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प्रश्न
Write scientific reasons.
Lemon or tamarind is used for cleaning copper vessels turned greenish.
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
Write two methods of preventing the rusting of iron.
Why do we apply paint on iron articles?
Explain why rusting of iron objects is faster in coastal areas than in deserts.
Write a chemical equation to show the process of corrosion of iron.
What special name is given to their corrosion of iron?
What type of chemical reaction is involved in 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?
State two conditions for the rusting of iron.
Fill in the following blanks with suitable words:
Tiffin boxes are electroplated with .............. but car bumpers are electroplated with ............... to protect them from rusting.
What is the corrosion of iron known as?
What are the special properties of stainless steel?
Explain why, the galvanised iron article is protected against rusting even if the zinc layer is broken.
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(a) Cu and Sn
(b) Cu and Pb
(c) Pb and Sn
(d) Zn and Cu
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(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.
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(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.
Observe the following picture a write down the chemical reaction with the explanation.
Answer the following question.
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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.
Write three methods of preventing rusting of iron.
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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.
Either oxygen or moisture is essential for rusting.
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_______ forms a green colour in the water.
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Complete flow chart given below.
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| 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 |
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Give an example of a chemical reaction for each of the following situations:
Sound is produced
