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प्रश्न
Write scientific reasons.
Lemon or tamarind is used for cleaning copper vessels turned greenish.
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उत्तर
- Copper vessels turned greenish due to the formation of copper carbonate layer.
- The citric acid present in the lemon or tamarind neutralizes the basic copper carbonate and dissolves the layer.
- That is why tarnished copper vessels are cleaned with lemon or tamarind juice to give the surface of the copper vessel its characteristic lustre.
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संबंधित प्रश्न
Give two examples of alloys with their chemical composition.
Write two methods of preventing the rusting of iron.
Which metals do not corrode easily?
Which of the following methods is suitable for preventing an iron frying pan from rusting?
Give reasons:
Platinum, gold and silver are used to make jewellery.
Explain why rusting of iron objects is faster in coastal areas than in deserts.
What is anodising? Give its applications.
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?
Name the metal which is used for galvanising iron.
The corrosion of iron is called ______.
Tiffin boxes are electroplated with ______ but car bumpers are electroplated with ______ to protect them from rusting.
What is the corrosion of iron known as?
With the help of labelled diagrams, describe an activity to find out the conditions under which iron rusts.
What are the constituents of stainless steel?
Bronze is an alloy of ______.
What is corrosion? What are necessary conditions for corrosion?
Compare roasting and calcination.
Answer the following question:
What is corrosion? Do gold ornaments corrode? Justify.
What is ‘rusting’?
Give reason.
A wooden article should be polished.
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.
_______ is an alloy made from iron, carbon and chromium.
Corrosion of silver causes a black layer of _______.
Bronze : _______ : : Stainless steel : Fe + Cr + C
Find the odd one out and give its explanation.
Draw a neat labelled diagram.
Electroplating
Complete flow chart given below.
Give preventive methods by giving examples of corrosion?
Amalgam is an alloy of ____________.
The table shown below gives information about four substances: A, B, C and D.
| SUBSTANCE | MELTING POINT (K) | ELECTRICAL CONDUCTIVITY | |
| SOLID | LIQUID/ AQUEOUS | ||
| A | 295 | Good | Good |
| B | 1210 | Poor | Good |
| C | 1890 | Poor | Good |
| D | 1160 | Poor | Poor |
Identify Ionic compounds from the above given substances.
Identify the correct statement from the following:
Explain the following:
Bubbles are produced when acetic acid is added to a solution of sodium hydrogencarbonate.
| 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.
