1)        Whose = de quem, do qual ( asks about possession )

         Ex) Whose car did you borrow? I borrowed Karen's car

2)         Which = que, o que, qual, o qual

        Ex)  Tom: May I borrow a pen from you?

                Ann: Sure. I have two pens. This pen has black ink. That pen has red ink.

                Which pen do you want? or

                 Which one do you want? or

                 Which        do you want?