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प्रश्न
What is meant by rust?
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उत्तर
Iron reacts with moist air to acquire a coating of a brown flaky substance called rust.
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संबंधित प्रश्न
Corrosion can be prevented by using ……………. solution.
A shiny brown-coloured element ‘X’ on heating in air becomes black in colour. Name the element ‘X’ and the black-colored compound formed.
The addition of hydrogen to a substance is called ______ whereas removal of hydrogen is called ______.
Give an example of an oxidation reaction.
Give one example of an oxidation-reduction reaction which is also a displacement reaction.
You are given the following chemical equation:
\[\ce{Mg_{(s)} + CuO_{(s)} -> MgO_{(s)} + Cu_{(s)}}\]
This equation represents:
Indicate which of the following statement is true and which is false:
The removal of hydrogen from a substance is called reduction.
Name the following:
The process in which oxygen is added or hydrogen is removed.
Define an oxidation reaction.
Define reduction.
Define redox reaction.
MULTIPLE CHOICE QUESTIONS
The process of adding oxygen to a substance is called
- oxidation.
- reduction.
- displacement.
- hydrogenation.
Identify the substances that are oxidised and the substances that are reduced in the following reaction.
\[\ce{CuO_{(s)} + H2_{(g)} -> Cu_{(s)} + H2O_{(l)}}\]
How would you change a metal like Cu into its ions?
Compare hydrogen and halogens on the basis of:
reaction with oxygen
Why zinc and aluminium are considered to have a unique nature. Give balanced equations to support your answer.
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.
Mg + 2HCl → MgCl2 + H2
State whether the following conversion is oxidation or reduction:
Cu2+ + 2 e-→ Cu
Write the equation in the ionic form
CuSO4(aq) + Fe(s)→ FeSO4(aq) + Cu(s)
Name:
an oxidizing agent that does not contain oxygen.
Name:
a substance that oxidizes concentrated HCl to chlorine.
Complete and balance the following equation:
H2 + S → ___________
Complete and balance the following equation:
Fe + H2O →___________+____________
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.
Identify the following reactions as oxidation or reduction
- Na → Na+ + e
- Fe3+ + 2 e- → Fe+
Find the oxidation number of the elements in the following compounds.
- C in CO2
- Mn in MnSO4
- N in HNO3
\[\ce{MnO2 + 4HCl -> + 2H2O + Cl2}\]
Identify the substance oxidized in the above equation.
Identify the reducing agent in the following reactions
`4"NH"_3 + 5"O"_2 -> 4"NO" + 6"H"_2"O"`
Identify the reducing agent in the following reactions
`"Fe"_2"O"_3 + 3"CO" -> 2"Fe" + 3"CO"_2`
Identify the oxidising agent (oxidant) in the following reactions
`"Pb"_3"O"_4 + 8"HCl" -> 3"PbCl"_2 + "Cl"_2 + 4"H"_2"O"`
Identify the oxidising agent (oxidant) in the following reactions
`2"Mg" + "O"_2 -> 2"MgO"`
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
A silver article generally turns black when kept in the open for a few days. The article when rubbed with toothpaste again starts shining.
- Why do silver articles turn black when kept in the open for a few days? Name the phenomenon involved.
- Name the black substance formed and give its chemical formula.
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.
Oxidizing agents are otherwise called ______.
The tarnishing of metals is an example of ______ reaction.
Choose the odd one out and write the reason:
Identify the following reactions as oxidation/reduction/redox reaction
Zn + CuSO4 → Cu + ZnSO4
What are redox reactions? Give examples.
What is rancidity?
Define oxidation number.
Find the oxidation number of the element in the following compound.
Ca in CaH2
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).
In the redox reaction:
MnO2 + 4HCl → MnCl2 + 2H2O + Cl2
State whether the given chemical reaction is a redox reaction or not. Justify your answer.
\[\ce{MnO_2 + 4HCl->MnCl_2 +2H_2O + Cl_2}\]
The oxidizing agent in the equation \[\ce{S + 2H2SO4 -> 3SO2 + 2H2O}\] is ______.
The metallic oxide which can be reduced by using common reducing agents is ______.
