Etude is a French word, meaning study.
A short composition for a solo instrument intended
as an exercise or to demonstrate technical virtuosity.
Only once, and in the right hand in measure 66, is a white key played in Frederic Chopin's Etude for Piano in G-flat Major, Opus 10, No. 5, called appropriately--and what else!--the Black Key Etude. The left hand plays the melody, mostly chords and octaves,while the right hand accompanies with the fast triplets on black keys.
A short composition for a solo instrument intended
as an exercise or to demonstrate technical virtuosity.
Only once, and in the right hand in measure 66, is a white key played in Frederic Chopin's Etude for Piano in G-flat Major, Opus 10, No. 5, called appropriately--and what else!--the Black Key Etude. The left hand plays the melody, mostly chords and octaves,while the right hand accompanies with the fast triplets on black keys.

Excerpts from the Black Key Etude