Question

Why polished calorimeter preferred to use

Answer 1

Calorimeter is a device which is used to measure the amount of heat associated in a chemical process, for the accurate measurement of heat, we don't want that any part of heat is reflected from the device, that's why we polish the calorimeter as we know that black color is consider as ideal black body, and absorb all the radiation impinges on it.

That's why polished calorimeter with a black color so that it can absorb all the radiation impinges on it, and we get the accurate measurement of heat associated in a process.