say the A section (m1-m44) is open because it begins in the key of Ab major only to modulate to the related key of c minor. You can divide it into two parallel phrase groups (the second beginning in measure 22). Each begins with the c moving up to the d, but the first phrase group is four measures (with a sort of plagal feel), the second is 5 measures (IAC), the third is four (another plagal feel), and the fourth is ten and takes place in the key of c minor, ending with an embellished broken IAC which transitions first back to the repetition of the phrase group at m.22 and then into the B section.
The B section is in f minor with four similar phrase groups (each beginning with the f and its grace note). You don't really get an authentic sense of cadence (no pun intended) until measure sixty where the soprano leads up ti to do and the bass ends on C. Each of these phrase groups are four measures. Then after that authentic conclusion, we return to the original A theme but for its first appearance, it can't seem to decide between fm or Ab and is markedly different from the original exposition--but you can still catch the beginning C motif. At measure 77, it seems as though it might stay in the original Ab, but it immediately begins a spiraling journey through key and texture, only to calm once more at measure 88 and transition finally with a descending line back into the original Ab by m 108 and concludes with two bars of pianissimo termanitive tonic.
The Chapter didn't give many names or distinctions by which to label ternary. There is A, then a constrasting B, and here a modified A--but it does end in the original key of A. A is open. The melody likes to run like a nose in the cold through and over classical period sense (gotta love the phrase groups), and Chopin tends to avoid cadences.