Chemistry NCERT Exemplar Solutions Class 11th Chapter Eight: Overview, Questions, Preparation

On the basis of standard electrode potential values, suggest which of the following reactions would take place? (Consult the book for E V value). 

(i) Cu + Zn²⁺ → Cu²⁺ + Zn

(ii) Mg + Fe²⁺ → Mg²⁺ + Fe

(iii) Br2 + 2Cl^– → Cl₂ + 2Br^–

 (iv) Fe + Cd²⁺ → Cd + Fe²⁺

Find out the oxidation number of chlorine in the following compounds and arrange them in increasing order of oxidation number of chlorine. NaClO₄ , NaClO₃ , NaClO, KClO₂ , Cl₂O₇ , ClO₃ , Cl₂O, NaCl, Cl₂ , ClO₂ . Which oxidation state is not present in any of the above compounds?

Which method can be used to find out strength of reductant/oxidant in a solution? Explain with an example.

The reaction

Cl₂ (g) + 2OH^– (aq) → ClO^– (aq) + Cl^– (aq) + H₂O (l)

represents the process of bleaching. Identify and name the species that bleaches the substances due to its oxidising action.

PbO and PbO₂ react with HCl according to following chemical equations :

2PbO + 4HCl → 2PbCl₂ + 2H₂O

PbO₂ + 4HCl → PbCl₂ + Cl₂ + 2H₂O

Why do these compounds differ in their reactivity?

Write balanced chemical equation for the following reactions:

(i) Permanganate ion (MnO₄ ^– ) reacts with sulphur dioxide gas in acidic medium to produce Mn₂⁺ and hydrogensulphate ion. (Balance by ion electron method).

(ii) Reaction of liquid hydrazine (N₂H₄ ) with chlorate ion (ClO₃^– ) in basic medium produces nitric oxide gas and chloride ion in gaseous state. (Balance by oxidation number method)

(iii) Dichlorine heptaoxide (Cl₂O₇ ) in gaseous state combines with an aqueous solution of hydrogen peroxide in acidic medium to give chlorite ion (ClO₂^– ) and oxygen gas. (Balance by ion electron method)

Calculate the oxidation number of each sulphur atom in the following compounds:

(a) Na₂S₂O₃

(b) Na₂S₄O₆

_{(c) Na₂SO₃}

_{(d) Na2SO4}

Balance the following equations by the oxidation number method

(i) Fe²⁺ + H⁺ + Cr₂^2–O₇ → Cr₃⁺ + Fe₃⁺ + H₂O

(ii) I₂ + NO₃^–  → NO₂ + IO₃ ^–

(iii) I ₂ + S₂O₃^2–  → I^– + S₄O₆^2–

^{(iv) MnO₂ + C₂ O₄2– → Mn₂+ + CO₂}

Identify the redox reactions out of the following reactions and identify the oxidising and reducing agents in them. 

(i) 3HCl(aq) + HNO₃ (aq) → Cl₂ (g) + NOCl (g) + 2H₂O (l )

(ii) HgCl₂ (aq) + 2KI (aq) → HgI₂ (s) + 2KCl (aq)

(iii) Fe₂O₃ (s) + 3CO (g) →   2Fe (s) + 3CO₂ (g)

(iv) PCl₃ (l) + 3H₂O (l) → 3HCl (aq) + H₃ PO₃ (aq)

(v) 4NH₃ + 3O₂ (g) → 2N₂ (g) + 6H₂O (g)

Balance the following ionic equations

(i) Cr₂ O₇^2– + H⁺ + I^– → Cr³⁺ + I₂ + H₂O

(ii) Cr₂ O₇^2– + Fe₂⁺ + H⁺ → Cr₃⁺ + Fe₃⁺ + H₂O

(iii) MnO₄^–  + SO₃^2– + H⁺ → Mn₂⁺ + SO₄^2–  + H₂O

(iv) MnO₄^–  + H⁺ + Br^– → Mn₂⁺ + Br² + H₂O

Which of the following is not an example of redox reaction?

(i) CuO + H₂ → Cu + H₂O

(ii) Fe₂O₃ + 3CO → 2Fe + 3CO₂

(iii) 2K + F₂ → 2KF

(iv) BaCl₂ + H₂ SO₄ → BaSO₄ + 2HCl

The more positive the value of EV , 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.

EV values: Fe³+/Fe²⁺ = + 0.77; I₂ (s)/I^– = + 0.54;

Cu₂⁺/Cu = + 0.34; Ag⁺/Ag = + 0.80V

(i) Fe³⁺

(ii) I₂ (s)

(iii) Cu²⁺

(iv) Ag⁺

EᶱV  values of some redox couples are given below. On the basis of these values choose the correct option.

EᶱV values : Br₂ /Br^– = + 1.90; Ag⁺ /Ag(s) = +0.80

Cu₂₊/Cu(s) = + 0.34; I₂ (s)/I^– = + 0.54

(i) Cu will reduce Br^–

(ii) Cu will reduce Ag

(iii) Cu will reduce I^–

(iv) Cu will reduce Br₂

Using the standard electrode potential, find out the pair between which redox reaction is not feasible.

EᶱV values : Fe³⁺/Fe²⁺ = + 0.77; I2 /I^– = + 0.54

Cu²⁺/Cu = + 0.34; Ag⁺ /Ag = + 0.80 V

(i) Fe³⁺ and I^–

(ii) Ag⁺ and Cu

(iii) Fe³⁺ and Cu

(iv) Ag and Fe³⁺

Thiosulphate reacts differently with iodine and bromine in the reactions given below: 

2S₂O₃^2– + I₂ → S₄O₆^2– + 2I^– S₂O₃^2–+ 2Br₂ + 5H₂O → 2SO₄^2– + 2Br^– + 10H

Which of the following statements justifies the above dual behaviour of thiosulphate?

