tile on wall

i have an adobe house so my master bathroom has tile on an exterior wall. there is an existing layer of concrete that i removed the tile from. the problem is it left some mortar. this makes my wall not flat for new tile install. what can i do, i have tried scraping and it doesnt work. can i belt sand? or is skim coating with mortar the only option?

You'll probably get some ideas here, but I'd try www.johnbridge.com I think you'll get more ideas faster. Trying to flatten the wall is possible, but may not be necessary, except to make it easier to set the tile evenly. You could probably chip it off, but it may take out chunks. Somebody over there has probably done this and will have some ideas. Unlike floor tile where it should have 100% coverage, that isn't as important (still desireable) on a wall. My unprofessional opinion.

thanks for the website it was a big help!