Redox Reactions

The term oxidation was coined for the class of chemical reactions where in one of the following options take place.
1. Addition of oxygen to a substance
2. Addition of electropositive element to a substance
3. Removal of electronegative element from a substance
4. Addition of hydrogen to a substance
The term reduction has one of the following options taking place.
1. Removal of oxygen from a substance
2. Addition of electronegative element to a substance
3. Removal of hydrogen to a substance
4. Removal of electropositive element from a substance
Copper nitrate is a blue coloured solution. Place a strip of metallic zinc in an aqueous solution of copper nitrate for about one hour. What happens?
1. Zinc strip becomes coated with blue colour
2. The blue colour of the solution turns to red
3. The aqueous solution of copper nitrate turns green in colour and mettallic zinc strip turns darker in colour.
4. The blue colour of the solution becomes more intense blue.
Redox reaction between copper and aqueous solution of silver nitrate happens when copper rod is dipped in silver nitrate solution. What happens in the final stage?
1. Silver deposits on the rod; Ag⁺(aq) is oxidised to Ag(s)
2. The solution turns intense blue; and silver is deposited on copper rod
3. Silver deposits in the solution; Ag⁺(aq) is reduced to Ag(s).
4. Copper deposits in the solution; Cu(aq) is reduced to Cu₂ ⁺(s)
The electron releasing tendency of the metals, zinc, copper and silver is in the order:
1. Cu>Ag>Zn
2. Zn>Cu>Ag
3. Ag>Cu>Zn
4. Zn>Ag>Cu
In the reaction of metallic cobalt placed in nickel sulphate solution, there is a competition for release of electrons At equilibrium, chemical tests reveal that both Ni₂⁺ (aq) and Co₂⁺ (aq) are present at moderate concentrations. The result is that:
1. Only [Co(s) and Ni₂⁺ (aq)] are favoured
2. Only one reactant and one product is greatly favoured.
3. Only Co₂⁺ (aq) and Ni (s)] are favoured
4. Neither the reactants nor the products are greatly favoured.
Oxidation number denotes the oxidation state of an element in a compound ascertained on the basis that electron in a covalent bond belongs:
1. Entirely to more electronegative element
2. Entirely to transition elements if present
3. Entirely to halogens in a compound
4. Entirely to more electronegative element
The highest value of oxidation number changes from 1 to 7:
1. The first three groups
2. In alkaline earth metals
3. In the atoms of transition elements
4. Across the third period in the periodic table
The oxidation number of oxygen in most compounds is:
1. 4
2. -2
3. -3
4. 1
Aurous chloride and auric chloride are written as Au(l)Cl and Au(lll)Cl₃.The roman numeral in parenthesis after the symbol of the metal in the molecular formula represents the:
1. Basic character
2. Electronegativity
3. Ionic state
4. Oxidation number
Formation of coloured solution is possible when metal ion in the compound contains,
1. lone pair of electrons
2. Unpaired electrons
3. Paired electrons
4. Negative ionic state
All combustion reactions, which make use of elemental dioxygen, as well as other reactions involving elements other than dioxygen are:
1. Decomposition reactions
2. Disproportionation reactions
3. Combination reaction
4. Displacement reactions
Standard electrode potential of three metals X, Y and Z are –1.2 V, +0.5 V and –3.0 V respectively. The reducing power of these metals will be:
1. Y > Z > X
2. Y > X > Z
3. Z > X > Y
4. X > Y > Z
A metal in a compound can be displaced by another metal in the uncombined state. Which metal is a better reducing agent in such a case?
1. Better reducing agent is the one that loses less electrons
2. Both are same in reducing capacity
3. The reduced metal is a better reducing agent than the reducing metal
4. Better reducing agent is the one that loses more electrons
Displacement of hydrogen from cold water is done by,
1. Superoxides
2. All transition elements
3. All alkali metals
4. All alkaline earth metals
Fractional Oxidation Number exists because,
1. The average oxidation state of the element is divided by two
2. Middle carbon in such elements has always zero oxidation state
3. Electrons are never shared/transferred in that element
4. The element is present in different oxidation states
The strength of a reductant/oxidant in redox systems can be determined,
1. By taking into consideration only half reactions involving oxidation
2. By taking into consideration the different oxidation states of the atom in the element
3. By the titration method using a redox sensitive indicator
4. By taking into consideration only half reactions involving reduction
One of the following has application in electrode processes and cells,
1. The concept of redox reactions
2. Half reactions involving oxidation
3. Half reactions involving reduction
4. The different oxidation states of the atom in the element
Zn²⁺/Zn represents:
1. Oxidation number of +2 of Zinc
2. Oxidised form of Zinc
3. Half reactions involving reduction
4. The different oxidation states of the atom in the element
In Daniell cell, direction of current is:
1. Opposite to the direction of electron flow
2. Towards centre
3. In the same direction of electron flow
4. Towards anode
The flow of current is possible in Daniel cell only,
1. If there is a potential difference between the copper and zinc electrodes
2. If the transfer of electrons does take place directly from Zn to Cu²⁺
3. If the zinc and copper rods are connected by a salt bridge only
4. If the zinc and copper rods are connected by the platinum wire only
In oxygen difluoride (OF₂) and dioxygen difluoride(O₂F₂), the oxygen is assigned an oxidation number of:
1. +2 and +4
2. +2
3. +4 and +3
4. +2 and +1
Oxidation number of (1/2) is assigned to oxygen atom in:
1. Superoxides
2. When oxygen is bonded to fluorine
3. When oxygen is bonded to metals
4. Peroxides
Assign oxidation number to S in KAl (SO₄)₂.12 H₂O
1. +5
2. +12
3. +4
4. 6.0
If an excess of P₄ is treated with F₂, then_____will be produced wherein the oxidation number of P is +3. The compound is
1. PF₆
2. PF
3. PF₅
4. PF₃
Which of the following is not an example of redox reaction?
