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प्रश्न
Give scientific reasons.
Silver amalgam is used for filling dental cavities.
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उत्तर
Because silver amalgam melts at low temperatures and may easily fill cavities, it is used to fill cavities.
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संबंधित प्रश्न
What is an alloy?
Which metals do not corrode easily?
Write a chemical equation to show the process of corrosion of iron.
What special name is given to the corrosion of iron?
Name any three objects (or structures) which are gradually damaged by the corrosion of iron and steel.
What is meant by galvanisation? Why is it done?
Explain why, iron sheets are coated with zinc.
Fill in the following blank with suitable word:
The process of depositing a thin layer of zinc on iron articles is called .............
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 five methods of preventing rusting of iron.
A common metal which is highly resistant to corrosion is:
(a) iron
(b) copper
(c) aluminium
(d) magnesium
If copper is kept exposed to damp air for a considerable time, it gets a green coating on its surface. This is due to the formation of:
(a) hydrated copper sulphate
(b) copper oxide
(c) basic copper carbonate
(d) copper nitrate
Mention two uses of the following metals and non-metals
Iron
Bronze is an alloy of ______.
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.
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 ..................................................................
Find the odd man out:
What are the adverse effects of corrosion?
What is ‘rusting’?
Give reason.
An iron article should be given a coat of paint
Give reason.
Copper and brass utensils should be tinned.
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?
When one of the metals in an alloy is mercury the alloy is called _______.
Pressure cooker : Anodizing : : Silver plated spoons : _______
Draw a neat labelled diagram.
Electroplating
What is rust?
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?
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.
Give preventive methods by giving examples of corrosion?
Identify the correct statement from the following:
Explain the following:
Lime water turns milky on passing carbon dioxide gas into it.
Explain the chemical reactions in rusting of iron.
| 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.
