Usually when you chisel the tiles off most of the thin set mortar will be removed with it.
How to remove old tile adhesive from plaster wall.
Since not all will come off there will be an uneven layer of adhesive left behind.
Scrape the surface of the adhesive with a stiff bristle brush.
Wait several minutes and use a large scrapper to remove the mastic.
Step 3 wipe some tile adhesive remover over the surface of the wall.
If any adhesive gets stuck to the brush remove it by hand and continue until no more adhesive remains on the wall.
How to remove ceramic tile glue from a wall.
Apply some water to a small section of the adhesive.
If the adhesive is not cement based you could try sprinkling water to the wall to ease the scrapping process.
This can be accomplished using a pry bar to peel off the larger chunks.
All the the tiles have been removed by bolster chisel and as you will all know the bare plasterboard is now a mess and i need it to be clean before i can start putting the new tiles up.
If the adhesive used was organic mastic the water will begin to soften it allowing you to.
Apply an adhesive removing paste to the wall.
You will then have to pry off the leftover residue.