NCERT solutions for Chemistry - Part 1 and 2 [English] Class 11 chapter 8 - Redox Reactions [Latest edition]

Assign oxidation numbers to the underlined element in the following species:

 NaH₂PO₄

Assign oxidation numbers to the underlined element in the following species:

NaHSO₄

Assign oxidation numbers to the underlined element in the following species:

H₄P₂O₇

Assign oxidation numbers to the underlined elements in the following species:

K₂MnO₄

Assign oxidation numbers to the underlined elements in the following species:

CaO₂

Assign oxidation numbers to the underlined elements in the following species:

NaBH₄ 

Assign oxidation numbers to the underlined elements in the following species:

H₂S₂O₇

Assign oxidation numbers to the underlined elements in the following species:

KAl(SO₄)₂.12 H₂O

What are the oxidation numbers of the underlined elements in the following and how do you rationalise your results?

KI₃

What are the oxidation numbers of the underlined elements in the following and how do you rationalise your results?

H₂S₄O₆

What is the oxidation numbers of the underlined elements in the following and how do you rationalise your results?

 Fe₃O₄

What are the oxidation numbers of the underlined elements in the following and how do you rationalise your results?

CH₃CH₂OH

What is the oxidation numbers of the underlined elements in the following and how do you rationalise your results?

CH₃COOH

Justify that the following reaction is redox reaction:

\[\ce{CuO(s) + H2(g) → Cu(s) + H2O(g)}\]

Justify that the following reaction is redox reaction:

\[\ce{Fe2O3(s) + 3CO(g) → 2Fe(s) + 3CO2(g)}\]

Justify that the following reaction is redox reaction:

\[\ce{4BCl3(g) + 3LiAlH4(s) → 2B2H6(g) + 3LiCl(s) + 3 AlCl3(s)}\]

Justify that the following reaction is redox reaction:

\[\ce{2K(s) + F2(g) → 2K+F– (s)}\]

Justify that the following reaction is redox reaction:

\[\ce{4 NH3(g) + 5 O2(g) → 4NO(g) + 6H2O(g)}\]

Fluorine reacts with ice and results in the change: \[\ce{H2O(s) + F2(g) → HF(g) + HOF(g)}\]

Justify that this reaction is a redox reaction.

Calculate the oxidation number of sulphur, chromium and nitrogen in H₂SO₅, `"Cr"_2"O"_7^(2-)` and `"NO"_3^-`. Suggest structure of these compounds. Count for the fallacy.

Write the formulae for the following compound:

Mercury(II) chloride

Write the Formulae for the Following Compound:

Nickel(II) Sulphate

Write formulas for the following compound:

Tin(IV) oxide

Write the formulae for the following compound:

Thallium(I) sulphate

Write the Formulae for the Following Compound:

Iron(III) Sulphate

Write the Formulae for the Following Compound:

Chromium(III) Oxide

Suggest a list of the substances where carbon can exhibit oxidation states from –4 to +4 and nitrogen from –3 to +5.

While sulphur dioxide and hydrogen peroxide can act as oxidising as well as reducing agents in their reactions, ozone and nitric acid act only as oxidants. Why?

Consider the reaction:

\[\ce{6 CO2(g) + 6H2O(l) → C6 H12O6(aq) + 6O2(g)}\]

Why it is more appropriate to write these reaction as:

\[\ce{6CO2(g) + 12H2O(l) → C6 H12O6(aq) + 6H2O(l) + 6O2(g)}\]

Also, suggest a technique to investigate the path of the redox reactions.

Consider the reaction:

\[\ce{O3(g) + H2O2(l) → H2O(l) + 2O2(g)}\]

Why it is more appropriate to write these reaction as:

\[\ce{O3(g) + H2O2 (l) → H2O(l) + O2(g) + O2(g)}\]

Also, suggest a technique to investigate the path of the redox reactions.

The compound AgF₂ is an unstable compound. However, if formed, the compound acts as a very strong oxidizing agent. Why?

Whenever a reaction between an oxidising agent and a reducing agent is carried out, a compound of lower oxidation state is formed if the reducing agent is in excess and a compound of higher oxidation state is formed if the oxidising agent is in excess. Justify this statement giving three illustrations.

How do you count for the following observations?

Though alkaline potassium permanganate and acidic potassium permanganate both are used as oxidants, yet in the manufacture of benzoic acid from toluene we use alcoholic potassium permanganate as an oxidant. Why? Write a balanced redox equation for the reaction.

How do you count for the following observations?

When concentrated sulphuric acid is added to an inorganic mixture containing chloride, we get colourless pungent-smelling gas HCl, but if the mixture contains bromide then we get red vapour of bromine. Why?

Identify the substance oxidised, reduced, oxidising agent and reducing agent for the following reaction:

\[\ce{2AgBr (s) + C6H6O2(aq) → 2Ag(s) + 2HBr (aq) + C6H4O2(aq)}\]

Identify the substance oxidised, reduced, oxidising agent and reducing agent for the following reaction:

\[\ce{HCHO(l) + 2[Ag (NH3)2]+(aq) + 3OH–(aq) → 2Ag(s) + HCOO–(aq) + 4NH3(aq) + 2H2O(l)}\]

Identify the substance oxidised, reduced, oxidising agent and reducing agent for the following reaction:

\[\ce{HCHO (l) + 2Cu^{2+}(aq) + 5 OH–(aq) → Cu2O(s) + HCOO–(aq) + 3H2O(l)}\]

Identify the substance oxidised, reduced, oxidising agent and reducing agent for the following reaction:

\[\ce{N2H4(l) + 2H2O2(l) → N2(g) + 4H2O(l)}\]

Identify the substance oxidised, reduced, oxidising agent and reducing agent for the following reaction:

\[\ce{Pb(s) + PbO2(s) + 2H2SO4(aq) → 2PbSO4(s) + 2H2O(l)}\]

Consider the reactions:

\[\ce{2S_2O_3^{(2-)}(aq) + l_2(S) -> S_4O_6^{(2-)}(aq) + 2l-(aq)}\]

\[\ce{S_2O_3^{(2-)}(aq) + 2Br_2(l) + 5H_2O(l) -> 2SO_4^{2-} (aq) + 4Br-(aq) + 10H+ (aq)}\]

Why does the same reductant, thiosulphate react differently with iodine and bromine?

Justify giving reactions that among halogens, fluorine is the best oxidant and among hydrohalic compounds, hydroiodic acid is the best reductant.

Why does the following reaction occur?

\[\ce{XeO^{4-}_6 (aq) + 2F- (aq) + 6H+ (aq) -> XeO3(g) + F_2(g) + 3H_2O(l)}\]

What conclusion about the compound Na₄XeO₆ (of which `"XeO"_6^(4+)` is a part) can be drawn from the reaction.

Consider the reactions:

1. \[\ce{H3PO2(aq) + 4 AgNO3(aq) + 2 H2O(l) → H3PO4(aq) + 4Ag(s) + 4HNO3(aq)}\]
2. \[\ce{H3PO2(aq) + 2CuSO4(aq) + 2 H2O(l) → H3PO4(aq) + 2Cu(s) + H2SO4(aq)}\]
3. \[\ce{C6H5CHO(l) + 2[Ag (NH3)2]+(aq) + 3OH–(aq) → C6H5COO–(aq) + 2Ag(s) + 4NH3 (aq) + 2 H2O(l)}\]
4. \[\ce{C6H5CHO(l) + 2Cu^{2+}(aq) + 5OH–(aq) → No change observed}\]

What inference do you draw about the behaviour of Ag⁺ and Cu²⁺ from these reactions?

