funeral chapel vs dead room

funeral chapel and dead room both are nouns.

Word	Noun	Adjective	Verb	Adverb
funeral chapel	Yes	No	No	No
dead room	Yes	No	No	No

As nouns, dead room is a hypernym of funeral chapel; that is, dead room is a word with a broader meaning than funeral chapel:

funeral chapel: a mortuary where those who knew the deceased can come to pay their last respects
dead room: a building (or room) where dead bodies are kept before burial or cremation

Other hypernyms of funeral chapel include morgue, mortuary.

funeral chapel (noun)	dead room (noun)
a mortuary where those who knew the deceased can come to pay their last respects	a building (or room) where dead bodies are kept before burial or cremation