Why is it necessary to wait until the filter paper containing a compound is completely dry before weighing it? and how would it effect the theoretical yield? HIgher?? lower??

Answer 1

Think about it. Do you want to know the mass of the ppt + water or do you want to know the mass of the ppt only. If I've interpreted the question properly, the theoretical yield will be be affected but the actual yield will be higher (of course, since you are weighing water).