Question

A metal 'x' become black in colour when exposed in air to form 'y'. It is used for making jewellery. It does not displace copper from CuSo4 and does not displace hydrogen with dilute acid. The metal is used in filling dental cavities .
identify the metal 'x' and compound 'y' ,give reason for the properties?

Answer 1

Answer:

Explanation: The compounds namely are X : Silver, Y : Silver sulphide.

Silver is a metal which is considered to be a near noble element. Noble elements mean the type of elements which have very low reactivity.

Silver ranks in the last stages of the reactivity series. It is below Hydrogen in this series. The rule says that only higher members can replace the lower ones and not vice versa. Hence it cannot displace Hydrogen. The black compound is kind of rust of Silver.