1. 2K + F₂ → 2KF
2. BaCl₂ + H₂SO₄ → BaSO₄ + 2HCl
3. Fe₂O₃ + 3CO → 2Fe + 3CO₂
4. CuO + H₂ → Cu + H₂O
Electrochemical processes for extraction of highly reactive metals and non-metals involves one of the following. Choose the most appropriate option.
1. Reaction with inert gases
2. Oxidation processes
3. Redox processes
4. Reduction processes
Assign oxidation number to P in NaH₂PO₄
1. +4
2. +1
3. +6
4. 5.0
2 Na⁺ (s) → 2 Na⁺ (g) + 2e^- H₂ (g) + 2e^- n2H⁺ (g):
1. Electronegativity of sodium determines the direction of the reaction
2. Hydrogen is oxidised
3. Sodium is reduced
4. Sodium is oxidised and hydrogen is reduced
In the free or the uncombined state, each atom in O₂O₃, P₄, S₈ and Mg has the oxidation number:
1. Seven
2. Two
3. Three
4. Zero
For ions composed of only one atom, the oxidation number is equal to the:
1. Always +1
2. Charge on the ion
3. Always -1
4. Sum of different oxidation states
Hydrogen is prepared from H₂O by adding:
1. Ag, which acts as reducing agent
2. Au, which acts as oxidising agent
3. Ca, which acts as reducing agent
4. AI, which acts as oxidising agent
An oxidation number of +1 is found in all their compounds of one of the below given options:
1. Superoxides
2. All alkaline earth metals
3. All transition elements
4. All alkali metals
An oxidation number of +1 is found in all their compounds of one of the below given options:
1. All alkaline earth metals
2. Superoxides
3. All alkali metals
4. All transition elements
The oxidation number of hydrogen in LiH, NaH and CaH₂ is:
1. 1 and 2
2. -2
3. -1 and -2
4. -1.0
Chlorine, bromine and iodine when combined with oxygen, have oxidation numbers:
1. -2
2. -1 or any negative number
3. -1
4. +1 or any positive number
The oxidation number of an element in a compound is evaluated on the basis of certain rules. Which of the following rules is not correct in this respect?
1. The oxidation number of hydrogen is always +1.
2. An element in the free or the uncombined state bears oxidation number zero.
3. In all its compounds, the oxidation number of fluorine is –1.
4. The algebraic sum of all the oxidation numbers in a compound is zero.
The more positive the value of E0, the greater is the tendency of the species to get reduced. Using the standard electrode potential of redox couples given below find out which of the following is the strongest oxidising agent.

E0values: Fe³⁺/Fe²⁺ = +0.77; I₂ (s)/l⁻ = +0.54; Cu²⁺/Cu = + 0.34; Ag⁺/Ag = + 0.80V
1. I₂(s)
2. Fe³⁺
3. Zn
4. None of these
Using the standard electrode potential, find out the pair between which redox reactions is not feasible.

E0values: Fe³⁺/Fe²⁺ = +0.77; I²/l− = +0.54; Cu²⁺/Cu = + 0.34; Ag⁺/Ag = + 0.80 V
1. Fe³⁺ and Cu
2. Ag⁺ and Cu
3. Fe³⁺ and l^-
4. Ag and Fe³⁺
An oxidation number of +2 is found in all their compounds of one of the below given options.
1. Superoxides
2. All alkaline earth metals
3. All transition elements
4. All alkali metals
The oxidizing power of halogens increase in the order of:
1. Cl₂ < F₂ < I₂ < Br₂
2. F₂ < I₂ < Br₂ < Cl₂
3. I₂ < Br₂ < Cl₂ < F₂
4. Br₂ < Cl₂ < F₂ < I₂
In which of the following compounds, an element exhibits two different oxidation states.
1. N₂H₄
2. NH₂OH
3. NH₄NO₃
4. N₃H
Which of the following arrangements represent increasing oxidation number of the central atom?
