Write a test to differentiate between pentan$-2-$one and pentan$-3-$one.

Pentan$-2-$one contains a $CH_3CO-$ group,therefore it gives a positive iodoform test with $I_2/NaOH$,forming a yellow precipitate of iodoform $(CHI_3)$.
Pentan$-3-$one does not contain a $CH_3CO-$ group,therefore it does not give a positive iodoform test.
Reaction:
$CH_3CH_2CH_2COCH_3 + 3I_2 + 4NaOH \rightarrow CH_3CH_2CH_2COONa + CHI_3 \text{ (yellow ppt)} + 3NaI + 3H_2O$
$CH_3CH_2COCH_2CH_3 + I_2/NaOH \rightarrow \text{No reaction}$