n-Propyl alcohol and Isopropyl alcohol can be chemically distinguished by which reagent:

n-Propyl alcohol (propan-1-ol) is a primary alcohol, while Isopropyl alcohol (propan-2-ol) is a secondary alcohol. They can be distinguished by their oxidation products using a strong oxidising agent like acidified Potassium Dichromate ($K_2Cr_2O_7$).

1. Primary Alcohols: Oxidise to form aldehydes and then carboxylic acids containing the same number of carbon atoms. n-Propyl alcohol gives propanal and then propanoic acid.
2. Secondary Alcohols: Oxidise to form ketones with the same number of carbon atoms. Isopropyl alcohol gives propanone (acetone).
3. Distinction: While both turn the dichromate solution from orange to green (reduction of $Cr^{6+}$ to $Cr^{3+}$), the products are different (acid vs ketone). Ketones are resistant to further oxidation, whereas primary alcohols/aldehydes oxidise easily to acids.

(Note: $PCl_5$ reacts with both to give alkyl chlorides. Ozonolysis is a test for alkenes. Reduction is not a standard distinguishing test for alcohols).