1. Cro⁻₂, Clo⁻₃, Cro^2-₄, Mno⁻₄
2. Cro<sup−₂, Cro²⁻₄, Mno⁻₄, Clo⁻₃
3. Cro²⁻₄, Mno⁻₄, Cro⁻₂, Clo⁻₃
4. Clo⁻₃, Cro⁽²⁻⁾₄, Mno⁻₄, Cro⁻₂
The largest oxidation number exhibited by an element depends on its outer electronic configuration. With which of the following outer electronic configurations the element will exhibit largest oxidation number?
1. 3d¹s²
2. 3d³4s²
3. 3d⁵4s²
4. 3d⁵4s¹
Consider the elements: Cs, Ne, I and F. Identify the element which exhibits neither the negative nor does the positive oxidation state.
1. Cs
2. Ne and F
3. Ne
4. F
Which of the following elements does not show disproportionation tendency?
1. F
2. Br
3. Cl
4. I
Consider the elements: Cs, Ne, I and F. Identify the element(s) that have disproportionation tendency.
1. Cs and I
2. Ne
3. Cs
4. I
The exhibition of various oxidation states by an element is also related to the outer orbital electronic configuration of its atom. Atom(s) having which of the following outermost electronic configurations will exhibit more than one oxidation state in its compounds.
1. 3s²3p³
2. 3d¹4s²
3. 3s¹
4. 3d²4s²
Which of the following electrodes will act as anodes, when connected to Standard Hydrogen Electrode?
1. Fe/Fe³⁺ E⁰ = − 0.44
2. Cu/Cu²⁺ E⁰ = + 0.34
3. Al/Al³⁺ E⁰ = - 1.66
4. F₂(g)/2F⁻(aq) E⁰ = + 2.87
The decomposition of hydrogen peroxide to form water and oxygen is an example of:
1. Displacement reactions
2. Combination reactions
3. Decomposition reactions
4. Disproportionation reaction
Identify the correct statements with reference to the given reaction P₄ + 3OH^- + 3 H₂O → PH₃ + 3H₂PO^-₂
1. Phosphorus is undergoing oxidation as well as reduction.
2. Hydrogen is undergoing oxidation as well as reduction
3. Phosphorus is undergoing reduction only.
4. Phosphorus is undergoing oxidation only.
The electron releasing tendency of the metals, zinc, copper and silver is in the order:
1. Ag > Cu > Zn
2. Cu > Ag > Zn
3. Zn > Cu > Ag
4. Zn > Ag > Cu
A complex compound in which the oxidation number of a metal is zero is:
1. K₃[Fe (CN)₆]
2. [Ni (CO)₄]
3. [Pl(NH₃)₄]Cl₂
4. K₄[Fe (CN)₆]
Identify the correct statement (s) in relation to the following reaction: Zn + 2HCl → ZnCl₂ + H₂
1. Hydrogen ion is acting as a reductant
2. Hydrogen ion is acting as an oxidant
3. Zinc is acting as an oxidant
4. Chlorine is acting as a reductant
The standard emf of a galvanic cell involving 2 moles of electrons in its redox reaction is 0.59 V. The equilibrium constant for the redox reaction of the cell is:
1. 10⁵
2. 10¹⁰
3. 10²⁰
4. 10
Dalda is prepared from oils by:
1. Distillation
2. Oxidation
3. Hydrolysis
4. Reduction
Formation of coloured solution is possible when metal ion in the compound contains:
1. Lone pair of electrons
2. Unpaired electrons
3. Paired electrons
4. Negative ionic state
Standard electrode potential of three metals X, Y and Z are –1.2 V, +0.5 V and –3.0 V respectively. The reducing power of these metals will be:
1. Y > X > Z
2. Y > Z > X
3. Z > X > Y
4. X > Y > Z
The oxidation state of iron in K₄[Fe(CN )₆] is:
1. 4
2. 2.0
3. 1
4. 3
The standard emf of a galvanic cell involving 3 moles of electrons in its redox reaction is 0.59 V. The equilibrium constant for the reaction of the cell is ______.
1. 10²⁰
2. 10²⁵
3. l0³⁰
4. 10¹⁵
A metal in a compound can be displaced by another metal in the uncombined state. Which metal is a better reducing agent in such a case?
1. The reduced metal is a better reducing agent than the reducing metal
2. Better reducing agent is the one that loses less electrons
3. Both are same in reducing capacity
4. Better reducing agent is the one that loses more electrons
Hydrogen is prepared from H₂O by adding:
1. Au, which acts as oxidising agent
2. Ca, which acts as reducing agent
3. AI, which acts as oxidising agent
4. Ag, which acts as reducing agent
In the reaction 2H₂O₂ → 2H₂O + O₂
1. Oxygen is reduced only
2. Oxygen is both oxidised and reduced
3. Oxygen is oxidised only
4. Oxygen is neither oxidised nor reduced
Consider the elements: Cs, Ne, I and F. Identify the element(s) that exhibits only negative oxidation state.
1. F
2. I
3. Cs and F
4. s
Consider the elements :Cs, Ne, I and F. Identify the element(s) that exhibits only negative oxidation state.
