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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?
Burning of fossil fuels is responsible for global warming. Justify the statement.
Do all the fruits and vegetables undergo browning? Explain.
Classify the following day-to-day activities based on chemical reactions by physical contact, solutions of reactants, heat, light, electricity, and catalyst.
- Burning of crackers during festivals
- Fading of coloured clothes on drying under sunlight.
- Cooking of eggs.
- Charging of batteries.
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:
