Advertisements
Advertisements
प्रश्न
Write scientific reasons.
Lemon or tamarind is used for cleaning copper vessels turned greenish.
Advertisements
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.
APPEARS IN
संबंधित प्रश्न
What is an alloy?
Give two examples of alloys with their chemical composition.
Explain the term corrosion.
Give reasons:
Platinum, gold and silver are used to make jewellery.
Two methods by which rusting of iron can be prevented are ______ and ______.
Choose the correct answer from the options given below:
Heating an ore in a limited supply of air or in the absence of air at a temperature just below its melting point is known as
A. Smelting
B. Ore-dressing
C. Calcination
D. Bessemerisation
What is meant by galvanisation? Why is it done?
The corrosion of copper produces a ______ coating of basic copper carbonate on its surface.
______ and ______ are necessary for the rusting of iron.
Name any two metals which do not corrode easily.
Name two metals which resist corrosion due to the formation of a thin, hard and impervious layer of oxide on their surface.
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.
Mention two uses of the following metals and non-metals
Iron
Bronze is an alloy of ______.
Choose the correct alternative and rewrite the following:
Iron is _____________________.
What is ‘rusting’?
Give reason.
A wooden article should be polished.
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.
Write a short note on Alloying.
Pressure cooker : Anodizing : : Silver plated spoons : _______
Find the correlation:
Bronze : ______ :: Tin : Cu+Zn.
Find the odd one out and give its explanation.
Write the name.
An alloy of copper and tin-
Write the name.
Method used to present corrosion of copper.
Write scientific reason.
On exposure to air, silver articles turn blackish after some time.
Write scientific reason.
Coins are made from metals and alloys.
Draw a neat labelled diagram.
Anodizing
Complete flow chart given below.
Give the equation for the formation of rust.
Galvanisation is a method of protecting iron from rusting by coating it with a thin layer of ____________.
The diagram shows the reaction between metal and dil. acid.
What is the reason for different behaviour of Mg in test tube B?
Marble’s popularity began in ancient Rome and Greece, where white and off-white marble were used to construct a variety of structures, from hand-held sculptures to massive pillars and buildings.
The substance not likely to contain CaCO3 is:
A man painted his main gate made up of iron, to
- prevent it from rusting.
- protect it from sun.
- make it look beautiful.
- make it dust free.
Which of the above statement(s) is/are correct?
Iron pillar near the Qutub Minar in Delhi is famous for the following facts. Which of these facts is responsible for its long stability?
Explain the chemical reactions in rusting of iron.
| A process of forming a thick oxide of aluminium when aluminium is exposed to air. This coat makes it resistant to corrosion. Resistance can be improved by making a layer of oxide thinker. In this technique, the aluminium article is the anode, and the electrolyte is sulphuric acid. The anode reaction results in the formation of a black-coloured film of aluminium oxide on the anode. By putting appropriate dyes in the electrolytic solution, both coloured surface with the decorative finish is achieved. Kitchen articles like anodised such as pressure cookers, pans and frames of sliding windows are applications of this technique. |
- Name the anode and electrolyte used in this technique.
- How can we make aluminium articles made resistant to corrosion?
- Name the technique used to coat the aluminium articles.
