Question

Explain why surface of some metal acquires Dull appearance after exposed for ling time in air.​

Answer 1

Hey mate !!

✨Surface of some metals acquires a dull appearance because they react with air or water in the environment to form undesirable compounds (such as Oxides) . This process is called Corrosion.

✨For example:- silver tarnishes, copper Develops green coating, iron loses its lustre. The Corrosion of iron is called Rusting. The chemical formula of Rust is Fe2O3.xH2O.

Answer 2

$\huge\mathfrak{Answer}$

When the metal objects are left outside the dull appearance is seen because of the layer of oxides formed on it.

✔️The Thin layers of oxides are formed ...

✔️Even ,Carbonate and Sulphide layers are formed .

•Take example of Iron

When iron particles are left outside , the brown rust is formed ,here it is the oxide of iron which is deposited over the iron particle.

✔️This is also called Corrosion.

✔️To prevent this ,we can

✒️Paint the items

✒️Galvanise the items

✒️Apply oil or grease.

✏️Iron gates are mostly painted .