Redox Reactions · JEE Main previous year questions

Given below are two statements: Statement I : ${\mathrm{S}}_8$ solid undergoes disproportionation reaction under alkaline conditions to form ${\mathrm{S}}^{2-}$ and ${\mathrm{S}}_2{\mathrm{O}}_3{}^{2-}$. Statement II : $\mathrm{Cl}{\mathrm{O}}_4^{-}$ can undergo disproportionation reaction under acidic condition. In the light of the above statements, choose the most appropriate answer from the options given below :

1. A.Statement I is correct but statement II is incorrect
2. B.Both statement I and statement II are incorrect
3. C.Statement I is incorrect but statement II is correct
4. D.Both statement I and statement II are correct

Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A) : There is a considerable increase in covalent radius from $\mathrm{N}$ to $\mathrm{P}$. However from As to Bi only a small increase in covalent radius is observed. Reason (R) : Covalent and ionic radii in a particular oxidation state increases down the group. In the light of the above statements, choose the most appropriate answer from the options given below:

1. A.(A) is false but (R) is true
2. B.Both (A) and (R) are true and (R) is the correct explanation of (A)
3. C.Both (A) and (R) are true but (R) is not the correct explanation of (A)
4. D.(A) is true but (R) is false

Chlorine undergoes disproportionation in alkaline medium as shown below : $$\mathrm{aC}{\mathrm{l}}_{2(\mathrm{g})}+\mathrm{bO}{\mathrm{H}}_{(\mathrm{aq})}^{-}\to \mathrm{cCl}{\mathrm{O}}_{(\mathrm{aq})}^{-}+\mathrm{dC}{\mathrm{l}}_{(\mathrm{aq})}^{-}+\mathrm{e}{\mathrm{H}}_2{\mathrm{O}}_{(\mathrm{l})}$$ The values of $a,b,c$ and $d$ in a balanced redox reaction are respectively :

1. A.$3,4,4$ and $2$
2. B.$1,2,1$ and $1$
3. C.$2,4,1$ and $3$
4. D.$2,2,1$ and $3$

Which of the following acts as a strong reducing agent? (Atomic number: $\mathrm{Ce}=58,\mathrm{Eu}=63,\mathrm{Gd}=64,\mathrm{Lu}=71$)

1. A.${\mathrm{Eu}}^{2+}$
2. B.${\mathrm{Gd}}^{3+}$
3. C.${\mathrm{Lu}}^{3+}$
4. D.${\mathrm{Ce}}^{4+}$

Element not showing variable oxidation state is :

1. A.Bromine
2. B.Iodine
3. C.Chlorine
4. D.Fluorine

From the given list, the number of compounds with +4 oxidation state of Sulphur _______. ${\text{SO}}_3,{\text{H}}_2{\text{SO}}_3,{\text{SOCl}}_2,{\text{SF}}_4,{\text{BaSO}}_4,{\text{H}}_2{\text{S}}_2{\text{O}}_7$

Given below are two statements : Statement (I) : Oxygen being the first member of group 16 exhibits only -2 oxidation state. Statement (II) : Down the group 16 stability of +4 oxidation state decreases and +6 oxidation state increases. In the light of the above statements, choose the most appropriate answer from the options given below :

1. A.Statement I is correct but Statement II is incorrect
2. B.Both Statement I and Statement II are incorrect
3. C.Statement I is incorrect but Statement II is correct
4. D.Both Statement I and Statement II are correct

Which of the following cannot function as an oxidising agent?

1. A.${\text{SO}}_4^{2-}$
2. B.${\text{MnO}}_4^{-}$
3. C.${\text{N}}^{3-}$
4. D.${\text{BrO}}_3^{-}$

The covalency and oxidation state respectively of boron in $[{\mathrm{BF}}_4{]}^{-}$, are :

1. A.3 and 4
2. B.4 and 3
3. C.4 and 4
4. D.3 and 5

Given below are two statements, one is labelled as Assertion A and the other is labelled as Reason R. Assertion A : $[\mathrm{CoCl}(\mathrm{N}{\mathrm{H}}_3{)}_5{]}^{2+}$ absorbs at lower wavelength of light with respect to $[\mathrm{Co}(\mathrm{N}{\mathrm{H}}_3{)}_5({\mathrm{H}}_2\mathrm{O}){]}^{3+}$ Reason R : It is because the wavelength of the light absorbed depends on the oxidation state of the metal ion. In the light of the above statements, choose the correct answer from the options given below:

1. A.A is false but R is true
2. B.Both A and R are true but R is NOT the correct explanation of A
3. C.Both A and R are true and R is the correct explanation of A
4. D.A is true but R is false

The sum of oxidation state of the metals in $\mathrm{Fe}(\mathrm{CO}{)}_5$, $\mathrm{V}{\mathrm{O}}^{2+}$ and $\mathrm{W}{\mathrm{O}}_3$ is ____.

