What is the ruling on reading the Qur'an in a room that contains a chair always used for placing impure clothes until they are washed?

There is no harm in praying on a mat, part of which is impure, if the place where the worshiper prays is pure. The intent is the purity of the place touched by the worshiper's body parts. The presence of impurity on the edges or underneath the mat does not matter.