Redox Reactions MCQ - Practice Questions & Answers

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Which of the following is a redox reaction?

$\mathrm{NaCl + KNO _{3} \rightarrow NaNO _{3}+ KCl}$

$\mathrm{CaC _{2} O _{4}+2 HCl \rightarrow CaCl _{2}+ H _{2} C _{2} O _{4}}$

$\mathrm{Mg ( OH )_{2}+2 NH _{4} Cl \rightarrow MgCl _{2}+2 NH _{4} OH}$

$\mathrm{Z n+2 A g C N \rightarrow 2 A g+Z n(C N)_{2}}$

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Statement I- corrosion is not an electrochemical phenomena
Statement II- Corrosion is defined as deterioration of a substance because of its rxn with environment

I is correct II is false

I is false II is true

Both I & II are true

Neither I nor II are true

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Concepts Covered - 1

Types of Redox Reactions

The different types of redox reactions are:

Decomposition Reaction
Combination Reaction
Displacement Reaction
Disproportionation Reactions

Decomposition Reaction
This is the reaction that involves the breakdown of a compound into different compounds. Some examples of this type of reaction are:

$2 \mathrm{H}_{2} \mathrm{O}(\mathrm{l}) \stackrel{\Delta}{\longrightarrow} 2 \mathrm{H}_{2}(\mathrm{g})+\mathrm{O}_{2}(\mathrm{g})$
$2 \mathrm{KClO}_{3}(\mathrm{s}) \stackrel{\Delta}{\longrightarrow} 2 \mathrm{KCl}(\mathrm{s})+3 \mathrm{O}_{2}(\mathrm{g})$

This must be noted here that all decomposition reactions are not redox reactions. For example, decomposition of calcium carbonate is not a redox reaction.
$\mathrm{CaCO}_{3}(\mathrm{s}) \stackrel{\Delta}{\longrightarrow} \mathrm{CaO}(\mathrm{s})+\mathrm{CO}_{2}(\mathrm{g})$

Combination Reaction
These types of reactions are the opposite of decomposition reaction and hence involve the combination of two species to form a single compound. Some examples include:

$\mathrm{C}(\mathrm{s})+\mathrm{O}_{2}(\mathrm{g}) \stackrel{\Delta}{\longrightarrow} \mathrm{CO}_{2}(\mathrm{g})$
$3Mg(s)+N_2(g)\rightarrow Mg_3N_2(s)$

Displacement Reaction
Displacement reactions, also known as replacement reactions, involve compounds and the replacement of elements. They occur as single and double replacement reactions. In other words, in theses type of reactions, an atom or an ion in a compound is substituted by another element.

Some examples include:

$\\\mathrm{Zn(s)+ CuSO_4(aq)\rightarrow ZnSO_4(aq)+Cu(s)(Metal\ displacement)} \\\mathrm{Na(s)+ H_2O(l)\rightarrow NaOH(aq)+H_2(g)(Non-Metal\ displacement)}$

Disproportionation Reactions

Disproportionation reactions are those reactions in which a single element in one oxidation state is simultaneously oxidized and reduced. Some examples include:

$\mathrm{P}_{4}(\mathrm{s})+3 \mathrm{OH^{-}}(\mathrm{aq})+3 \mathrm{H}_{2} \mathrm{O}(\mathrm{l}) \rightarrow \mathrm{PH}_{3}(\mathrm{g})+3 \mathrm{H}_{2} \mathrm{PO}_{2}^{-}$
$\begin{array}{r}{\mathrm{S}_{8}(\mathrm{s})+12 \mathrm{OH^-}(\mathrm{aq}) \rightarrow 4 \mathrm{S}^{2-}(\mathrm{aq})+2 \mathrm{S}_{2} \mathrm{O}_{3}^{2-}(\mathrm{aq})} \: {+6 \mathrm{H}_{2} \mathrm{O}(\mathrm{l})}\end{array}$

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Types of Redox Reactions

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Redox Reactions Current Topic

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Galvanic Cells

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Gibbs Free Energy of Reaction

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Types of Redox Reactions

Chemistry Part II Textbook for Class XI

Page No. : 270

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