Question

why tartaric acid gives tollens test?

Answer 1

Tartaric acid gives tollens test because it belongs to the Hydroxyl group. This test is carried out to differtiate between aldehydes and ketones.

These are the functional groups. The compound to be tested is added to the solution and the mixture is heated. 

Aldehydes are oxidized, , but ketones do not react, unless and until they are alpha-hydroxy-ketones.