Balance the following redox reactions by ion-electron method:

1. \[\ce{MnO-_4 (aq) + I– (aq) → MnO2 (s) + I2(s) (in basic medium)}\]
2. \[\ce{MnO-_4 (aq) + SO2 (g) → Mn^{2+} (aq) + HSO-_4  (aq) (in acidic solution)}\]
3. \[\ce{H2O2 (aq) + Fe^{2+} (aq) → Fe^{3+} (aq) + H2O (l) (in acidic solution)}\]
4. \[\ce{Cr_2O^{2-}_7 + SO2(g) → Cr^{3+} (aq) + SO^{2-}_4 (aq) (in acidic solution)}\]

Balance the following equation in basic medium by ion-electron method and oxidation number methods and identify the oxidising agent and the reducing agent.

\[\ce{P4(s) + OH–(aq) —> PH3(g) + HPO^–_2(aq)}\]

Balance the following equation in the basic medium by ion-electron method and oxidation number methods and identify the oxidising agent and the reducing agent.

\[\ce{N2H4(l) + ClO^-_3 (aq) → NO(g) + Cl–(g)}\]

Balance the following equation in basic medium by ion-electron method and oxidation number methods and identify the oxidising agent and the reducing agent.

\[\ce{Cl_2O_{7(g)} + H_2O_{2(aq)} -> ClO-_{2(aq)} + O_{2(g)} + H+_{(aq)}}\]

What sorts of informations can you draw from the following reaction ?

\[\ce{{(CN)}_{2(g)} + 2OH-_{(aq)} -> CN-_{(aq)} + CNO-_{(aq)} + H_2O_{(l)}}\]

The Mn³⁺ ion is unstable in solution and undergoes disproportionation to give Mn²⁺, MnO₂, and H⁺ ion. Write a balanced ionic equation for the reaction.

Consider the elements: Cs, Ne, I and F

Identify the element that exhibits only negative oxidation state.

Consider the elements: Cs, Ne, I and F.

Identify the element that exhibits only postive oxidation state.

Consider the elements: Cs, Ne, I and F

Identify the element that exhibits both positive and negative oxidation states.

Consider the elements : Cs, Ne, I and F

Identify the element which exhibits neither the negative nor does the positive oxidation state.

Chlorine is used to purify drinking water. Excess of chlorine is harmful. The excess of chlorine is removed by treating with sulphur dioxide. Present a balanced equation for this redox change taking place in water.

Refer to the periodic table given in your book and now answer the following questions:

Select the possible non-metals that can show disproportionation reaction.

Refer to the periodic table given in your book and now answer the following question:

Select three metals that can show disproportionation reaction.

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?

Using the standard electrode potential, predict if the reaction between the following is feasible:

Fe³⁺(aq) and I^–(aq)

Using the standard electrode potential, predict if the reaction between the following is feasible:

Ag⁺(aq) and Cu(s)

Using the standard electrode potential, predict if the reaction between the following is feasible.

Fe³⁺(aq) and Cu(s)

Using the standard electrode potential, predict if the reaction between the following is feasible:

Ag(s) and Fe³⁺ (aq)

Using the standard electrode potential, predict if the reaction between the following is feasible:

 Br₂(aq) and Fe²⁺(aq)

Predict the product of electrolysis in the following:

An aqueous solution of AgNO₃ with silver electrodes.

Predict the product of electrolysis in the following:

An aqueous solution AgNO₃ with platinum electrodes.

Predict the product of electrolysis in the following:

A dilute solution of H₂SO₄ with platinum electrodes

Predict the product of electrolysis in the following:

An aqueous solution of CuCl₂ with platinum electrodes.

Arrange the following metals in the order in which they displace each other from the solution of their salts.

Al, Cu, Fe, Mg and Zn.

Given the standard electrode potentials,

K⁺/K = –2.93V, Ag⁺/Ag = 0.80V,

Hg²⁺/Hg = 0.79V

Mg²⁺/Mg = –2.37V. Cr³⁺/Cr = –0.74V

Arrange these metals in their increasing order of reducing power.

Depict the galvanic cell in which the reaction Zn(s) + 2Ag⁺(aq) → Zn²⁺(aq) + 2Ag(s) takes place, further show:

1. which of the electrode is negatively charged,
2. the carriers of the current in the cell, and
3. individual reaction at each electrode.