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NEET • CHEMISTRY • REDOX REACTIONS

Redox reactions practice · Mixed difficulty

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61 Easy

61 of 184

Analyzing +4 | -1

when

{\mathbf{K}_\mathbf{2}}\mathbf{C}{\mathbf{r}_\mathbf{2}}{\mathbf{O}_\mathbf{7}}

is converted to

{\mathbf{K}_\mathbf{2}}\mathbf{Cr}{\mathbf{O}_\mathbf{4}}

, the change in the oxidation of chromium is

View answer and explanation

Correct option: A

Option A (0) is correct because the oxidation state of chromium remains +6 in both K2Cr2O7 and K2CrO4.

62 Medium

62 of 184

Application +4 | -1

In which of the following

N

has lowest oxidation number?

View answer and explanation

Correct option: C

{\mathrm{N}_2}\mathrm{O}

The correct answer is C (N2O) because the oxidation number of N in N2O is +1, which is the lowest among the given options.

63 Medium

63 of 184

Remembering +4 | -1

Which of the following metals do not react with steam?

View answer and explanation

Correct option: C

Tin and cadmium

Option C (Tin and cadmium) is correct because tin and cadmium are less reactive and do not react with steam under normal conditions.

64 Medium

64 of 184

Remembering +4 | -1

An element if present in the free or the uncombined state, its each atom bears an oxidation number of

View answer and explanation

Correct option: D

zero

Option D (zero) is correct because the oxidation number of an element in its free or uncombined state is always zero.

65 Medium

65 of 184

Understanding +4 | -1

WI ich acts as a reducing agent?

View answer and explanation

Correct option: D

{\left( {\mathrm{COOH}} \right)_2}

Option D (

{\left( {\mathrm{COOH}} \right)_2}

) is correct because oxalic acid can be oxidized, thus acting as a reducing agent.

66 Hard

66 of 184

Application +4 | -1

The oxidation number of N and Cl in

\mathrm{NOCl}{\mathrm{O}_4}

respectively are

View answer and explanation

Correct option: B

+ 3\,and + 7

Option B (

+ 3\,and + 7

) is correct because the oxidation number of N is +3 and Cl is +7 in

\mathrm{NOCl}{\mathrm{O}_4}

67 Medium

67 of 184

Analyzing +4 | -1

Which of the following is redox reaction?

View answer and explanation

Correct option: D

\mathrm{SnC}{\mathrm{l}_2}\mathrm{ + HgC}{\mathrm{l}_2} \to \mathrm{SnC}{\mathrm{l}_4} + \mathrm{Hg}

Option D (

\mathrm{SnC}{\mathrm{l}_2}\mathrm{ + HgC}{\mathrm{l}_2} \to \mathrm{SnC}{\mathrm{l}_4} + \mathrm{Hg}

) is correct because the oxidation state of Sn increases and Hg decreases, indicating a redox reaction.

68 Easy

68 of 184

Remembering +4 | -1

Which of the following shows highest ox, no. in combined state?

View answer and explanation

Correct option: C

Both (a) and (b)

Option C (Both (a) and (b)) is correct because both Osmium (Os) and Ruthenium (Ru) can exhibit a maximum oxidation state of +8 in their combined states.

69 Easy

69 of 184

Analyzing +4 | -1

Sulphur Containing species that cannot be a reducing agent is

View answer and explanation

Correct option: C

{H_2}S{O_4}

Option C (H2SO4) is correct because sulfur is already in its highest oxidation state (+6) and cannot be further oxidized.

70 Easy

70 of 184

Understanding +4 | -1

In the preparation of chlorine from

\mathrm{HCl},\mathrm{Mn}{\mathrm{O}_2}

acts as :

View answer and explanation

Correct option: B

oxidising agent

Option B (oxidising agent) is correct because MnO2 accepts electrons from HCl, causing HCl to be oxidized and itself to be reduced.

71 Medium

71 of 184

Application +4 | -1

The number of mole of

\mathrm{KMn}{\mathrm{O}_4}

that will be needed to react completely with one mole of ferrous oxalate in acidic solution is :

View answer and explanation

Correct option: A

\frac{3}{5}

Option A (

\frac{3}{5}

) is correct because the balanced redox reaction requires 3 moles of KMnO4 to react completely with 5 moles of ferrous oxalate.

