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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
Write two methods of preventing the rusting of iron.
Give reasons:
Platinum, gold and silver are used to make jewellery.
Choose the correct answer from the options given below:
Heating an ore in a limited supply of air or in the absence of air at a temperature just below its melting point is known as
A. Smelting
B. Ore-dressing
C. Calcination
D. Bessemerisation
What is anodising? Give its applications.
What type of chemical reaction is involved in the corrosion of iron?
The chemical reaction involved in the corrosion of iron metal is that of ______.
Fill in the following blank with suitable word:
The process of depositing a thin layer of zinc on iron articles is called .............
Fill in the following blanks with suitable words:
............ and .............. are necessary for the rusting of iron.
What is meant by 'rusting of iron'? With the help of labelled diagrams, describe an activity to find out the conditions under which iron rusts.
Give the constituents and one use of brass.
Name an alloy of copper. State its chemical composition and any one use.
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?
Explain why, the galvanised iron article is protected against rusting even if the zinc layer is broken.
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.
Name the metal which is a constituent of blood pigment?
Corrosion can be an advantage in some case.Explain ?
Write scientific reasons.
Lemon or tamarind is used for cleaning copper vessels turned greenish.
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 ..................................................................
Identify the process shown in the diagram and explain it in short
Find the odd man out:
What are the adverse effects of corrosion?
Give reason.
An iron article should be given a coat of paint
Give a reason why rust turns moist red litmus blue.
To prevent corrosion of iron and steel _______ method is used.
Pressure cooker : Anodizing : : Silver plated spoons : _______
Bronze : _______ : : Stainless steel : Fe + Cr + C
Observe the following diagram and give answers.
- Name this method of prevention of corrosion.
- For prevention of which metal this method is used?
- What is used as anode in this method?
What is rust?
State whether the following statement is true or false:
Ships suffer a lot of damage though they are painted.
Give an example of a chemical reaction for the following situation:
Sound is produced
Give scientific reasons.
Silver amalgam is used for filling dental cavities.
In ______ process a layer of molten tin is deposited on metals.
