Redox Reactions · JEE Main previous year questions

2023 16 questions

1. Q692023 · 13 Apr 2023 · Shift 2

   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
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   Answer: B

2. Q632023 · 11 Apr 2023 · Shift 2

   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
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   Answer: A

3. Q872023 · 8 Apr 2023 · Shift 2· Numerical answer

   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 ____.

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   Answer: 10

4. Q652023 · 6 Apr 2023 · Shift 1

   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
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   Answer: A

5. Q722023 · 6 Apr 2023 · Shift 1

   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 ${\text{Ce}}^{4+}$
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   Answer: B

6. Q892023 · 6 Apr 2023 · Shift 1· Numerical answer

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

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   Answer: 6

7. Q632023 · 1 Feb 2023 · Shift 1

   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
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   Answer: A

8. Q862023 · 1 Feb 2023 · Shift 1· Numerical answer

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

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   Answer: 12

9. Q792023 · 31 Jan 2023 · Shift 1

   ${\mathrm{H}}_2{\mathrm{O}}_2$ 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.$2\mathrm{NaOCl}+{\mathrm{H}}_2{\mathrm{O}}_2\to 2\mathrm{NaCl}+{\mathrm{H}}_2\mathrm{O}+{\mathrm{O}}_2$
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   Answer: D

10. Q862023 · 31 Jan 2023 · Shift 1· Numerical answer

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

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    Answer: 4

11. Q872023 · 31 Jan 2023 · Shift 2· Numerical answer

    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)

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    Answer: 59

12. Q672023 · 29 Jan 2023 · Shift 2

    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)
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    Answer: D

13. Q712023 · 25 Jan 2023 · Shift 2

    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
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    Answer: C

14. Q722023 · 25 Jan 2023 · Shift 2

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

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

15. Q682023 · 24 Jan 2023 · Shift 2

    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
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    Answer: A

16. Q752023 · 24 Jan 2023 · Shift 2

    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.$2F{\mathrm{e}}^{2+}+{\mathrm{H}}_2{\mathrm{O}}_2\to 2F{\mathrm{e}}^{3+}+2O{\mathrm{H}}^{-}$
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    Answer: B