Tag: classical idea of redox reactions

Questions Related to classical idea of redox reactions

Minerals associated with  redox reactions are

bio-chemistry biological oxidation classical idea of redox reactions oxidation reduction redox reaction

  1. Na, Cu

  2. N, Cu

  3. Fe, Cu

  4. Ca, Fe

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Correct Option: C

Which of the following is a redox reaction?

bio-chemistry biological oxidation classical idea of redox reactions oxidation reduction redox reaction

  1. $C{ a }CO _{ 3 }\quad \rightarrow \quad { { C }{ a }O+{ CO } _{ 2 } }$

  2. $H _{ 2 }+Cl _{ 2 }\quad \rightarrow \quad 2HCl$

  3. ${ C }{ a }O+2HCl\quad \rightarrow \quad { C }{ a }{ Cl } _{ 2 }+{ H } _{ 2 }O$

  4. ${ N }{ a }OH+HCl\quad \rightarrow \quad { N }{ a }{ Cl }+{ H } _{ 2 }O$

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Correct Option: A

Which reaction is not a redox reaction?

bio-chemistry biological oxidation classical idea of redox reactions oxidation reduction redox reaction

  1. $Mg+2HNO _3\rightarrow Mg(NO _3) _2+H _2$

  2. $2Mg(NO _3) _2\rightarrow 2MgO+4NO _2+O _2$

  3. $SO _2+NO _2\rightarrow SO _3+NO$

  4. $SO _3+H _2O\rightarrow H _2SO _4$

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Correct Option: C

How many moles of electrons are involved in the reduction of one mole of $MnO^- _4$ ion in alkaline medium to $MnO^- _3$?

bio-chemistry biological oxidation classical idea of redox reactions oxidation reduction redox reaction

  1. $2$

  2. $1$

  3. $3$

  4. $4$

Show answer
Correct Option: A
Explanation:
Reaction takes place as follows:
$Mn{ O } _{ 4 }^{ - }+{ H } _{ 2 }O+{ 2e }^{ - }\rightarrow Mn{ O } _{ 3 }^{ - }+2O{ H }^{ - }$
So, 2 electrons are involved in reduction of 1 mole of ${MnO} _4^{-}$ ion in alkaline medium to ${MnO} _3^{-}$.

In acid medium, the standard reduction potential of $NO$ converted to ${ N } _{ 2 }O$ is $1.59 V$. Its standard potential in alkaline medium would be:

bio-chemistry biological oxidation classical idea of redox reactions oxidation reduction redox reaction

  1. $-1.59 V$

  2. $-0.764 V$

  3. $0.764 V$

  4. $0.062 V$

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Correct Option: C
Explanation:

$NO \longrightarrow N _2O$      $E^o= 1.59V$

The reaction in acidic medium,
$2NO+2H^+ \longrightarrow N _2O+H _2O$;   $E^o=1.59$
In basic medium,
$2NO+H _2O \longrightarrow N _2O+2OH^-$;   Let $E^o=x$
Now, in alkaline medium,
$H _2O \rightleftharpoons H^++OH^-$
$\Rightarrow K=10^{-14}$
or, $2H _2O \rightleftharpoons 2H^++2OH^-$,   $K= 10^{-28}$
We know, $E^o= \cfrac {0.059}{n}\log K$
$=\cfrac {0.059}{2}\log 10^{-28}= 0.826$
For standard potential,
$E^o _{acidic}+E^o _{basic}=E^o _{cell}$
$\Rightarrow 1.59+x= 0.826$
$\Rightarrow x= 0.764$

A solution contains ${Fe}^{+2},{Fe}^{+3}$ and ${I}^{-}$ ions. This solution was treated with iodine at ${35}^{o}C$. Then the favourable redox reaction is: 

(Given that ${ E } _{ { Fe }^{ +3 }/{ Fe }^{ +2 } }^{ o }=+0.77V;\quad { E } _{ { I } _{ 2 }/{ I }^{ - } }^{ o }=0.536V$)

bio-chemistry biological oxidation classical idea of redox reactions oxidation reduction redox reaction

  1. ${I} _{2}$ will be reduced to ${I}^{-}$

  2. there will be no redox reaction

  3. ${I}^{-}$ will be oxidised to ${I} _{2}$

  4. ${Fe}^{+}$ will be oxidised to ${Fe}^{+3}$

Show answer
Correct Option: A
Explanation:

