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प्रश्न
What are alloys?
What are alloys? Give two examples.
What is meant by an ‘alloy’?
Give two examples of an ‘alloy’.
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उत्तर १
An alloy is a homogeneous mixture of two or more metals or metals and non-metals. For example, brass is an alloy of copper and zinc.
For example:
- Stainless steel is an alloy of Nickel and Chromium.
- Amalgam is an alloy of Mercury.
- Brass is an alloy of Copper and Zinc.
- Bronze is an alloy of Copper and Tin.
- Solder is an alloy of Lead and Tin.
उत्तर २
An alloy is a homogenous mixture of two or more metals or a metal and a non–metal in definite proportion.
Examples:
- Brass – copper, and zinc.
- Stainless steel – iron, nickel, and chromium
Notes
Students should refer to the answer according to their question and prreferred marks.
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संबंधित प्रश्न
What is an alloy?
Give two examples of alloys with their chemical composition.
Give reasons:
Platinum, gold and silver are used to make jewellery.
Explain the term “corrosion” with an example. Write a chemical equation to show the process of corrosion of iron.
What is meant by galvanisation? Why is it done?
State two conditions for the rusting of iron.
In one method of rust prevention, the iron is not coated with anything. Which is this method?
The process of depositing a thin layer of zinc on iron articles is called ______.
Tiffin boxes are electroplated with ______ but car bumpers are electroplated with ______ to protect them from rusting.
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?
Name any two metals which do not corrode easily.
Name two metals which resist corrosion due to the formation of a thin, hard and impervious layer of oxide on their surface.
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 ______.
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.
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?
Mention two uses of the following metals and non-metals
Iron
Bronze is an alloy of ______.
Explain how the activity series accounts for each of the following:
tendency to corrosion
What is corrosion? What are necessary conditions for corrosion?
State under what conditions corrosion is faster ?
Explain with reason:
Roasting is carried out on sulphide ores and not on carbonate ores.
Observe the following picture a write down the chemical reaction with the explanation.
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.
Answer the following question.
List two properties of alloys.
Explain the term – rusting and give a word equation for the formation of rust. If polished iron nails are kept in three separate test tubes, state the contents in each test tube required, to prove the conditions for rusting.
Give reason for the following:
A suspension of rust is basic in nature.
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?
Which of the following method is used to prevent the accumulation of greenish layer on brass due to corrosion?
Corrosion of silver causes a black layer of _______.
Stainless steel is an alloy of _______.
Rusting of iron : Fe2O3 : : corrosion of copper : ______
Find the odd one out and give its explanation.
Match the columns.
| Group A | Group B |
| 1) Electroplating | a) Pressure cooker |
| 2) Anodising | b) Silver plated spoons |
| c) Coating of tin on copper | |
| d) Coating of Zinc on iron |
Write scientific reason.
Coins are made from metals and alloys.
Explain concept with example/explain with the help of a balanced equation.
Corrosion
What is rust?
Observe the following diagram and write answers.
- Name the method.
- Explain the method.
- Give two examples of this method.
Give solutions by giving examples of corrosion?
Give the equation for the formation of rust.
State two conditions necessary for rusting of iron.
Galvanisation is a method of protecting iron from rusting by coating it with a thin layer of ____________.
Which among the following alloys contain mercury as one of its constituents?
The diagram shows the reaction between metal and dil. acid.
What is the reason for different behaviour of Mg in test tube B?
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?
A man painted his main gate made up of iron, to
- prevent it from rusting.
- protect it from sun.
- make it look beautiful.
- make it dust free.
Which of the above statement(s) is/are correct?
Iron pillar near the Qutub Minar in Delhi is famous for the following facts. Which of these facts is responsible for its long stability?
Explain the following:
Lime water turns milky on passing carbon dioxide gas into it.
Give scientific reasons.
Silver amalgam is used for filling dental cavities.
Describe two changes that are harmful. Explain why you consider them harmful. How can you prevent them?
