Where is the high F in 'Defying Gravity'?

Answer 1

The high F in 'Defying Gravity' is within the range of a standard alto, contralto, strong mezzo soprano, or soprano belter with a low range. Basically, Elphaba's vocal range is a little over 2 octaves. Each singer in the role of Elphaba brings her own range and her own singing voice [alto, contralto, mezzo soprano, etc.] to the part.

For a discussion of alto roles, such as that of Elphaba, in musical theatre, please visit the link provided below.

Answer 2

Last eighth note in the 179th measure tied to the first half note of the 180th measure of the full ensemble sheet music.

"Tell them how I am defying gravity. I'm flying high, deFY-ING gravity, and soon I'll match them in renown."

It's the high note on the FY in that second "deFY-ING" at nearly the very end of the whole song and Act 1.