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प्रश्न
Define corrosion.
Define the following term:
Corrosion
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उत्तर १
When the surface of a metal is attacked by air, moisture or any other substance around it, the metal is said to corrode and the phenomenon is known as corrosion.
उत्तर २
Corrosion is an electrochemical process in which a metal is oxidised to a metal oxide or another salt of the metal by losing electrons to oxygen or another electronegative element, forming a coating on the metal surface.
संबंधित प्रश्न
Why is photosynthesis considered an endothermic reaction?
Identify the component oxidised in the following reaction:
H2S + Cl2 → S + 2HCl
Fill in the following blanks with suitable words:
The addition of hydrogen to a substance is called ........ whereas removal of hydrogen is called .......
Fill in the blank
In redox reaction oxidation and reduction occur ............................
Define an oxidation reaction.
Define redox reaction.
Identify the substances that are oxidised and the substances that are reduced in the following reaction.
\[\ce{CuO_{(s)} + H2_{(g)} -> Cu_{(s)} + H2O_{(l)}}\]
The electron releasing tendency of zinc is ______ than that of copper.
Identify from the reaction the reactants that undergo oxidation and reduction.
Fe + S → FeS
Explain the following in term of gain or loss of oxygen with two examples.
Oxidation
In what respect does hydrogen differ from:
alkali metals
Give the general group study of hydrogen with reference to
reducing power
Describe briefly the ionic concept of oxidation and reduction. Give an equation to illustrate.
State, giving reason, whether the substances printed in bold letters have been oxidized or reduced.
H2S + Cl2→ 2HCl + S
State whether the following conversion is oxidation or reduction:
PbO2 + SO2→ PbSO4
Divide the following reactions into oxidation and reduction half-reaction:
Cl2 + 2Br- → Br2 + 2Cl-
Write the equation in the ionic form
CuSO4(aq) + Fe(s)→ FeSO4(aq) + Cu(s)
A metal oxide that is reduced by hydrogen is
Which of the following statements about hydrogen is incorrect?
Choose terms from the options given in brackets to complete this sentence.
When CuO reacts with hydrogen,………………… is reduced and ……………….is oxidized to ………………….
(CuO, H2, Cu, H2O)
Name:
a solid that is an oxidizing agent.
Complete and balance the following equation:
H2 + S → ___________
Complete and balance the following equation:
CuO +__________→ Cu +___________
State the condition and give balanced equation for the conversion of coke to water gas.
Explain the term redox reaction with an example involving the reaction of hydrogen sulphide with chlorine.
Select the correct answer from the symbol in the bracket.
The element, which like hydrogen is a strong reducing agent.
Balance the given chemical reaction as per the instructions below.
\[\ce{NaOH + H2SO4 -> Na2SO4 + H2O}\]
Oxidation means losing electrons then what is reduction?
Identify the following reactions as oxidation or reduction
- Na → Na+ + e
- Fe3+ + 2 e- → Fe+
Rusting of iron involves a chemical reaction which is a combination of:
Identify the reducing agent in the following reactions -
`"H"_2"O" + "F"_2 -> "HF" + "HOF"`
Identify the reducing agent in the following reactions
`"Fe"_2"O"_3 + 3"CO" -> 2"Fe" + 3"CO"_2`
Identify the reducing agent in the following reactions
`2"H"_2 + "O"_2 -> 2"H"_2"O"`
Identify the oxidising agent (oxidant) in the following reactions
`2"Mg" + "O"_2 -> 2"MgO"`
Identify the oxidising agent (oxidant) in the following reactions.
`"CuO" + "H"_2 -> "Cu" + "H"_2"O"`
Which among the following are physical or chemical change?
Burning of Liquefied Petroleum Gas (LPG)
Which among the following are physical or chemical change?
Heating of an iron rod to red hot
Which among the following are physical or chemical change?
Sublimation of solid ammonium chloride
During the reaction of some metals with dilute hydrochloric acid, following observations are made.
Silver metal does not show any change
Explain this observation giving suitable reason.
During the reaction of some metals with dilute hydrochloric acid, following observations are made.
Some bubbles of a gas are seen when lead (Pb) is reacted with the acid.
Explain this observation giving suitable reason.
Why do we store silver chloride in a dark coloured bottle?
On adding a drop of barium chloride solution to an aqueous solution of sodium sulphite, white precipitate is obtained :
- Write a balanced chemical equation for the reaction involved.
- What other name can be given to this precipitation reaction?
- On adding dilute hydrochloric acid to the reaction mixture, white precipitate disappears. Why?
Write a short note on oxidizing and reducing agents.
The tendency of atoms to have eight electrons in the outer shell is known as ______.
______ is a metal that has a high resistance to corrosion.
Choose the odd one out and write the reason:
Identify the following reactions as oxidation/reduction/redox reaction
2Mg +O2 → 2MgO
Find the oxidation number of the element in the following compound.
Ca in CaH2
When hydrogen gas is passed over black copper oxide, a reddish-coloured layer of copper is formed.
Answer the questions that follow based on this reaction.
- Write the equation.
- What type of reaction is it?
- Complete the blanks:
In this reaction, an oxygen atom goes away from CuO (copper oxide), which means that ______ of copper oxide takes place, whereas a hydrogen molecule takes up an oxygen atom and water (H2O) is formed, meaning ______ of hydrogen takes place.
Answer the questions based on the equation below:
\[\ce{CH3 - CH2 - OH ->[{[O]}][K2Cr2O7/H2SO4] CH3 - COOH}\]
- What type of reaction is it?
- What is the role of the chemical written on the arrow?
- Give one example of one such type of chemical as in answer (b).
It is recommended to use air tight containers for storing oil for a long time.
In the redox reaction:
MnO2 + 4HCl → MnCl2 + 2H2O + Cl2
A reddish brown metal used in electrical wires when powdered and heated strongly turns black. When hydrogen gas is passed over this black substance, it regains its original colour. Based on this information answer the following questions:
- Name the metal and the black substance formed.
- Write balanced chemical equations for the two reactions involved in the above information
State the change in colour observed in following case mentioning the reason:
Copper powder is strongly heated in air.
The metallic oxide which can be reduced by using common reducing agents is ______.
