iron
articles are shiny when new, but get coated with a reddish powder
en left for some time. This process is commonly known as Rusting of
Iron.
on
When a metal is attacked by substances around it such as
moisture, acids etc., it is said to be corroded and this pro
corrosion. The black coating on silver and the green coating
are
other examples of corrosion.
3.1
Name the green coating on copper.
3.2 If there are two type of solution. One is low pH solution and other
is high pH solution, in which solution metal will corrode faster?
Justify your answer.
3.3 The removal of Black coating on silver involves which type of
action, Physical or Chemical? Justify your answer.
3.4 Is there any change in the mass of an object after corrosion? 1
X-Science (1)
Answers
Answer:
1. green coating is copper oxide
2. in solution of low ph corrosion occur faster
3. removal of black coating from silver requires chemical process
4. Corrosion of a block of metal - Iron to Iron Oxide (rust), Aluminum to Bauxite, Cooper to Cupric-oxide, or otherwise - does not change the weight of the metal in the system. If does change the weight of the object itself. As long as the object is undisturbed the its weight will increase due to the addition of oxygen molecules.
The density of the object will go down for a number of reasons: oxygen is lighter than the metal and the resulting molecule is larger.
Also remember that metallic oxides easily slough off the parent object. As the parent object is handled or otherwise disturbed it is relatively easy to remove some of the the loose material. This will make it appear that the original object has lost weight, but it is no longer the same object.
Answer:
i) copper oxide
ii) occur faster
iii) chemical process
iv) Iron oxide , Aluminum to baxite , copper to cuprie - oxide .