biblatex: is it possible to combine two styles?

It is quite easy. biblatex allows you to choose a style for the bibliography, and a style for the citation. It is clearly written in the biblatex documentation.

bibstyle=chem-acs,citestyle=verbose-trad1

Instead of your style=chem-acs

As Martigan said, in principle it is possible to combine different styles for citations and bibliographies. I'll add two caveats:

• With the standard styles shipped with biblatex, certain combinations (especially with a non-default sorting scheme on top) may hamper the accessibility of bibliography entries. An example would be citestyle=numeric,bibstyle=authoryear,sorting=none (the last option will sort the entries according to their in-text citation order).

• Custom styles available on CTAN may be programmed in a way that the citation and bibliography style files are mutually dependend, and combining any of them with a different style may result in non-functional output or even outright error messages. An example are the styles included in the biblatex-dw package (an author-title style and a verbose style that offer features over and above that of the corresponding standard styles).