Which of the following options are correct for the reaction $$2[\text{Au}(\text{CN}{)}_2{]}^{-}(\text{aq})+\text{Zn}(\text{s})\to 2\text{Au}(\text{s})+[\text{Zn}(\text{CN}{)}_4{]}^{2-}(\text{aq})$$ A. Redox reaction B. Displacement reaction C. Decomposition reaction D. Combination reaction Choose the correct answer from the options given below:

1. A.A and B only
2. B.C and D only
3. C.A only
4. D.A and D only

Strong reducing and oxidizing agents among the following, respectively, are :

1. A.${\text{Ce}}^{4+}$ and ${\text{Eu}}^{2+}$
2. B.${\text{Eu}}^{2+}$ and ${\text{Ce}}^{4+}$
3. C.${\text{Ce}}^{4+}$ and ${\text{Tb}}^{4+}$
4. D.${\text{Ce}}^{3+}$ and ${\text{Ce}}^{4+}$

In ammonium - phosphomolybdate, the oxidation state of Mo is + ___________

Highest oxidation state of Mn is exhibited in ${\text{Mn}}_2{\text{O}}_7$. The correct statements about ${\text{Mn}}_2{\text{O}}_7$ are (A) Mn is tetrahedrally surrounded by oxygen atoms. (B) Mn is octahedrally surrounded by oxygen atoms. (C) Contains Mn-O-Mn bridge. (D) Contains Mn-Mn bond. Choose the correct answer from the options given below :

1. A.A and C only
2. B.A and D only
3. C.B and C only
4. D.B and D only

Sum of oxidation states of bromine in bromic acid and perbromic acid is ___________.

${\mathrm{H}}_2{\mathrm{O}}_2$ acts as a reducing agent in :

1. A.${\mathrm{Mn}}^{2+}+2{\mathrm{H}}_2{\mathrm{O}}_2\to {\mathrm{MnO}}_2+2{\mathrm{H}}_2\mathrm{O}$
2. B.$2{\mathrm{Fe}}^{2+}+2{\mathrm{H}}^{+}+{\mathrm{H}}_2{\mathrm{O}}_2\to 2{\mathrm{Fe}}^{3+}+2{\mathrm{H}}_2\mathrm{O}$
3. C.${\mathrm{Na}}_2\mathrm{S}+4{\mathrm{H}}_2{\mathrm{O}}_2\to {\mathrm{Na}}_2{\mathrm{SO}}_4+4{\mathrm{H}}_2\mathrm{O}$
4. D.$2\mathrm{NaOCl}+{\mathrm{H}}_2{\mathrm{O}}_2\to 2\mathrm{NaCl}+{\mathrm{H}}_2\mathrm{O}+{\mathrm{O}}_2$

The oxidation state of phosphorus in hypophosphoric acid is + _____________.

A sample of a metal oxide has formula ${\mathrm{M}}_{0.83}{\mathrm{O}}_{1.00}$. The metal M can exist in two oxidation states $+2$ and $+3$. In the sample of ${\mathrm{M}}_{0.83}{\mathrm{O}}_{1.00}$, the percentage of metal ions existing in $+2$ oxidation state is ___________ $\%$. (nearest integer)

The set of correct statements is : (i) Manganese exhibits +7 oxidation state in its oxide. (ii) Ruthenium and Osmium exhibit +8 oxidation state in their oxides. (iii) Sc shows +4 oxidation state which is oxidizing in nature. (iv) Cr shows oxidising nature in +6 oxidation state.

1. A.(ii), (iii) and (iv)
2. B.(ii) and (iii)
3. C.(i) and (iii)
4. D.(i), (ii) and (iv)

Potassium dichromate acts as a strong oxidizing agent in acidic solution. During this process, the oxidation state changes from :

1. A.+ 2 to + 1
2. B.+ 6 to + 2
3. C.+ 6 to + 3
4. D.+ 3 to + 1

Which one among the following metals is the weakest reducing agent?

1. A.K
2. B.Na
3. C.Li
4. D.Rb

Which one amongst the following are good oxidizing agents? A. $\mathrm{S}{\mathrm{m}}^{2+}$ B. $\mathrm{C}{\mathrm{e}}^{2+}$ C. $\mathrm{C}{\mathrm{e}}^{4+}$ D. $\mathrm{T}{\mathrm{b}}^{4+}$ Choose the most appropriate answer from the options given below :

1. A.C and D only
2. B.A and B only
3. C.D only
4. D.C only

In which of the following reactions the hydrogen peroxide acts as a reducing agent?

1. A.$\mathrm{M}{\mathrm{n}}^{2+}+{\mathrm{H}}_2{\mathrm{O}}_2\to \mathrm{M}{\mathrm{n}}^{4+}+2O{\mathrm{H}}^{-}$
2. B.$\mathrm{HOCl}+{\mathrm{H}}_2{\mathrm{O}}_2\to {\mathrm{H}}_3{\mathrm{O}}^{+}+\mathrm{C}{\mathrm{l}}^{-}+{\mathrm{O}}_2$
3. C.$\mathrm{PbS}+4{\mathrm{H}}_2{\mathrm{O}}_2\to \mathrm{PbS}{\mathrm{O}}_4+4{\mathrm{H}}_2\mathrm{O}$
4. D.$2F{\mathrm{e}}^{2+}+{\mathrm{H}}_2{\mathrm{O}}_2\to 2F{\mathrm{e}}^{3+}+2O{\mathrm{H}}^{-}$

In neutral or faintly alkaline medium, $\mathrm{KMn}{\mathrm{O}}_4$ being a powerful oxidant can oxidize, thiosulphate almost quantitatively, to sulphate. In this reaction overall change in oxidation state of manganese will be :

1. A.5
2. B.1
3. C.0
4. D.3