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प्रश्न
You must have seen tarnished copper vessels being cleaned with lemon or tamarind juice. Explain why these sour substances are effective in cleaning the vessels.
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उत्तर
Copper reacts with moist carbon dioxide in the air to form copper carbonate, which causes a copper vessel to lose its shiny brown surface and form a green layer of copper carbonate. The citric acid present in lemon or tamarind neutralises the base copper carbonate and dissolves the layer. That is why tarnished copper vessels are cleaned with lemon or tamarind juice to give the surface its characteristic lustre.
\[\ce{2Cu + \underset{(Present in air)}{H2O + CO2 + O2} -> \underset{(green)}{\underset{Basic copper carbonate}{CuCO3.CU(OH)2}}}\]
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संबंधित प्रश्न
Name the following:
Metals which forms an amphoteric oxide.
Samples of four metals A, B, C and D were taken and added to the following solution one by one. The results obtained have been tabulated as follows.
| Metal | Iron (II) sulphate | Cooper (II) sulphate | Zinc sulphate | Silver nitrate |
| A | No reaction | Displacement | ||
| B | Displacement | No reaction | ||
| C | No reaction | No reaction | No reaction | Displacement |
| D | No reaction | No reaction | No reaction | No reaction |
Use the Table above to answer the following questions about metals A, B, C and D.
- Which is the most reactive metal?
- What would you observe if B is added to a solution of copper (II) sulphate?
- Arrange the metals A, B, C and D in the order of decreasing reactivity.
Which of the two metals is more reactive: copper or silver?
With the help of examples, describe how metal oxides differ from non-metal oxides.
Which of the following elements would yield a neutral oxide?
Na, S, C, K, H
Why does aluminium not react with water under ordinary conditions?
Why is white phosphorus kept immersed under water?
Can we keep sodium immersed under water? Why?
Name another metal oxide which behaves like aluminium oxide.
Hydrogen is not a metal but still it has been assigned a place in the reactivity series of metals. Why?
Name one metal which displaces silver from silver nitrate solution and one which does not.
One of the following is not a neutral oxide. This is:
(a) CO
(b) H2O
(c) N2O
(d) Na2O
A basic oxide will be formed by the element:
(a) K
(b) S
(c) P
(d) Kr
The metals which can produce amphoteric oxides are:
(a) sodium and aluminium
(b) zinc and potassium
(c) calcium and sodium
(d) aluminium and zinc
What is the cause of chemical bonding (or chemical combination) of atoms of elements?
Write the chemical equation of the above process.
Arrange the following metals in the increasing order of their reactivities:
Copper, Zinc, Aluminium, and Iron
Aluminium is used for making cooking utensils. Which of the following properties of aluminium are responsible for the same?
(i) Good thermal conductivity
(ii) Good electrical conductivity
(iii) Ductility
(iv) High melting point
A cable manufacturing unit tested few elements on the basisof their physical properties.
| Properties | W | X | Y | Z |
| Malleable | Yes | No | No | Yes |
| Ductile | Yes | No | No | Yes |
| Electrical conductivity | Yes | Yes | Yes | No |
| Melting Point | High | Low | Low | High |
Which of the above elements were dicarded for usage by the company?