72 Easy

72 of 184

Remembering +4 | -1

The equivalent weight of a reductant or an oxidant is given by :

View answer and explanation

Correct option: A

\mathrm{Eq}\mathrm{.wt}\mathrm{.} = \frac{{\mathrm{mol}\mathrm{.weight\,\, of\,\, reductant\,\, or\,\, oxidant}}}{{\begin{array}{cccccccccccccccccccc} {\mathrm{no}\mathrm{.of\,\, electrons\,\, lost\,\, or\,\, gained \,\,by}}\\ {1{\rm{molecule\,\, of\,\, reductant\,\, or\,\, oxida

Option A is correct because the equivalent weight is the molecular weight divided by the number of electrons lost or gained per molecule.

73 Hard

73 of 184

Analyzing +4 | -1

In acid medium Zn reduces nitrate ion to

\mathrm{NH}_4^ +

ion according to the reaction

\mathrm{Zn} + \mathrm{N}{\mathrm{O}_3}

\mathrm{Z}{\mathrm{n}^{2 + }} + \mathrm{NH}_4^ + + {\mathrm{H}_2}\mathrm{O}

(unbalanced).How many moles of

HCl

are required to teduce half a mole of

\mathrm{NaN}{\mathrm{O}_3}

completely? Assume the availability of sufficient Zn.

View answer and explanation

Correct option: A

Option A (5) is correct because the balanced equation shows that 10 moles of HCl are required to reduce 1 mole of NaNO3 to NH4+, so 5 moles are needed for half a mole.

74 Hard

74 of 184

Understanding +4 | -1

Why the displacement reactions of chlorine, bromine and iodine using fluorine are not generally carried out in aqueous solution?

View answer and explanation

Correct option: B

Fluorine being very reactive attacks water and displaces oxygen of water

Option B (Fluorine being very reactive attacks water and displaces oxygen of water) is correct because fluorine is a very strong oxidizing agent and reacts violently with water, displacing oxygen.

75 Hard

75 of 184

Understanding +4 | -1

Oxidation states of the metal in the minerals haematite and magnetite, respectively, are

View answer and explanation

Correct option: D

III in haematite and II, III in magnetite

Option D (III in haematite and II, III in magnetite) is correct because in haematite (Fe2O3), iron has an oxidation state of +3, and in magnetite (Fe3O4), iron has oxidation states of +2 and +3.

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76 Medium

76 of 184

Understanding +4 | -1

In the reaction,

\mathrm{S}{\mathrm{O}_2} + 2{\mathrm{H}_2}\mathrm{S} \to 3\mathrm{S} + 2{\mathrm{H}_2}\mathrm{O}

the substance that oxidizes is,

View answer and explanation

Correct option: A

{\mathrm{H}_2}\mathrm{S}

Option A (

\mathrm{H}_2\mathrm{S}

) is correct because H2S is oxidized in the reaction, losing electrons and causing the reduction of SO2.

77 Medium

77 of 184

Remembering +4 | -1

For monoatomic ions, the oxidation number is equal to

View answer and explanation

Correct option: A

charge on the ion

Option A (charge on the ion) is correct because the oxidation number of a monoatomic ion is defined as its charge.

78 Easy

78 of 184

Remembering +4 | -1

Which of the following is the most powerful oxidizing agent?

View answer and explanation

Correct option: A

\mathrm{F}_2

Option A (

\mathrm{F}_2

) is correct because fluorine is the strongest oxidizing agent due to its high electronegativity and tendency to gain electrons.

79 Easy

79 of 184

Remembering +4 | -1

The burning of hydrogen is called :

View answer and explanation

Correct option: C

Oxidation

Option C (Oxidation) is correct because burning involves rapid reaction with oxygen, which is the definition of oxidation.