1. Cs
2. I
3. Cs and I
4. Ne
Consider the elements :Cs, Ne, I and F. Identify the element that exhibits both positive and negative oxidation states.
1. I
2. Ne and F
3. Ne
4. Cs
Consider the elements: Cs, Ne, I and F. Identify the element which exhibits neither the negative nor does the positive oxidation state.
1. Ne and F
2. Cs
3. Ne
4. s
In Ostwald’s process for the manufacture of nitric acid, the first step involves the oxidation of ammonia gas by oxygen gas to give nitric oxide gas and steam. What is the maximum weight of nitric oxide that can be obtained starting only with 10.00 g. of ammonia and 20.00 g of oxygen ?
1. 25g of NO
2. 15g of NO
3. 20g of NO
4. 16g of NO
Which one of the following oxidation state is the most common among the lanthanoids?
1. 4
2. 2
3. 5
4. 6
A mixture of potassium chlorate, oxalic acid and sulphuric acid is heated. During thr reaction which element undergoes maximum change in the oxidation number?
1. Cl
2. C
3. S
4. H
Oxidation numbers of P in PO₄³⁻ of S in SO₄²⁻ and that of Cr in Cr²O₇²⁻ are respectively:
1. -3,+6 and +6
2. +5, +3 and +6
3. +3, +6 and +5
4. +5, +3 and +4
In which of the following compounds, nitrogen exhibits the highest oxidation state?
1. N₃H
2. NH₂OH
3. N₂H₄
4. None of these
When Cl₂ gas reacts with hot and concentrated sodium hydroxide solution, the oxidation number of chlorine changes from,
1. Zero to -1 and zero to +3
2. Zero to +1 and zero to -3
3. Zero to +1 and zero to -5
4. Zero to -1 and zero to +5
The pair of compounds that can exist together is,
1. FeCl₃,SnCl₂
2. HgCl₂, SnCl₂
3. FeCl₂, SnCl₂
4. FeCl₃, KI
(I) H₂O + O₃ → H₂O + 2O₂
(II) H₂O₂ + Ag₂O → 2Ag + H₂O + O₂
Role of hydrogen peroxide in the above reactions is respectively,
1. Oxidizing in (I) and Reducing in (II)
2. Reducing in (I) and Oxidizing in (II)
3. Reducing in (I) and (II)
4. None of these
In acidic medium, H₂O₂ changes Cr₂O₇²⁻ to CrO₅ which has two (-O-O-) bonds. Oxidation state of Cr in CrO₅ is
1. +5
2. +3
3. +6
4. None of these
Following raection describes the rusting of iron
4Fe + 3O₂ → 4Fe³⁺ + 6O²⁻
Which one of the following statement is incorrect?
1. This is an example of a redox reaction
2. Metallic iron is reduced to Fe³⁺
3. Fe³⁺ is an oxidizing agent
4. None of these
Identify the correct statement about H₂O₂
1. It acts as reducing agent only
2. It acts as both oxidizing and reducing agent
3. It is neither an oxidising and reducing agent
4. It acts as oxidizing agent only
In C+H₂O → CO + H₂, H₂O acts as,
1. Oxidizing agent
2. Reducing agent
3. Both Oxidizing agent and Reducing agent
4. None of these
Which substance is serving as a reducing agent in the following reaction:
14H⁺ + Cr₂O₇²⁻ + 3Ni → 2Cr³⁺ + 7H₂O + 3Hi²⁺
1. H₂O
2. Ni
3. H⁺
4. None of these
HNO² acts both as reductant and oxidant, while HNO₃ acts only as oxidant. it is due to their,
1. Solubility Ability
2. Maximum Oxidation Number
3. Minimum Oxidation Number
4. Minimum Number of Valence Electrons
Oxidation number of nickel in Ni(CO)₄ is,
1. 0
2. +4
3. -4
4. +2
The oxidation nember of carbon in CH₂Cl₂ is
1. 0
2. +2
3. -2
4. +4
Which of the following statement is correct?
1. Hydrogen has oxidation number -1 and +1
2. Hydrogen has same electronegativity as halogen
3. Hydrogen will not be liberated at anode
4. Hydrogen has same ionization potential as alkali metals
An element which never has a positive oxidation nember in any of its compounds,
1. Boron
2. Oxygen
3. Chlorine
4. Fluorine
If HNO₃ changes into N₂O, the oxidation nember is changed by,
1. +2
2. -1
3. 0
4. +4
The Oxidation number of iron in the compound K₄[Fe(CN)₆] is
1. +6
2. +4
3. +3
4. +2
The brown ring complex compound is formulated as [Fe(H₂O)₅NO]SO₄. The oxidation state of iron is,
1. 1
2. 2
3. 3
4. 0
Which is the oxidation number of sulphur in Na₂S₄O₆?
1. 2/3
2. 3/2
3. 3/5
4. 5/2
Identify the element which can have highest oxidation numbers,
1. N
2. O
3. Cl
4. C
Which is the net charge on ferrous ion?
