Vapour of an organic compound X, when passed over hot reduced copper at 573 K, gave acetone. The formula of X _______.

When a mixture of acetic acid and formic acid vapour is passed over MnO catalyst at 573 K, _________ is formed.

When acetaldehyde is treated with aluminium ethoxide, _________ is formed.

Formic acid when heated with conc. H₂SO₄ produces _________.