Question

why did golds weight reduce after polishing

Answer 1

Whenever we give a gold ornament to a goldsmith for polish, he washes the ornament in the solution called aqua regia which is able to dissolve gold . so a thin layer of gold get dissolve in that solution and we find a shiny surface bcoz of the next layer. and only because a layer get dissolves in it, we find a difference in weight of the ornament.

Answer 2

There is a loss of weight in the gold after polish because goldsmith reacts the jewellery with acid to shine.In the process, a little amount of gold is lost.