1. +2
2. +3
3. +4
4. +5
Which of the following reactions involves oxidation-reduction?
1. NaBr + HCl → NaCl + HBr
2. HBr + AgNO₃ → AgBr + HNO₃
3. H₂ + Br₂ → 2HBr
4. 2NaOH + H₂SO₄ → Na₂SO₄ + 2H₂O
The equivalent weight of phosphoric acid (H₃PO₄) in the reaction NaOH + H₃PO₄ → NaH₂PO₄ +H₂O is,
1. 25
2. 49
3. 59
4. 98
For decolourization of 1 mole of KMnO₄, the moles of H₂O₂ required is,
1. 1/2
2. 3/2
3. 5/2
4. 7/2
The oxidation number of sulphur in H₂S₂O₇ and iron in K₄Fe(CN)₆ is respectively,
1. +6 and +2
2. +2 and +2
3. +8 and +2
4. +6 and +4
MnO₄²⁻ in neutral aqueous medium is disproportionate to
1. 2/3 mole of MnO₄⁻ and 1/3 mole of MnO₂
2. 1/3 mole of MnO₄⁻ and 2/3 mole of MnO₂
3. None of these
4. both 1/3 mole of MnO₄⁻ and 2/3 mole of MnO₂ and 2/3 mole of MnO₄⁻ and 1/3 mole of MnO₂
Oxidation can be defiened as the terms
(I) gain of electron and hydrogen
(II) gain of oxygen and loss of electron
(III) increase on oxidation number
(IV) decrease in oxidation number
1. (I) and (II)
2. (I) and (IV)
3. (I) and (III)
4. (II) and (III)
The oxidation number of S in H₂S₂O₈ is
1. +2
2. +4
3. +6
4. +7
In the reaction H₂S + NO₂ → H₂O + NO + S
H₂S is,
1. Oxidised
2. Reduced
3. Both Oxidised and Reduced
4. None of these
In which of the following processes nitrogen is oxidised?
1. NH₄⁺ → N₂
2. NO₃⁻ → NO
3. NO₂ → NO₂⁻
4. None of these
Reduction is defined in terms of,
(I) electronation and hydrogenation
(II) deelectronation and gain of electron
(III) increase in oxidation number
(IV) decrease in oxidation number
1. (II) and (III)
2. (I) and (III)
3. (I) and (IV)
4. (I) and (II)
Which one of the following has the highest oxidation number of iodine?
1. K₃
2. KI
3. IF₅
4. KIO₄
Which one of the following reactions does not involve either oxidation or reduction?
1. VO₂⁺ → V₂O₃
2. Na → Na⁺
3. CrO₄²⁻→ Cr₂O₇²⁻
4. Zn²⁺ → Zn
In the following reaction,
2Br₂ → 6CO₃²⁻ + 2H₂O = 5Br⁻ + BrO₃⁻ + 6HCO₃
1. Bromine is oxidised and carbonate is reduced
2. Bromine is reduced and water is oxidised
3. Bromine is neither reduced nor oxidised
4. Bromine is both reduced and oxidised
In the following reaction,
4P + 3KOH + 3H₂O → 3KH₂PO₂ + PH₃
1. P is oxidised as well as reduced
2. P is reduced only
3. P is oxidised only
4. None of these
In the following reaction,
Cr₂O₇⁻ + 14H⁺ + 6I⁻ → 2Cr³⁺ + 3H²O + 3I₂
Which element is reduced
1. Cr
2. H
3. O
4. I
If HNO₃ changes into N₂O, the oxidation number is changed by,
1. +2
2. -1
3. 0
4. +4
Oxidation number of sulphur in H₂SO₅ is,
1. +2
2. +4
3. +8
4. +6
In which of the following compounds transition metal is in oxidation state zero
1. [Co(NH₃)₆]Cl₂
2. [Fe(H₂O)₆SO₄]
3. [Ni(CO)₄]
4. [Fe(H₂O)₃](OH)₂
Oxidation number of nickle in Ni(Cl)₄ is
1. +2
2. +4
3. -4
4. 0
Which of the following is not a reducing agent?
1. NaNO₂
2. NaNO₃
3. HI
4. SnCl₂
The brown ring complex compound is formulated as [Fe(H₂O)₅NO]SO₄. The Oxidation state of iron is,
1. 1
2. 2
3. 3
4. 0
The oxidation number of Mn in MnO₄⁻ is
1. +6
2. -5
3. +7
4. +5
In C + H₂O → CO + H₂, H₂O acts as
1. Oxidising agent
2. Reducing agent
3. Oxidising agent and Reducing agent
4. None of these
The oxidation numbers of Fe and S in iron pyrites are
1. 3, -1
2. 2, -1
3. 3, -1.5
4. 4, -2
In which of the following compounds the oxidation number of carbon in maximum
1. HCHO
2. CH₃OH
3. CHCl₃
4. C₁₂H₂₂O₁₁
Sulphur has lowest oxidation number in
1. H₂SO₃
2. SO₂
3. H₂SO₄
4. H₂S
A solution of sulphur dioxide in water reacts with H₂S precipitating sulphur. Here sulphur dioxide acts as,
1. As oxidising agent
2. A reducing agent
3. An acid
4. A catalyst
In ferrous ammonium sulphate oxidation number of Fe is
1. +3
2. +2
3. +1
4. -2
The oxidation number of Cr in K₂Cr₂O₇ is
1. -2
2. -7
3. +2
4. +6
Oxidation number of carbon in CH₃-Cl is
1. -3
2. -2
3. -1
4. 0
In which of the following reactions H₂O₂ ia s reducing agent?
