Distinction between pairs of compounds
Benzaldehyde `(C_(6)H_(5)CHO)` and acetone `(CH_(3)COCH_(3))`
(a) Tollens' reagent test.
(b) Iodoform test.

Explanation

Following tests help to distinguish these :
(a) Benzaldehyde when heated with Tollens. reagent (ammoniacal silver nitrate solution), silver mirror is formed. Acetone does not give this test.
`underset("Benzaldehyde")(C_(6)H_(5)CHO)+2[Ag(NH_(3))_(2)]^(+)+3OH^(-)`
`rarrC_(6)H_(5)COO^(-)+underset("Silver mirror")(2Agdarr+)4NH_(3)+2H_(2)O`
(b) Acetone is a methyl ketone. So, it reacts with `I_(2)//NaOH` or NaOI to form iodoform (yellow ppt.) Benzaldehyde does not give this test.