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प्रश्न
Write scientific reason.
Coins are made from metals and alloys.
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उत्तर
- Coins are made from metals and alloys because metals and their alloys possess the property of malleability. So, they can be hammered into flat shape without breaking.
- Metals and alloys used for making coins should be corrosion resistance and bright in colour. They should also be hard and wear resistance.
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संबंधित प्रश्न
Which metals do not corrode easily?
What are alloys?
Which of the following methods is suitable for preventing an iron frying pan from rusting?
Explain why rusting of iron objects is faster in coastal areas than in deserts.
Explain why Iron sheets are coated with zinc during galvanization.
Explain why, iron sheets are coated with zinc.
State two conditions for the rusting of iron.
The corrosion of copper produces a ______ coating of basic copper carbonate on its surface.
______ and ______ are necessary for the rusting of iron.
What is corrosion?
Explain why, when a copper object remains in damp air for a considerable time, a green coating is formed on its surface. What is this process known as?
A common metal which is highly resistant to corrosion is ______.
Brass is an alloy of ______.
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.
- What could the solids A and B be?
- What are the products C and D most likely to be?
- 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.
- What is the special name of such a reaction? State one use of such a reaction.
- Name any two types of chemical reactions under which the above reaction can be classified.
Complete the process of iron rusting by filling the blanks. Suggest a way to prohibit the process.
The iron rust is formed due to........................... reaction. Different
regions on iron surface become anode and cathode.
Reaction on anode region :
`F_e(s) → Fe^(2+) (aq) +2e^-`
Reaction on anode region :
`O_2(g) + 4H^+(aq) +............................ → 2H_2 O (l) `
When Fe2+ ions migrate from anode region they react with ................... to form Fe3+ ions.
A reddish coloured hydrated oxide is formed from ............... ions. It is called rust.
`2Fe_(3+) (aq) + 4H_2O(l) → ................. + 6H_+(aq) `
A way to prevent rusting ..................................................................
Answer the following question.
a) What is meant by corrosion?
b) Write names of any two methods of prevention of corrosion.
c) In which method, metal like copper, aluminium are coated with a thin layer of their oxides by means of electrolysis.
d) Explain this method with diagram.
Give reason.
Copper and brass utensils should be tinned.
Give reason for the following:
A suspension of rust is basic in nature.
State whether the statement given below is true or false. If false write the correct statement.
Graphite is a lustrous non-metal which conducts electricity.
Observe the following picture and answer the following questions:
- What is rust?
- Write the chemical formula of rust.
- Write the reaction of oxidation of iron at the anode.
- Write the reaction of oxidation of iron at the cathode.
- What is corrosion?
_______ is an alloy made from iron, carbon and chromium.
When one of the metals in an alloy is mercury the alloy is called _______.
Rusting of iron : Fe2O3 : : corrosion of copper : ______
Find the odd one out and give its explanation.
Write the name.
Method used to prevent corrosion of copper.
Draw a neat labelled diagram.
Anodizing
Complete flow chart given below.
What is rust?
Write a molecular formula for rust.
Observe the following figure and write the answer of the question.
- Which process is shown in the figure?
- Explain the chemical reaction shown in the figure.
- Write the reactions on anode and cathode.
What is rust?
State two conditions necessary for rusting of iron.
Alloys are homogeneous mixtures of a metal with a metal or non-metal. Which among the following alloys contain non-metal as one of its constituents?
Generally, when metals are treated with mineral acids, hydrogen gas is liberated but when metals (except Mn and Mg), treated with HNO3, hydrogen is not liberated, why?
Iron pillar near the Qutub Minar in Delhi is famous for the following facts. Which of these facts is responsible for its long stability?
Give an example of a chemical reaction for the following situation:
Sound is produced