1. 2FeCl₂ + 2HCl + H₂O₂ → 2FeCl₃ + 2H₂O
2. Cl₂ +H₂O₂ → 2HCl + O₂
3. 2HI + H₂O₂ → 2H₂O + I₂
4. 0, -1
Oxidation numbers of two Cl atoms in bleaching powder, CaOCl₂ are
1. -1, -1
2. +1, -1
3. +1, +1
4. 0, -1
Select the compound in which chlorine is assigned the oxidation number of +5
1. HClO₄
2. HClO₂
3. HClO₃
4. HCl
When NaCl is dissolved in water the sodium ion becomes
1. Oxidised
2. Reduced
3. Hydrolysed
4. Hydrated
Oxidation number of osmium (Os) in OsO₄ is
1. +8
2. +6
3. +7
4. +4
Whcih substance is serving as a reducing agent in the following reaction?
14H⁺ + Cr₂O₇²⁻ + 3Ni → 2Cr₃⁺ + 7H₂O + 3Ni²⁺
1. H₂O
2. Ni
3. H⁺
4. Cr₂O₇²⁻
The oxidation number of iron in the compound K₄[Fe(CN)₆] is
1. +2
2. +4
3. +3
4. +6
The compound that can work both as oxidising and reducing is,
1. KMnO₄
2. H₂O₂
3. BaO₂
4. K₂Cr₂O₇
When KMnO₄ acts as an oxidising agent and ultimately forms [MnO₄]⁻², MnO₂, Mn₂O₃, Mn⁺², then the number of electrons transferred in each case respectively is,
1. 4,3,1,5
2. 1,5,3,7
3. 1,3,4,5
4. 1,5,4,3
Which of the following acid possesses oxidising, reducing and complex forming properties?
1. HNO₃
2. H₂SO₄
3. HCL
4. HNO₂
Oxidation number of P in KH₂PO₂ is
1. -4
2. +3
3. +5
4. +1
Which one is oxidising substance?
1. C₂H₂O₂
2. CO
3. H₂S
4. CO₂
The oxidation number of phosphorus in Ba(H₂PO₂)₂ is
1. +1
2. -1
3. +2
4. +3
The oxidation number and the electronic configuration of sulphur in H₂SO₄
1. +6; 1s²2s²2p⁶
2. +2; 1s²2s²2p⁶3s²3p²
3. +3; 1s²2s²2p⁶3s²3p¹
4. +4; 1s²2s²2p⁶3s²
The compound which could not act both as oxidising and reducing agent is
1. SO₂
2. MnO₂
3. Al₂O₃
4. CrO
In XeO₃ and XeF₆ the oxidation state of Xe is,
1. +4
2. +1
3. +6
4. +3
In the reaction,
Ag₂O + H₂O₂ → 2Ag + H₂O + O₂, H₂O₂ acts as
1. Reducing agent
2. Oxidising agent
3. Bleaching agent
4. None of these
The oxidation state of Cr in Cr₂O₇²⁻ is
1. 4
2. 6
3. -6
4. -2
Oxidation number of sulphur in S₂O₃²⁻ is
1. -2
2. +6
3. +2
4. 0
M⁺³ ion loses 3e⁻. Its oxidation number will be,
1. 0
2. +3
3. +6
4. -3
Which of the following substances acts as an oxidising as well as reducing agent?
1. Na₂O
2. SnCl₂
3. Na₂O₂
4. NaNO₂
Oxidation state of oxygen atom in potassium superoxide is
1. 0
2. -1/2
3. -1
4. -2
Amongst the following identify the species with an atom in +6 oxidation state.
1. MnO₄⁻
2. Cr(CN)₆³⁻
3. NiF₆²⁻
4. 2/3
What is the oxidation number of sulphur in Na₂S₄O₆?
1. 5/2
2. 3/2
3. 3/5
4. 2/3
HNO₂ acts both as reductant and as oxidant, while HNO₃ acts only as oxidant. It is due to their,
1. Solubility ability
2. Maximum oxidation number
3. Minimum oxidation number
4. Minimum number of valence electrons
Oxidation state of chlorine in perchloric acid is,
1. -1
2. 0
3. -7
4. +7
Carbon is in the lowest oxidation state in
1. CH₄
2. CCl₄
3. CF₄
4. CO₂
Oxidation number of carbon in H₂C₂O₄ is
1. +4
2. +3
3. +2
4. +1
Which of the following can act as an acid and a base?
