It's masculine in expressions like qualcos'altro, something else.
Thanks for solving these otherwise unsolvable questions
Why doesn't pulito need to agree with qualcosa? Or is qualcosa masculine?
partitive complement is required to agree with"qualcosa" in masculine. example: "qualcosa di caldo" (something hot), or "qualcosa di pulito" (something clean).
Trying to work out what the difference actually is between hai and avete such as in this sentence (both were accepted
"You have" can be translated as the singular "tu hai", the plural "voi avete" or the formal "Lei ha". Only context can tell you what to use.