Give one chemical test to distinguish between the following pairs of compounds:-(1) Methylamine and dimethylamine(2) Secondary and tertiary amines (3) Ethylamine and aniline(4) Aniline and benzaldehyde (5) Aniline and N-methylaniline

Methylamine and Dimethylamine:

Hinsberg Test: To distinguish between methylamine and dimethylamine, you can use the Hinsberg test. In this test, you react the amine with benzenesulfonyl chloride (Hinsberg reagent). Methylamine will react to form a soluble sulfonamide, while dimethylamine will not react, or if it does, it will form an insoluble sulfonamide. This difference in solubility helps distinguish between them.
Secondary and Tertiary Amines:

Hofmann Bromamide Reaction: You can use the Hofmann Bromamide Reaction to differentiate between secondary and tertiary amines. When treated with bromine water and sodium hydroxide, secondary amines will produce a white precipitate of the corresponding N-substituted amide, while tertiary amines will not react with bromine water under these conditions.
Ethylamine and Aniline:

Diazotization Reaction: Ethylamine does not undergo diazotization readily, whereas aniline can be diazotized using nitrous acid (HNO2) to form a diazonium salt. By adding sodium nitrite (NaNO2) and hydrochloric acid (HCl) to the solution and observing the formation of a colored diazonium salt, you can distinguish aniline from ethylamine.
Aniline and Benzaldehyde:

Schiff's Reagent Test: To distinguish between aniline and benzaldehyde, you can use Schiff's reagent. Schiff's reagent contains fuchsin sulfurous acid, and it reacts with primary aromatic amines like aniline to form a colored product. Benzaldehyde will not react with Schiff's reagent, so you will not observe the color change with benzaldehyde.
Aniline and N-Methylaniline:

Diazotization Reaction: Similar to the test for ethylamine and aniline, you can use the diazotization reaction to differentiate between aniline and N-methylaniline. Aniline can be diazotized to form a diazonium salt, whereas N-methylaniline does not readily undergo this reaction.
Always exercise caution and follow safety procedures when working with chemicals, as some of these reactions may involve hazardous reagents.