Corrosion and its Prevention Questions in English

(B) Iron articles are painted to prevent them from rusting.
Rusting is a chemical process that occurs when iron is exposed to moisture and oxygen in the air.
Applying a layer of paint creates a physical barrier that cuts off the contact between the iron surface and the atmospheric moisture and oxygen.
Since the presence of both moisture and oxygen is essential for the rusting process,painting effectively prevents the corrosion of iron.

(B) The reactivity of a metal is directly proportional to its tendency to corrode.
Metals that are less reactive,such as gold,silver,and platinum,do not react easily with atmospheric oxygen,moisture,or other chemicals.
Therefore,these metals are highly resistant to corrosion and do not corrode easily.

(A) The correct method is applying a coating of zinc (galvanization).
While applying grease or paint can prevent iron from rusting in general,these methods are not suitable for an iron frying pan.
When the pan is heated during cooking or washed repeatedly,the layers of grease or paint would be destroyed or contaminate the food.
Galvanization (coating with zinc) provides a more durable protective layer that is better suited for metallic cookware.

(N/A) Two ways to prevent the rusting of iron are:
$(i)$ Oiling,greasing,or painting: By applying oil,grease,or paint,the surface becomes waterproof,and the moisture and oxygen present in the air cannot come into direct contact with the iron. Hence,rusting is prevented.
$(ii)$ Galvanisation: An iron article is coated with a layer of zinc metal,which prevents the iron from coming into contact with oxygen and moisture. Hence,rusting is prevented.

(B) Galvanisation is a metallurgical process used to prevent the corrosion of iron or steel.
In this process,a protective layer of $Zinc$ is applied to the surface of the iron.
$Zinc$ is more reactive than iron,so it acts as a sacrificial anode,corroding in preference to the iron and thereby protecting the underlying metal from rusting.

(C) When copper articles are exposed to moist air for a long time,they react with atmospheric carbon dioxide,oxygen,and moisture.
This process leads to the formation of a green-colored layer on the surface of the copper.
This green coating is chemically known as basic copper carbonate,which has the formula $[CuCO_{3} \cdot Cu(OH)_{2}]$.
Therefore,the correct answer is a green coating of basic copper carbonate.

(N/A) $(i)$ The metal $X$ is Copper $(Cu)$. The process responsible for this change is known as corrosion.
$(ii)$ The green coating is Basic Copper Carbonate. Its chemical formula is $CuCO_{3} \cdot Cu(OH)_{2}$.
$(iii)$ Two important methods to prevent corrosion are:
$1$. Painting or oiling/greasing the surface.
$2$. Galvanisation or alloying.

(N/A) Corrosion of iron is a serious problem because it causes significant structural damage to bridges,iron railings,ships,and all objects made of metals,especially those made of iron. Every year,an enormous amount of money is spent to replace damaged iron structures.
$(b)$ Corrosion can be prevented by several methods:
$1$. Painting: Applying a coat of paint on the surface of the iron object.
$2$. Galvanization: Coating iron with a thin layer of zinc.
$3$. Electroplating: Depositing a layer of a non-corrosive metal over the iron surface.
$4$. Greasing or Oiling: Applying oil or grease to moving parts of machines.

(N/A) $(i)$ The metal has undergone corrosion.
$(ii)$ The metal is copper $(Cu)$.
$(iii)$ The green coating is basic copper carbonate,with the chemical formula $CuCO_{3} \cdot Cu(OH)_{2}$.
$(iv)$ Two ways to prevent this process are:
$1.$ Coating the metal surface with paint or oil/grease to prevent contact with moist air.
$2.$ Alloying the metal to increase its resistance to corrosion.

(N/A) Electrical wires are typically made of copper,which is an excellent conductor of electricity. However,copper is reactive and can undergo corrosion when exposed to moist air containing carbon dioxide,leading to the formation of a green layer of copper carbonate. Furthermore,copper is a metal and poses a risk of electric shock if touched directly. Plastic acts as an insulator,preventing electric shocks and protecting the metal wire from environmental corrosion.

(N/A) $(i)$ Aluminium does not corrode easily because,upon exposure to air,its surface forms a thin,protective,and non-reactive layer of aluminium oxide $(Al_2O_3)$. This layer prevents further oxidation of the metal.
$(ii)$ Copper vessels develop a green coating in the rainy season because copper reacts with moist carbon dioxide $(CO_2)$ and water vapor in the air to form a mixture of copper carbonate $(CuCO_3)$ and copper hydroxide $(Cu(OH)_2)$,which is green in color.

(N/A) Iron is galvanised with zinc to protect it from rusting. This is because zinc is more reactive (more electropositive) than iron,so it forms a protective layer that prevents corrosion. Copper is less reactive (less electropositive) than iron. Therefore,iron cannot be galvanised with copper because copper would actually accelerate the corrosion of iron if the coating were damaged.

(N/A) Anodising is an electrolytic process used to increase the thickness of the natural oxide layer on the surface of metal parts,typically aluminium.
During this process,a clean aluminium article is made the anode and is electrolysed with dilute sulphuric acid.
The oxygen gas evolved at the anode reacts with the aluminium to form a thicker,protective aluminium oxide layer,which makes the metal resistant to corrosion.

(A) To prevent an iron frying pan from rusting,we must consider the nature of the object.
Applying paint or grease is not suitable for a frying pan because these substances are not food-safe and would contaminate the food during cooking.
Applying a coating of zinc (galvanization) is also generally avoided for cooking utensils because zinc can react with acidic foods and leach into them,which is harmful.
However,in the context of standard multiple-choice questions regarding rust prevention,if we must choose the most appropriate method for a cooking surface,we often look for methods that do not involve toxic coatings.
Actually,none of the options provided are ideal for a frying pan. However,if this is a standard textbook question,it often expects 'Applying a coating of zinc' as a general rust prevention method,but for a frying pan,the most practical method is keeping it dry or seasoning it with oil. Given the options,if we must select one,'Applying a coating of zinc' is a standard method for iron,though not for frying pans. If the question implies general iron objects,all would work. Given the specific mention of a 'frying pan',this question is technically flawed as none are ideal. Assuming the question asks for general rust prevention: 'All of these' is the most logical choice for general iron items.

(C) Galvanisation is a process of applying a protective layer of zinc to steel or iron to prevent rusting.
Rusting is the oxidation of iron in the presence of oxygen and moisture.
By coating the surface with zinc,the metal is protected from direct contact with the atmosphere,thereby preventing corrosion.

(C) Galvanisation is a metallurgical process used to prevent the corrosion of iron or steel.
In this process,a thin layer of $Zinc$ is applied to the surface of the iron or steel object.
$Zinc$ is more reactive than iron,so it acts as a sacrificial anode,protecting the underlying iron from oxidation even if the coating is scratched.
Therefore,the correct answer is $Zinc$.

(B) The process of coating iron or steel with a thin layer of zinc to prevent rusting is known as galvanization. Therefore,iron coated with a layer of zinc is called galvanized iron. This protective layer acts as a barrier,preventing the iron from coming into contact with moisture and oxygen,which are necessary for the formation of rust.