is το πιπέρι in accusative case or nominative case when you ask someone to pass you the pepper? Or you want to order the pepper at a restaurant?
It is in the accusative
Looks like there are two possible translations: άλας (salt); το αλάτι (the salt).
Yes. Both can be used for cooking salt (with a strong preference to αλάτι) but only άλας is used for the chemistry term of "salt".
What's the difference between
Το πιπερι and Η πιπεριά (which I'm sure I've just used!)