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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
Why does the colour of copper sulphate solution change when an iron nail is dipped in it?
Define corrosion.
In the following reaction between lead sulphide and hydrogen peroxide:
PbS (s) + 4H2O2(aq) → PbSO4(s) + 4H2O(1)
(a) which substance is reduced?
(b) Which substance is oxidised?
When SO2 gas is passed through saturated solution of H2S, the following reaction occurs:
SO2 + 2H2S → 2H2O + 3S
In this reaction, which substance is oxidised and which one is reduced?
When a magnesium ribbon burns in air with a dazzling flame and forms a white ash, is magnesium oxidised or reduced? Why?
Give one example of an oxidation-reduction reaction which is also a combination reaction.
Define oxidation in terms of gain or loss of hydrogen with one example.
Define an oxidation 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.
\[\ce{CuO_{(s)} + H2_{(g)} -> Cu_{(s)} + H2O_{(l)}}\]
Electrolysis is a redox process. Explain.
How would you change a metal like Cu into its ions?
Identify from the reaction the reactants that undergo oxidation and reduction.
\[\ce{NiO + H2 -> Ni + H2O}\]
Explain the following in term of gain or loss of oxygen with two examples.
Oxidation
Explain the following in term of gain or loss of oxygen with two examples.
Reduction
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.
Cl2 + H2S → 2HCl + S
State whether the following conversion is oxidation or reduction:
K → K+ + e-
A metal oxide that is reduced by hydrogen is
For the reaction PbO + H2→ Pb + H2O, which of the following statements is wrong?
Name:
a substance that oxidizes concentrated HCl to chlorine.
Name:
a solid that is an oxidizing agent.
Complete and balance the following equation:
CuO +__________→ Cu +___________
State what is reducing agent. Give an example of oxidising agent in the gaseous, liquid, and solid form.
Give two tests for a reducing agent.
Explain the following reaction with their balanced chemical equation.
Hydrogen sulphide reacts with sulphur dioxide.
Find the oxidation number of the elements in the following compounds.
- C in CO2
- Mn in MnSO4
- N in HNO3
Oxidation is a process which involves ____________.
The process of reduction involves ____________.
Select the oxidising agent for the following reaction:
\[\ce{H2S + I2 -> 2HI + S}\]
In the reaction of iron with copper sulphate solution:
CuSO4 + Fe → Cu + FeSO4
Which option in the given table correctly represents the substance oxidized and the reducing agent?
| OPTION | Substance Oxidized | Reducing Agent |
| A | Fe | Fe |
| B | Fe | FeSO4 |
| C | Cu | Fe |
| D | CuSO4 | Fe |
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
`"CuSO"_4 + "Zn" -> "Cu" + "ZnSO"_4`
Which among the following are physical or chemical change?
Evaporation of petrol
Which among the following are physical or chemical change?
Burning of Liquefied Petroleum Gas (LPG)
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.
The temperature of the reaction mixture rises when aluminium (Al) is added.
Explain this observation giving suitable reason.
Why do we store silver chloride in a dark coloured bottle?
Zinc liberates hydrogen gas when reacted with dilute hydrochloric acid whereas copper does not. Explain why?
The sum of the oxidation number of all atoms in a compound is ______.
Choose the odd one out and write the reason:
Identify the following reactions as oxidation/reduction/redox reaction
Zn + CuSO4 → Cu + ZnSO4
Identify the following reactions as oxidation/reduction/redox reaction
CuO+H2 → Cu+H2O
What are reducing agents? Give examples.
What are redox reactions? Give examples.
Define oxidation number.
Find the oxidation number of the element in the following compound.
Mg in MgO
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.
State the change in colour observed in following case mentioning the reason:
Copper powder is strongly heated in air.
