One day Kavita went to a jewellers shop with her mother. Her mother gave an old metal jewellery to the goldsmith to polish. Next day when they brought the jewellery back, they found that there was a slight loss in its weight. Can you suggest a reason for the loss in weight?

Explanation

Gold is a noble metal which does not react with any strong acid like HCl, `HNO_(3)` and `H_(2)SO_(4)`, but it can be dissolved in aqua regia (a mixture of conc. HCl and conc. `HNO_(3)` in the ratio of 3:1) due to the formation of nascent chlorine which reacts with these metals to form metal chlorides.

`Au+3Cl to AuCl_(3),Pt+4Cl to PtCl_(4)`
Aqua regia highly corrosive and fuming liquid. So, some amount of gold remained dissolved in aqua regia in the form of its chloride which caused loss in its weight.