${ 2I }^{ - }\rightarrow { I } _{ 2 }+{ 2e }^{ - }(oxidation\quad half-reaction)$

${ E } _{ Oxidation }^{ 0 }=-0.536V$

${ Fe }^{ 3+ }+e^{ - }\rightarrow { Fe }^{ 2+ }(reduction\quad half-reaction)$

$E^{ 0 } _{ Reduction }=-0.77V$
----------------------------------------------------------------------------------------------------------------------
${ 2Fe }^{ 3+ }+{ 2I }^{ - }\rightarrow { 2Fe }^{ 2+ }+{ I } _{ 2 }$

$E^{ 0 }={ E } _{ oxidation }^{ 0 }+E _{ Reduction }^{ 0 },+ve$

Hence the reaction will take place.

${ 2I }^{ - }\rightarrow { I } _{ 2 }+{ 2e }^{ - }(oxidation\quad half-reaction)$

${ E }^{ 0 } _{ Oxidation }=-0.536V$

${ Fe }^{ 3+ }+{ e }^{ - }\rightarrow { Fe }^{ 2+ }(reduction\quad half-reaction)$

$E _{ Reduction }^{ 0 }=-0.77V$
------------------------------------------------------------------------------------------------------------------------
$2Fe^{ 3+ }+{ 2I }^{ - }\rightarrow { 2Fe }^{ 2+ }+{ I } _{ 2 };$

${ E }^{ 0 }={ E } _{ oxidation }^{ 0 }+{ E } _{ reduction }^{ 0 };+ve$

$HOCl(aq)$ is the molecule that kills bacteria wen chlorine is added to water. 
The following reaction produces this molecule
${Cl} _{2}(g)+{H} _{2}O(l)\rightleftharpoons HOCl(aq)+{H}^{+}(aq)+{Cl}^{-}(aq)$
Which statement about this reaction is correct?

bio-chemistry biological oxidation classical idea of redox reactions oxidation reduction redox reaction

  1. Chlorine is both oxidised and reduced

  2. Chlorine is oxidised but not reduced

  3. Hydrogen is both oxidised and reduced

  4. Hydrogen is oxidised but not reduced

Show answer
Correct Option: A
Explanation:

Oxidation and reduction are two types of chemical reactions that often work together. Oxidation and reduction reactions involve an exchange of electrons between reactants.

  • Reduction and oxidation occur simultaneously in a type of chemical reaction called a reduction-oxidation or redox reaction.
  • Oxidation Involves Loss of electrons
  • Reduction Involves Gain of electrons.
As we can see the above case with the chlorine .
hence chlorine is both oxidised and reduced

Which of the following reaction is non-redox?

bio-chemistry biological oxidation classical idea of redox reactions oxidation reduction redox reaction

  1. $2NaNO _{3}\rightarrow 2NaNO _{2}+O _{2}$

  2. $CaO+SiO _{2}\rightarrow CaSiO _{3}$

  3. $Fe+H _{2}SO _{4}\rightarrow FeSO _{4}+H _{2}$

  4. $4Ag+8CN^{-}+O _{2}+2H _{2}O\rightarrow 4[Ag(CN) _{2}]^{-}+4OH^{-}$

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Correct Option: B

A redox reaction is

bio-chemistry biological oxidation classical idea of redox reactions oxidation reduction redox reaction

  1. exothermic

  2. endothermic

  3. neither exothermic nor endothermic

  4. either exothermic or endothermic

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Correct Option: D

One gas bleaches the colour of flowers by reduction while the other gas by oxidation. The two gases are, respectively:

bio-chemistry biological oxidation classical idea of redox reactions oxidation reduction redox reaction

  1. $CO$ & $Cl _{2}$

  2. $H _{2}S$ & $Br _{2}$

  3. $SO _{2}$ & $Cl _{2}$

  4. $NH _{3}$ & $SO _{3}$

Show answer
Correct Option: C
Explanation:
Sulphur dioxide and chlorine gas are the two gases that bleach the colour of flower by oxidation and reduction.

Chlorine reacts with water and produces a single oxygen atom also called nascent oxygen. This nascent oxygen when combines with any colour make it colourless.

$Cl _{2}+H _{2}O\rightarrow 2HCl+(O)$ (O is oxidizing)

Sulphur dioxide when reacts with coloured substances it releases oxygen from the substance resulting in loss of colour.

$SO _{2}+2H _{2}O\rightarrow H _{2}SO _{4}+2(H)$  (H is reducing)

Hence, the correct option is $C$