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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
Define ‘redox reaction’. Give one example.
Identify in the following reaction (a) the substance oxidised, and (b) the substance reduced:
\[\ce{ZnO + C -> Zn + CO}\]
Identify the component oxidised in the following reaction:
\[\ce{H2S + Cl2 -> S + 2HCl}\]
The addition of hydrogen to a substance is called ______ whereas removal of hydrogen is called ______.
When a magnesium ribbon burns in air with a dazzling flame and forms a white ash, is magnesium oxidised or reduced? Why?
When a magnesium ribbon is heated, it burns in air to form magnesium oxide. Write a balanced chemical equation for this reaction. Name
- substance oxidised, and
- substance reduced.
In the context of redox reactions, the removal of hydrogen from a substance is known as ______.
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?
Identify from the reaction the reactants that undergo oxidation and reduction.
Fe + S → FeS
Give the general group study of hydrogen with reference to
reducing power
Compare hydrogen and halogens on the basis of:
reaction with oxygen
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:
Cu2+ + 2 e-→ Cu
Divide the following reactions into oxidation and reduction half-reaction:
Zn + Pb2+→ Pb + Zn 2+
Divide the following reactions into oxidation and reduction half-reaction:
Zn + Cu2+ → Cu + Zn 2+
For the reaction PbO + H2→ Pb + H2O, which of the following statements is wrong?
Name:
a substance that will reduce aqueous Iron(III)ions to iron(II)ions.
Complete and balance the following equation:
Zn +_________________→ZnCl2 + H2
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 reduction 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.
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.
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?
Heating of an iron rod to red hot
Which among the following are physical or chemical change?
Curding of milk
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.
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?
The tendency of atoms to have eight electrons in the outer shell is known as ______.
Choose the odd one out and write the reason:
Define oxidation number.
Find the oxidation number of the element in the following compound.
A1 in AlCl3
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).
State the change in colour observed in following case mentioning the reason:
Copper powder is strongly heated in air.
