Yes, the noun mercy is an abstract noun, a word for compassion or forbearance shown especially to an offender or to one subject to one's power; lenient or compassionate treatment; a word for a concept.
Most merciful
Yes, the noun astonishment is an abstract noun, a word for an emotional reaction.
Is undergone an abstract noun
Concrete noun
The abstract noun is criticism.
The noun 'hopefulness' is an abstract noun, a word for an emotion.
The abstract noun is obligation.
Abstract noun of hopeless
Friendship has not abstract noun because It is a abstract noun
The abstract noun form is tourism.
The abstract noun for the adjective vacant is vacantness. Another abstract noun form is vacancy.