Read this and answer the question. If the question is unanswerable, say "unanswerable".

Some of Chopin's well-known pieces have acquired descriptive titles, such as the Revolutionary Étude (Op. 10, No. 12), and the Minute Waltz (Op. 64, No. 1). However, with the exception of his Funeral March, the composer never named an instrumental work beyond genre and number, leaving all potential extramusical associations to the listener; the names by which many of his pieces are known were invented by others. There is no evidence to suggest that the Revolutionary Étude was written with the failed Polish uprising against Russia in mind; it merely appeared at that time. The Funeral March, the third movement of his Sonata No. 2 (Op. 35), the one case where he did give a title, was written before the rest of the sonata, but no specific event or death is known to have inspired it.

How many instrumental works did Chopin give a descriptive name to?
one