Question 15:
A man went door to door posing as a goldsmith. He promised to bring back the glitter
of old and dull gold ornaments. An unsuspecting lady gave a set of gold bangles to
him which he dipped in a particular solution. The bangles sparkled like new but their
weight was reduced drastically. The lady was upset but after a futile argument the
man beat a hasty retreat. Can you play the detective to find out the nature of the
solution he had used?
Answer
He must have dipped the gold metal in the solution of aqua regia − a 3:1 mixture of
conc. HCl and conc. HNO3. Aqua regia is a fuming, highly corrosive liquid. It dissolves
gold in it. After dipping the gold ornaments in aqua regia, the outer layer of gold gets
dissolved and the inner shiny layer appears. That is why the weight of gold ornament
reduced.
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