80 Easy

80 of 184

Analyzing +4 | -1

Which of the following has been arranged in order of increasing oxidation number of Nitrogen

View answer and explanation

Correct option: C

NH_4^ + < {N_2}{H_4} < N{H_2}OH < {N_2}O

Option C (NH4+ < N2H4 < NH2OH < N2O) is correct because it correctly orders the compounds based on increasing oxidation numbers of nitrogen: -3 < -2 < -1 < +1.

81 Easy

81 of 184

Application +4 | -1

Oxidation numbers of two cl atoms in bleaching powder

\left( {CaOC{l_2}} \right)

are,

View answer and explanation

Correct option: B

+ 1,\mathrm{ } - 1

Option B (+1, -1) is correct because bleaching powder is a mixed salt containing both hypochlorite (OCl-) and chloride (Cl-) ions, resulting in +1 and -1 oxidation states for the two chlorine atoms.

82 Easy

82 of 184

Remembering +4 | -1

The oxidation number of

\mathrm{H}

in sodium hydride is

View answer and explanation

Correct option: C

-1

Option C (-1) is correct because hydrogen has an oxidation number of -1 when bonded to a more electropositive element like sodium.

83 Hard

83 of 184

Understanding +4 | -1

C{u^{2 + }}

salt reacts with potassium iodide to give

View answer and explanation

Correct option: A

C{u_2}{l_2}

Option A (

C{u_2}{l_2}

) is correct because Cu2+ oxidizes I- to I2 and is itself reduced to Cu+, which then forms Cu2I2 (cuprous iodide).

84 Medium

84 of 184

Application +4 | -1

\mathrm{MnO}_4^ -

is a good oxidising agent in different medium changing to

\mathrm{MnO}_4^ - \to \mathrm{M}{\mathrm{n}^{2 + }}

\to \mathrm{MnO}_4^{2 - }, \to \mathrm{Mn}{\mathrm{O}_2}, \to \mathrm{M}{\mathrm{n}_2}{\mathrm{O}_3}

Changes in oxidation number respectively are

View answer and explanation

Correct option: C

5,1,3,4

Option C (5,1,3,4) is correct because the changes in oxidation number of Mn are calculated as 5, 1, 3, and 4 respectively for the given transformations.

85 Hard

85 of 184

Remembering +4 | -1

Titrations in which

{\mathrm{I}_2}

solution is used as intermediate are known as titrations.

View answer and explanation

Correct option: B

Iodimetric

Option B (Iodimetric) is correct because iodimetric titrations use a standard solution of I2 as the titrant.

86 Easy

86 of 184

Remembering +4 | -1

The correct name for

{NO}_2

using stock notation is

View answer and explanation

Correct option: B

Nitrogen (iv) oxide

Option B (Nitrogen (iv) oxide) is correct because stock notation indicates the oxidation state of the element using Roman numerals.

87 Hard

87 of 184

Application +4 | -1

Oxidation state of '

\mathrm{V}^{\prime}

\mathrm{Rb}_4 \mathrm{Na}\left[\mathrm{HV}_{10} \mathrm{O}_{28}\right]

View answer and explanation

Correct option: A

+5

Option A (+5) is correct because Rb has +1, Na has +1, H has +1, and O has -2, balancing the charge of the complex ion.

88 Easy

88 of 184

Application +4 | -1

The oxidation state of oxygen atom in potassium superoxide is

View answer and explanation

Correct option: B

- \frac{1}{2}

Option B (-1/2) is correct because in potassium superoxide (

KO_2

), potassium has a +1 oxidation state, and the two oxygen atoms share a -1 charge, resulting in each oxygen having an oxidation state of -1/2.

89 Easy

89 of 184

Analyzing +4 | -1

The most powerful oxidizing agent from the following is

View answer and explanation

Correct option: D

\mathrm{H}_2 \mathrm{SO}_4

Option D (H2SO4) is correct because sulfuric acid is a strong oxidizing agent due to sulfur's ability to be reduced from +6 to lower oxidation states.

90 Easy

90 of 184

Understanding +4 | -1

The violent reaction between sodium and water is an example of :

View answer and explanation

Correct option: C

Redox reaction

Option C (Redox reaction) is correct because the reaction involves both oxidation (loss of electrons) and reduction (gain of electrons).

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