空からになる

Meanings

1

expression, godan verb (-ru)

become empty; be emptied

Describes a container, space, or abstract thing becoming empty, often naturally or as a result of an action.

空からにする
空にする is transitive (to empty something), while 空になる is intransitive (to become empty).
空あく
空く also means 'to become empty', but is a single verb; 空になる is a more explicit phrase often used for emphasis or clarity.

Phrase composed of 空 (から, 'empty') + に (particle) + なる (become).