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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
Identify the substances that are oxidised and the substances that are reduced in the following reaction.
\[\ce{4Na(s) + O2(g) -> 2Na2O(s)}\]
What are anti-oxidants? Why are they added to fat and oil containing foods?
What is an oxidation reaction? Identify in the following reaction (i) the substance oxidised, and (ii) the substance reduced:
ZnO + C → Zn + CO
Identify the component oxidised in the following reaction:
H2S + Cl2 → S + 2HCl
When a magnesium ribbon burns in air with a dazzling flame and forms a white ash, is magnesium oxidised or reduced? Why?
In the reaction represented by the equation:
MnO2 + 4HCl → MnCl2 + 2H2O + Cl2
(i) name the substance oxidised.
(ii) name the oxidising agent.
(iii) name the substance reduced.
(iv) name the reducing agent.
Is oxidation an exothermic or an endothermic reaction?
Explain reduction in terms of gain or loss of oxygen with one example.
In the context of redox reactions, the removal of hydrogen from a substance is known as:
(a) oxidation
(b) dehydration
(c) reduction
(d) dehydrogenation
The process of respiration is:
(a) an oxidation reaction which is endothermic
(b) a reduction reaction which is exothermic
(c) a combination reaction which is endothermic
(d) an oxidation reaction which is exothermic
You are given the following chemical equation:
Mg (s) + CuO (s) → MgO (s) + Cu (s)
This equation represents:
(a) decomposition reaction as well as displacement reaction
(b) combination reaction as well as double displacement reaction
(c) redox reaction as well as displacement reaction
(d) double displacement reaction as well as redox reaction
Indicate which of the following statement is true and which is false:
The removal of hydrogen from a substance is called reduction.
Define an oxidation reaction.
Identify the substances that are oxidised and the substances that are reduced in the following reaction.
\[\ce{CuO_{(s)} + H2_{(g)} -> Cu_{(s)} + H2O_{(l)}}\]
Identify from the reaction the reactants that undergo oxidation and reduction.
Fe + S → FeS
Identify from the reaction the reactants that undergo oxidation and reduction.
2Mg + O2 → 2MgO
Identify from the reaction the reactants that undergo oxidation and reduction.
\[\ce{NiO + H2 -> Ni + H2O}\]
Compare hydrogen and halogens on the basis of:
reaction with oxygen
Why this reaction is considered a reversible reaction?
State whether the following conversion is oxidation or reduction:
PbO2 + SO2→ PbSO4
Divide the following reactions into oxidation and reduction half-reaction:
Zn + Cu2+ → Cu + Zn 2+
Write the equation in the ionic form
CuSO4(aq) + Fe(s)→ FeSO4(aq) + Cu(s)
Divide the above equation into oxidation and reduction half-reactions.
A metal oxide that is reduced by hydrogen is
For the reaction PbO + H2→ Pb + H2O, which of the following statements is wrong?
Complete and balance the following equation:
CuO +__________→ Cu +___________
Complete and balance the following equation:
\[\ce{K + H2O -> }\]________+ ________
With reference to oxidation & reduction reaction – complete the statement given by filling in the blanks with only the words (a) Addition (b) Removal.
‘Oxidation is a chemical reaction involving ____ of oxygen to a substance or ____ of hydrogen from a substance. Reduction on the otherhand involves ____ of hydrogen to a substance or ____ of oxygen from a substance.
Explain the term oxidation in term of addition and removal of oxygen/hydrogen with a suitable example.
State what is reducing agent. Give an example of oxidising agent in the gaseous, liquid, and solid form.
Oxidising agents are also called as ______ because they remove electrons form other substances.
The process of reduction involves ____________.
\[\ce{MnO2 + 4HCl -> + 2H2O + Cl2}\]
Identify the substance oxidized in the above equation.
When Ag is exposed to air it gets a black coating of ____________.
Identify the oxidising agent (oxidant) in the following reactions
`"CuSO"_4 + "Zn" -> "Cu" + "ZnSO"_4`
Grapes hanging on the plant do not ferment but after being plucked from the plant can be fermented. Under what conditions do these grapes ferment? Is it a chemical or a physical change?
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
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.
The reaction of sodium metal is found to be highly explosive
Explain this observation giving suitable reason.
Zinc liberates hydrogen gas when reacted with dilute hydrochloric acid whereas copper does not. Explain why?
You are provided with two containers made up of copper and aluminium. You are also provided with solutions of dilute HCl, dilute HNO3, ZnCl2 and water. In which of the above containers, can these solutions be kept?
Write a short note on oxidizing and reducing agents.
The formation of brown colour on the freshly unit surface of vegetables and fruits is because ______ of organic compounds present in them.
The tarnishing of metals is due to the formation of ______.
The tarnishing of metals is an example of ______ reaction.
What is rancidity?
Define oxidation number.
Find the oxidation number of the element in the following compound.
Ca in CaH2
Find the oxidation number of the element in the following compound.
Mg in MgO
Find the oxidation number of the element in the following compound.
N in NH3
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.
It is recommended to use air tight containers for storing oil for a long time.
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.
