Put on thick work gloves and safety glasses to protect yourself from flying pieces of mortar. If you are working near a sink or tub, lay a tarp over the drain to prevent the mortar from falling into it and clogging it up.
Place the blade of a chisel scraper up to the mortar and position it so the blade is angled under a chunk of mortar. Hit the head of the scraper with a hammer using firm force to drive the blade up under the mortar, thus chipping it off.
Move on to another section of mortar and repeat the process of hitting the chisel blade with the hammer to dislodge another chunk.
Set the hammer aside once only small amounts of mortar remain, and simply move the scraper back and forth to dislodge the remaining mortar. Continue this process along the entire area until no more mortar remains on the wall.
Sweep up all of the loose mortar and scoop it up in a dust pan. Pour the mortar into a waste bin to dispose of it. Vacuum the bathroom area thoroughly with a shop vac to remove any mortar dust.