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प्रश्न
What is tarnishing? Give an example.
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उत्तर
Tarnishing of metal articles:
Shiny metal surfaces and other articles lose their shining appearance due to chemical reactions on the surface. For example, silver articles become black on exposure to atmospheric air.
Similarly, brass vessels which contain copper as one of the constituents develop a greenish layer on exposure to air for a long time. This is due to a chemical reaction between copper and moist air to form basic copper carbonate and copper hydroxide.
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संबंधित प्रश्न
A chemical reaction is a temporary reaction.
Match the following.
| Spoilage | Decomposition |
| Ozone | Biocatalyst |
| Tarnishing | Oxygen |
| Yeast | Chemical reaction |
| Calcium oxide | Food |
What happens when an iron nail is placed in copper sulphate solution?
Explain how food items are spoiled by chemical reactions?
Explain the role of yeast in making cakes and buns in a bakery?
Do all the fruits and vegetables undergo browning? Explain.
Kumar is going to build a house. To purchase the iron rods required for construction, he visited an iron and steel shop nearby. The seller showed him some iron rods which are fresh and good. He also showed him little older iron rods which are brownish in appearance. The price of fresh rods is more than the older ones. The seller also gave some offers to older ones. Kumar’s friend Ramesh advised him not to buy the cheaper rods.
- Is Ramesh right in his suggestion?
- Could you explain the reason for his suggestion?
- What are the values shown by Ramesh?
Explain the environmental effects of chemical reactions?
Reason out
Ozone is produced naturally in the stratosphere.
An element ‘A’ on exposure to moist air turns reddish-brown and a new compound ‘B’ is formed. The substance ‘A’ and ‘B’ are:
