Advertisements
Advertisements
प्रश्न
Give reasons:
Platinum, gold and silver are used to make jewellery.
Give a reason for the following:
Silver, gold and platinum are used to make jewellery.
उत्तर
- Gold, silver, and platinum are the least reactive metals. They do not react with air, water, acids, alkalis, or other gases in the environment, so their shine lasts for years.
- Due to their bright lustre and resistance to corrosion, gold, silver, and platinum are used to make jewellery.
APPEARS IN
संबंधित प्रश्न
Why do we apply paint on iron articles?
Explain the terms Corrosion
What special name is given to their corrosion of iron?
The chemical reaction involved in the corrosion of iron metal is that of:
(a) oxidation as well as displacement
(b) reduction as well as combination
(c) oxidation as well as combination
(d) reduction as well as displacement
Name the metal which is used for galvanising iron.
Fill in the following blank with suitable word:
The corrosion of iron is called ................
Fill in the following blanks with suitable words:
Tiffin boxes are electroplated with .............. but car bumpers are electroplated with ............... to protect them from rusting.
Fill in the following blanks with suitable words:
............ and .............. are necessary for the rusting of iron.
Explain why, through aluminium is more reactive than iron, yet there is less corrosion of aluminium when both are exposed to air.
What is meant by 'rusting of iron'? With the help of labelled diagrams, describe an activity to find out the conditions under which iron rusts.
Give the constituents and one use of brass.
Name five methods of preventing rusting of iron.
What are the constituents of stainless steel?
Explain why, when a copper object remains in damp air for a considerable time, a green coating is formed on its surface. What is this process known as?
Explain why, the galvanised iron article is protected against rusting even if the zinc layer is broken.
Name a common metal which is highly resistant to corrosion.
A common metal which is highly resistant to corrosion is:
(a) iron
(b) copper
(c) aluminium
(d) magnesium
Bronze is an alloy of ______.
Name the metal which is a constituent of plant pigment?
What is corrosion? What are necessary conditions for corrosion?
Corrosion can be an advantage in some case.Explain ?
No chemical reaction takes place when granules of a solid, A, are mixed with the powder of another solid, B. However when the mixture is heated, a reaction takes place between its components. One of the products, C, is a metal and settles down in the molten state while the other product, D, floats over it. It was observed that the reaction is highly exothermic.
(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.
Write scientific reasons.
Lemon or tamarind is used for cleaning copper vessels turned greenish.
Explain the term – rusting and give a word equation for the formation of rust. If polished iron nails are kept in three separate test tubes, state the contents in each test tube required, to prove the conditions for rusting.
Give a reason why rust turns moist red litmus blue.
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 _______.
Match the columns.
| Group A | Group B |
| 1) Electroplating | a) Pressure cooker |
| 2) Anodising | b) Silver plated spoons |
| c) Coating of tin on copper | |
| d) Coating of Zinc on iron |
Explain concept with example/explain with the help of a balanced equation.
Corrosion
Observe the following diagram and give answers.
- Name this method of prevention of corrosion.
- For prevention of which metal this method is used?
- What is used as anode in this method?
Give the equation for the formation of rust.
State two conditions necessary for rusting of iron.
The iron pillar near the Qutub Minar in Delhi is famous for the following facts. Which of these facts is responsible for its long stability?
