Advertisements
Advertisements
Question
Observe the following picture a write down the chemical reaction with the explanation.
Advertisements
Solution
The rusting of iron is an oxidation process. The rust on iron does not form by a simple reaction between oxygen and iron surface. The rust is formed by an electrochemical reaction. 'Fe' oxidises to Fe2O3.XH2O (Rust) is on one part of the iron surface, while oxygen gets reduced to H2O in another part of the surface. Different regions on the surface of iron become anode and cathode.
(1) Fe is oxidised to Fe2+ in the anode region.
\[\ce{Fe(s) -> Fe^{2+}(aq) + 2e^-}\]
(2) O2 is reduced to form water in the cathode region.
\[\ce{O2(g) + 4H^+(aq) + 4e^- -> 2H2O(l)}\]
When Fe2+ ions migrate from the anode region, they react with water and further get oxidised to form Fe3+ ions.
A reddish-coloured hydrated oxide is formed from Fe3+ ions. It is called rust. It collects on the surface.
\[\ce{2Fe^{3+}(aq) + 4H2O(l) -> Fe2O3.H2O(s) + 6H^+(aq)}\]
Due to various components of the atmosphere, oxidation of metals takes place, consequently resulting in their damage. This is called 'corrosion'. Iron rusts, and a reddish-coloured layer is collected on it. This is the corrosion of iron.
RELATED QUESTIONS
What is an alloy?
What is anodising? Give its applications.
What type of chemical reaction is involved in the corrosion of iron?
Name the metal which is used for galvanising iron.
Fill in the following blank with suitable word:
The corrosion of copper produces a .............. coating of basic copper carbonate on its surface
Fill in the following blanks with suitable words:
............ and .............. are necessary for the rusting of iron.
Why is an iron grill painted frequently?
What is corrosion?
Name two metals which resist corrosion due to the formation of a thin, hard and impervious layer of oxide on their surface.
What are the special properties of stainless steel?
Explain why, the galvanised iron article is protected against rusting even if the zinc layer is broken.
A common metal which is highly resistant to corrosion is:
(a) iron
(b) copper
(c) aluminium
(d) magnesium
In stainless steel alloy, iron metal is mixed with:
(a) Cu and Cr
(b) Cr and Ni
(c) Cr and Sn
(d) Cu and Ni
No chemical reaction takes place when granules of a rusty-brown solid A are mixed with the powder of another solid B. However, when the mixture is heated, a reaction takes place between its components. One of the products C is a metal and settles down in the molten state while the other product D floats over it. It was observed that the reaction is highly exothermic.
(a) What could the solids A and B be?
(b) What are the products C and D most likely to be?
(c) Write the chemical equation for the reaction between A and B leading to the formation of C and D. Mention the physical states of all the reactants and products in this equation and indicate the heat change which takes place.
(d) What is the special name of such a reaction? State one use of such a reaction.
(e) Name any two types of chemical reactions under which the above reaction can be classified.
Four metals P, Q, R and S are all obtained by the reduction of their oxides with carbon. Metal P is used to form a thin layer over the sheets of metal S to prevent its corrosion. Metal Q is used for electroplating tiffin boxes made of metal S whereas metal R is used in making car batteries. Metals Q and R form an alloy called solder. What are metals P, Q, R and S? How have you arrived at this conclusion?
Compare roasting and calcination.
No chemical reaction takes place when granules of a solid, A, are mixed with the powder of another solid, B. However when the mixture is heated, a reaction takes place between its components. One of the products, C, is a metal and settles down in the molten state while the other product, D, floats over it. It was observed that the reaction is highly exothermic.
(i) Based on the given information make an assumption about A and B and write a chemical equation for the chemical reaction indicating the conditions of reaction, physical state of reactants and products and thermal status of reaction.
(ii) Mention any two types of reactions under which above chemical reaction can be classified.
Write scientific reasons.
Lemon or tamarind is used for cleaning copper vessels turned greenish.
Give reason.
A wooden article should be polished.
Give reason.
Copper and brass utensils should be tinned.
State whether the statement given below is true or false. If false write the correct statement.
Either oxygen or moisture is essential for rusting.
Write a short note on Alloying.
Pressure cooker : Anodizing : : Silver plated spoons : _______
Write scientific reason.
Anodization method is useful for prevention of the corrosion of the aluminium.
What is rust?
Write a molecular formula for rust.
Observe the following diagram and write answers.
- Name the method.
- Explain the method.
- Give two examples of this method.
What is rust?
Amalgam is an alloy of ____________.
Iron pillar near the Qutub Minar in Delhi is famous for the following facts. Which of these facts is responsible for its long stability?
Galvanisation is a process used to prevent the rusting of which of the following?
State whether the following statement is true or false:
Ships suffer a lot of damage though they are painted.
Explain the following:
Lime water turns milky on passing carbon dioxide gas into it.
Explain the following:
Bubbles are produced when acetic acid is added to a solution of sodium hydrogencarbonate.
Give an example of a chemical reaction for the following situation:
Sound is produced
| A process of forming a thick oxide of aluminium when aluminium is exposed to air. This coat makes it resistant to corrosion. Resistance can be improved by making a layer of oxide thinker. In this technique, the aluminium article is the anode, and the electrolyte is sulphuric acid. The anode reaction results in the formation of a black-coloured film of aluminium oxide on the anode. By putting appropriate dyes in the electrolytic solution, both coloured surface with the decorative finish is achieved. Kitchen articles like anodised such as pressure cookers, pans and frames of sliding windows are applications of this technique. |
- Name the anode and electrolyte used in this technique.
- How can we make aluminium articles made resistant to corrosion?
- Name the technique used to coat the aluminium articles.
In ______ process a layer of molten tin is deposited on metals.
