Tag: oxidation reduction

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Questions Related to oxidation reduction

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

Which of the following is a 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. ${ N }{ a }OH+HCl\quad \rightarrow \quad { N }{ a }{ Cl }+{ H } _{ 2 }O$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A redox reaction involves the change in oxidation states of atoms. In option B, elemental hydrogen and chlorine react to form hydrogen chloride, where hydrogen is oxidized from 0 to +1 and chlorine is reduced from 0 to -1. The other options represent thermal decomposition or double displacement reactions without changes in oxidation numbers.

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

Which reaction is not a 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. $SO _3+H _2O\rightarrow H _2SO _4$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

A redox reaction is characterized by a change in the oxidation states of the reacting species. Option D is a combination reaction between sulfur trioxide and water to form sulfuric acid, where sulfur remains in the +6 oxidation state, oxygen remains in the -2 state, and hydrogen remains in the +1 state throughout. The other three options involve changes in oxidation states, making them redox processes.

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

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

  1. $2$
  2. $1$
  3. $3$
  4. $4$
Reveal answer Fill a bubble to check yourself
A Correct answer
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 ${MnO} _3^{-}$.
Multiple choice bio-chemistry biological oxidation classical idea of redox reactions oxidation reduction redox reaction

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:

  1. $-1.59 V$
  2. $-0.764 V$
  3. $0.764 V$
  4. $0.062 V$
Reveal answer Fill a bubble to check yourself
C Correct answer
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,
$E^o _{acidic}+E^o _{basic}=E^o _{cell}$
$\Rightarrow 1.59+x= 0.826$
$\Rightarrow x= 0.764$

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

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

  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 ${Fe}^{+3}$
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

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

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

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

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

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

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

$HOCl(aq)$ 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?

  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
Reveal answer Fill a bubble to check yourself
A Correct answer
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

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

Which of the following reaction is non-redox?

  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. $4Ag+8CN^{-}+O _{2}+2H _{2}O\rightarrow 4[Ag(CN) _{2}]^{-}+4OH^{-}$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In option B, CaO + SiO2 -> CaSiO3, the oxidation states of Ca (+2), O (-2), and Si (+4) remain unchanged. This is an acid-base reaction, not a redox reaction.

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

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

  1. $CO$ & $Cl _{2}$
  2. $H _{2}S$ & $Br _{2}$
  3. $SO _{2}$ & $Cl _{2}$
  4. $NH _{3}$ & $SO _{3}$
Reveal answer Fill a bubble to check yourself
C Correct answer
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 $C$