1. HCIO₃⁻
2. H₂PO₄⁻
3. HS⁻
4. CO₂
H₂O₂ reduces MnO₄⁻ ion to,
1. Mn⁺
2. Mn²⁺
3. Mn²⁻
4. None of these
The value of x in the partial redox equation,
MnO₄⁻ + 8H⁺ + xe ↔ Mn²⁺ + 4H₂O is
1. 5
2. 3
3. 1
4. 0
During the disproportionational of I₂ to iodide and iodate ions, the ratio of iodate and iodide ions formed in alkaline medium is,
1. 1:5
2. 5:1
3. x=2, y=5, z=8
4. x=2, y=5, z=5
In the redox reaction,
xMnO + yPbO₂ + zHNO₃ → HMnO₄ + Pb(NO₃)₂ + H₂O
1. x=2, y=5, z=10
2. x=2, y=7, z=8
3. x=2, y=5, z=8
4. x=2, y=5, z=5
In the balanced chemical reaction,
IO₃⁻ + aI⁻ + bH⁺ → cH₂O + dI₂
a, b, c, d respectively correspond to,
1. 5,6,5,5
2. 5,3,6,3
3. 3,5,3,6
4. 5,6,3,3
C₂H₆(g) + nO₂ → CO₂(g) + H₂O(I)
In this equation, the ratio of the coefficients of CO₂ and H₂O is
1. 1:1
2. 2:3
3. 3:2
4. 1:3
The number of electrons involved in the reduction of Cr₂O₇²⁻ in acidic solution to Cr³⁺ is
1. 0
2. 2
3. 3
4. 5
2MnO₄⁻ + 5H₂O₂ + 6H⁺ → 2Z + 5O₂ + 8H₂O, in this reaction Z is,
1. Mn⁺²
2. Mn⁺⁴
3. MnO₂
4. Mn
H₂O can be oxidised to
1. H₂ and O₂
2. O₂
3. OH⁻
4. O₂⁻
When ZnS is boiled with strong nitrc acid, the products are zinc nitrates, sulphuric acis and nitrogen dioxide. What are the changes in the oxidation numbers of Zn, S and N?
1. +2,+4,-1
2. +2,+6,-2
3. 0,+4,-2
4. 0,+8,-1
In the following reaction,
2I⁻ + Cr₂O₇²⁻ + 14H⁺ → I₂ + 2Cr³⁺ + 7H₂O
Unbalanced parts are,
1. H⁺, H₂O
2. Cr₂O₇²⁻, Cr³⁺
3. I⁻, I₂
4. None of them are balanced
4.9 of K₂Cr₂O₇ is taken to prepare 0.1 L of the solution. 10mL of this solution is further taken to oxidise Sn⁴⁺ ion Sn⁴⁺ so produced is used in second reaction to prepare Fe³⁺ ion formed will be (assume all other components are in sufficient amount) [Molar mass of K₂Cr₂O₇ = 294g].
1. 5
2. 20
3. 10
4. None of these
One gram of Na₃AsO₄ is boiled with excess of solid KI in presence of strong HCl. The iodine evolved is absorbed in KI solution and titrated against 0.2 N hyposolution. Assuming the reaction to be
AsO₄³⁻ + 2H⁺ + 2I⁻ → AsO₃³⁻ + H₂O + I₂,
calculate the volume of thiosulphate hypo consumed.
[Atomic weight of As = 75]
1. 48.1mL
2. 38.4mL
3. 24.7mL
4. 30.3mL
25mL of 0.50M H₂O₂ solution is added to 50mL of 0.20M KMnO₄ in acid solution. Which of the following statements is true?
1. 0.010 mole of oxygen is liberated
2. 0.005 mole of KMnO₄ are left
3. 0.030 g atom of oxygen gas is evolved
4. 0.0025 mole of H₂O₂ does not react with KMnO₄
One mole of CaOCl₂ is dissolved in water and excess of KI addded. Hypo (Na₂S₂O₃) required to react with the oxidised part completely is
1. 1 mole
2. 2.0 moles
3. 1.5 moles
4. 2.5 moles
The number of moles of KMnO₄ reduced by one mole of KI in alkaline medium is:
1. One-fifth
2. Five
3. One
4. Two
0.3 g of an oxalate salt was dissolved in 100mL solution. The solution required 90mL of N/20 KMnO₄ for complete oxidation. The % of oxalate ion in salt is:
1. 33%
2. 66%
3. 70%
4. 40%
How many litres of a 0.5 N solution of an oxidising agent are reduced by 2 litres of a 2.0 N solution of a reducing agent?
