Hi Ivan, I could be incorrect here but as far as I know, both ways the word "works" is written is correct. Using the singular form of "works", in the second example would not be the best way to write it.

Yes, usually "work" is an uncountable noun but when we say "a work", we mean "a work of art". So "the complete works of Dante" means everything that he created artistically. In the second sentence, "chemical works" means a chemical factory, like gasworks. If you write "chemical work", then you mean any possible work done using chemicals. The meaning changes. Where did you find these sentences? There's something slightly unnatural about them both.

1) works = произведения 2) works = заводы о чём вопрос?

Firstly, this word "works" has two totally differnet meanings here: 1. works = all the stuff an artist has given to the world The complete works of Shakespeare. 2. works = waterworks, gasworks, electricity works, etc. In both cases, "work" is incorrect! Work = what you do every day, or the actual work you do on a project, etc.