Clementi Analysis

Muzio Clementi, Sonatina in C Major, Op. 36, No.1, First Movement

This sonatina which every faithful piano student will suffer through some time or another when they first begin lessons looks something like this when analyzed:

m.1-8 : (C Major) I, V, I, V/V, V Half Cadence

m. 8-16 (G Major) V6, I, ii, I6, IV, V, I PAC... Contrasting Period

m. 16-23 (C Major) V42, i6, viid, i, V, V7, i64, viid, i, V HC

m. 24-end (C Major) I, V, I, V7, I V, I, V43, I6, IV, ii6, V7, I. PAC

So this piece follows Sonata form: m. 1-15 are the exposition, within the exposition the primary theme and first tonal area is in measures 1-8. The secondary theme and tonal area is in measures 8-15.
Measures 16-23 are part of the development. We know this because Clementi develops the themes from the exposition and places them within harmonies of different keys. It is rather harmonically unstable, using minor tonic harmonies and diminished seven chords. Measures 20-23 can be identified as the retransition. These measures lead to the HC in the original tonic key and prepare for the return of the primary theme.
Measures 24-end are part of the recapitulation, marked by the return of the themes from the exposition in the same order. The secondary theme is transposed to the tonic of the primary theme, and the transition material leads to the eventual PAC instead of modulating. I don't think there is a codetta, because the closing material uses themes from the exposition, no new theme is introduced and the listener doesn't really get a sense of closure until measure 38. In other words, it'd be really awkward to end anywhere else. Enjoy Clementisizing!