at peace vs at rest

at peace and at rest both are adjectives.

Word	Noun	Adjective	Verb	Adverb
at peace	No	Yes	No	No
at rest	No	Yes	No	No

As adjectives, at peace and at rest are synonyms defined as:

Other synonyms of at peace include asleep, deceased, departed, gone.

at peace (adjective)	at rest (adjective)
dead	in a state of repose or especially sleep
	dead