How to stop facebook app from opening on its own?

Ok so i have the Sony Xperia play and every time i use the page killer app the facebook app is open along with about 10 other apps that i never opened from the last time i killed the facebook app...how do i stop it from opening on its own.....if your suggestion is log out of facebook...there's is no options menu on the top task bar there is no arrow to click and when u click on the facebook word theres no options menu to click and there is no log out anywhere!!! please someone help try to explain it well or use a video or something