1. 8
2. 4
3. 6
4. 7
During the disproportionation of iodine to iodide and iodate ions, the ratio of iodate and iodide ions formed in alkaline medium is:
1. 1:5
2. 5:1
3. 3:1
4. 1:3
If 25.8 ml of 0.101 M K₂Cr₂O₇ is required to titrate 10.0 ml of a liquid iron supplement, calculate the concentration of iron in vitamin solution
1. 0.780 M
2. 0.261 M
3. 4.35 x 10⁻⁴ M
4. 1.56 M
Mass of KHC₂O₄ (potassium acid oxalate) required to reduce 100ml of 0.02M KMnO₄ in acidic medium ( to Mn²⁺) is x g and to neutralise 100 ml of 0.05 M Ca(OH)₂ is y g, then
1. x=y
2. 2x=y
3. x=2y
4. None of these
The number of moles of K₂Cr₂O₇ that will be needed to react completely with one mole of ferric sulphite in acidic medium is
1. 0.4
2. 0.6
3. 1.0
4. 0.8
100 ml of a mixture of NaOH and Na₂SO₄ is neutralised by 10 ml of 0.5 M of H₂SO₄. Hence NaOH in 100 ml solution is,
1. 0.2 g
2. 0.4 g
3. 0.6 g
4. None of these
During the oxidation of arsenite to arsenate ion in alkaline medium, the number of moles of hydroxide ions involved per mole of arsenite ion are
1. 2
2. 3
3. 2/9
4. None of these
The number of moles of oxalate ions oxidised by one mole of MnO₄⁻ ion is
1. 1/5
2. 2/5
3. 5/2
4. 5
Starch paper is used to test for the presence of
1. Reducing agent
2. Oxidising agent
3. Iodide ion
4. Iodine
The molar ratio of Fe⁺⁺ to Fe⁺⁺⁺ in a mixture of FeSO₄ and Fe₂(SO₄)₃ having equal number of sulphate ions in both ferrous and ferric sulphate is:
1. 1:2
2. 3:2
3. 2:3
4. Cant be determined
Which is the best description of the behaviour of bromine in the reaction given below,
H₂O + Br₂ → HOBr + HBr
1. Oxidised only
2. Reduced only
3. Proton acceptor only
4. Both oxidised and reduced
Equivalent weight of NH₃ as a base is
1. 17
2. 17/3
3. 1.7
4. 17/2
In the reaction VO + Fe₂O₃ → FeO + V₂O₅, the eq. wt. of V₂O₅ is equal to its
1. Mol. Wt.
2. Mol. Wt./8
3. Mol. Wt./6
4. None of these
Equivalent mass of oxidising agent in the reaction, SO₂ + 2H₂S → 3S+ 2H₂O is
1. 32
2. 64
3. 16
4. 8
Equivalent weight of H₃PO₂ when it disproportionates into PH₃ and H₃PO₃ is (mol. wt. of H₃PO₂ = M)
1. M
2. (3M)/4
3. M/2
4. M/4
In the following unbalanced redox reaction,
Cu₃P + Cr₂O₇²⁻ → Cu²⁺ + H³PO₄ + Cr³⁺
Equivalent weight of H³PO₄ is
1. M/3
2. M/6
3. M/7
4. M/8
Equivalent weight of H₃PO₂ when it disproportionates into PH₃ and H₃PO₃ is ( mol. wt. of H₃PO₂ = M)
1. M
2. (3M)/4
3. M/2
4. M/4
Consider conversion of MnCl₂ into
(I) MnCl₃
(II) MnO₂
(IIi) MnO₄²⁻
(IV) MnO₄⁻
Increasing order of equivalent weights of MnCl₂ in these conversions is
1. I<II<III<IV
2. IV=III<II=I
3. IV<III<II<I
4. Equivalent weight is independent of oxidation number
What is the equivalent mass of IO₄⁻ when it is converted into I₂ in acid medium?
1. M/6
2. M/7
3. M/5
4. M/4
The reaction 3CIO⁻(aq) → ClO₃⁻(aq) + 2Cl⁻(aq) is an example of
1. Oxidation reaction
2. Reduction reaction
3. Disproportionation reaction
4. Decomposition reaction
Which of the following species does not show disproportionation reaction?
1. ClO₄⁻
2. ClO₂⁻
3. ClO₃⁻
4. All of these
Which is the intramolecualr oxidation-reduction reaction?
1. 2KClO₃ → 2KCl + 3O₂
2. (NH₄)₂Cr₂O₇ → N₂ + CrO₃ + 4H₂O
3. PCl₅ → PCl₃ + Cl₂
4. All of these
Based on the following reactions,
XeO₆⁴⁻(aq) + 2F⁻(aq) + 6H⁺(aq) → XeO₃(g) + F₂(g) + 3H₂O(l) (∆G⁰<0)
It can be concluded that
1. Oxidising power of F⁻ is greater than that of XeO₆⁴⁻
2. It is not a redox reaction
3. It is a disproportionation reaction
4. Oxidising power of XeO₆⁴⁻ is greater than that of F⁻
Equivalent weight of N₂ in the change
N₂ → NH₃ is,
1. 28/6
2. 28
3. 28/2
4. 28/3
What is the equivalent weight of NH₃ in the given reaction?
3CuO + 2NH₃ → 3Cu + N₂ + 3H₂O
1. 17
2. 17/4
3. 17/2
4. 17/3