Advertisements
Advertisements
Question
Write scientific reasons.
Lemon or tamarind is used for cleaning copper vessels turned greenish.
Advertisements
Solution
- 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
RELATED QUESTIONS
Explain the term corrosion.
What are alloys?
Which of the following methods is suitable for preventing an iron frying pan from rusting?
Two methods by which rusting of iron can be prevented are ______ and ______.
What special name is given to the corrosion of iron?
Name any three objects (or structures) which are gradually damaged by the corrosion of iron and steel.
Explain why, iron sheets are coated with zinc.
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.
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.
In stainless steel alloy, iron metal is mixed with:
(a) Cu and Cr
(b) Cr and Ni
(c) Cr and Sn
(d) Cu and Ni
A metal X which is resistant to corrosion is produced by the electrolysis of its molten oxide whereas another metal Y which is also resistant to corrosion is produced by the reduction of its oxide with carbon. Metal X can be used in powder form in thermite welding whereas metal Y is used in making cathodes of ordinary dry cells.
(a) Name the metals X and Y.
(b) Which of the two metals is more reactive : X or Y?
(c) Name one ore or metal X. Also write its chemical formula.
(d) Name one ore or metal Y. Also write its chemical formula.
(e) Name one alloy of metal X and one alloy of metal Y.
Compare roasting and calcination.
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.
Answer the following question.
a) What is meant by corrosion?
b) Write names of any two methods of prevention of corrosion.
c) In which method, metal like copper, aluminium are coated with a thin layer of their oxides by means of electrolysis.
d) Explain this method with diagram.
What is ‘rusting’?
Answer the following question.
List two properties of alloys.
Give reason for the following:
A suspension of rust is basic in nature.
_______ is an alloy made from iron, carbon and chromium.
Pressure cooker : Anodizing : : Silver plated spoons : _______
Find the odd one out and give its explanation.
Find the odd one out and give its explanation.
Write the name.
Method used to prevent corrosion of copper.
Explain concept with example/explain with the help of a balanced equation.
Corrosion
Draw a neat labelled diagram.
Electroplating
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?
Galvanisation is a method of protecting iron from rusting by coating it with a thin layer of ____________.
Alloys are homogeneous mixtures of a metal with a metal or non-metal. Which among the following alloys contain non-metal as one of its constituents?
Generally, when metals are treated with mineral acids, hydrogen gas is liberated but when metals (except Mn and Mg), treated with HNO3, hydrogen is not liberated, why?
State whether the following statement is true or false:
Ships suffer a lot of damage though they are painted.
Explain the following:
Lime water turns milky on passing carbon dioxide gas into it.
Give an example of a chemical reaction for the following situation:
Sound is produced
Give scientific reasons.
Silver amalgam is used for filling dental cavities.
