Mozart's Piano Sonata in D Major has a very confused and probably incorrect chordal analysis that is :
m.25: I I64
m. 26: vii/ii ii vii7/ii vii I
m. 27: vii7 I V65/IV
m.28: iv I iv
Mozart sets up a feeling of a pattern in measures 26 and the beginning of 27 with the use of a vii and a ii. The listener then expects this type of chordal structure to continue. At this point Mozart throws in the use of iv because it changes the mood of the line. As the line seemed to be pushing along with the earlier pattern, the iv allows the line to change direction and come to a conclusion. The modal mixture helps transition the faster beginning into the contrasting slower and lower next few bars. There are not as many obvious reasons for this choice of a mode mixture chord because there are no text indications.