Which metals do not corrode easily?

An element reacts with oxygen to give a compound with a high melting point. This compound is also soluble in water. The element is likely to be

Which gas is produced when dilute hydrochloric acid is added to a reactive metal? Write the chemical reaction when iron reacts with dilute $H_2SO_4$.

$A$ 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?

Give reasons: Platinum,gold,and silver are used to make jewellery.

In the electrolytic refining of a metal $M$,what would you take as the anode,the cathode,and the electrolyte?