(i) Bromine is a stronger oxidant than iodine.

(ii) Bromine is a weaker oxidant than iodine.

(iii) Thiosulphate undergoes oxidation by bromine and reduction by iodine in these reactions.

(iv) Bromine undergoes oxidation and iodine undergoes reduction in these reactions.

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?

(i) The oxidation number of hydrogen is always +1.

(ii) The algebraic sum of all the oxidation numbers in a compound is zero.

(iii) An element in the free or the uncombined state bears oxidation number zero.

(iv) In all its compounds, the oxidation number of fluorine is – 1

In which of the following compounds, an element exhibits two different oxidation states.

(i) NH₂OH

(ii) NH₄NO₃

(iii) N₂H₄

(iv) N₃H

Which of the following arrangements represent increasing oxidation number of the central atom?

(i) CrO₂ ^– , ClO₃ ^– , CrO₄ ^2– , MnO₄ ^–

(ii) ClO₃ ^– , CrO₄^2– , MnO₄ ^– , CrO₂

(iii) CrO₂ ^– , ClO₃ ^– , MnO₄ ^– , CrO₄ ^2–

(iv) CrO₄ ^2– , MnO₄ ^– , CrO₂ ^– , ClO₃^–

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?

(i) 3d¹ 4s²

(ii) 3d³ 4s²

(iii) 3d⁵ 4s¹

(iv) 3d⁵ 4s²

Identify disproportionation reaction

(i) CH₄ + 2O₂ → CO₂ + 2H₂O

(ii) CH₄ + 4Cl₂ → CCl₄ + 4HCl

(iii) 2F₂ + 2OH^– → 2F^– + OF₂ + H₂O

(iv) 2NO₂ + 2OH^– → NO₂ ^– + NO₃ ^– + H₂O

Which of the following elements does not show disproportionation tendency?

(i) Cl

(ii) Br

(iii) F

(iv) I

In the following questions two or more options may be correct.

Which of the following statement(s) is/are not true about the following decomposition reaction.

2KClO₃ → 2KCl + 3O₂

(i) Potassium is undergoing oxidation

(ii) Chlorine is undergoing oxidation

(iii) Oxygen is reduced

(iv) None of the species are undergoing oxidation or reduction

Identify the correct statement (s) in relation to the following reaction:

Zn + 2HCl → ZnCl₂ + H₂

(i) Zinc is acting as an oxidant

(ii) Chlorine is acting as a reductant

(iii) Hydrogen ion is acting as an oxidant

(iv) Zinc is acting as a reductant

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.

(i) 3s ¹

(ii) 3d ¹ 4s ²

(iii) 3d² 4s²

(iv) 3s² 3p³

Identify the correct statements with reference to the given reaction.

P₄ + 3OH^– + 3H₂O → PH₃ + 3H₂PO₂

(i) Phosphorus is undergoing reduction only.

(ii) Phosphorus is undergoing oxidation only.

(iii) Phosphorus is undergoing oxidation as well as reduction.

(iv) Hydrogen is undergoing neither oxidation nor reduction.

Which of the following electrodes will act as anodes, when connected to Standard Hydrogen Electrode?

(i) Al/Al₃⁺                             Eᶱ V = –1.66

(ii) Fe/Fe₂⁺                           Eᶱ V= – 0.44

(iii) Cu/Cu₂⁺                        Eᶱ V= + 0.34

(iv) F₂ (g)/2F^– (aq)               Eᶱ V= + 2.87

In the following questions a statement of assertion (A) followed by a statement of reason (R) is given. Choose the correct option out of the choices given below each question.

Assertion (A) : Among halogens fluorine is the best oxidant.

Reason (R) : Fluorine is the most electronegative atom.

(i) Both A and R are true and R is the correct explanation of A.

(ii) Both A and R are true but R is not the correct explanation of A.

(iii) A is true but R is false.

(iv) Both A and R are false.

Assertion (A): In the reaction between potassium permanganate and potassium iodide, permanganate ions act as oxidising agent. 

Reason (R): Oxidation state of manganese changes from +2 to +7 during the reaction. 

(i) Both A and R are true and R is the correct explanation of A. 

(ii) Both A and R are true but R is not the correct explanation of A. 

(iii)A is true but R is false. 

(iv) Both A and R are false.

Assertion (A) : The decomposition of hydrogen peroxide to form water and oxygen is an example of disproportionation reaction. 

Reason (R) : The oxygen of peroxide is in –1 oxidation state and it is converted to zero oxidation state in O² and –2 oxidation state in H₂O.

(i) Both A and R are true and R is the correct explanation of A.

(ii) Both A and R are true but R is not the correct explanation of A.

(iii) A is true but R is false.

(iv) Both A and R are false.

Assertion (A) : Redox couple is the combination of oxidised and reduced form of a substance involved in an oxidation or reduction half cell.

(i) Both A and R are true and R is the correct explanation of A.

(ii) Both A and R are true but R is not the correct explanation of A.

(iii) A is true but R is false.

(iv) Both A and R are false

The total number of amines among the following which can be synthesized by Gabriel synthesis is………………

Sucrose hydrolyses in acid solution into glucose and fructose following first order rate law with a half – life of 3.33 h at 25°C. After 9h, the fraction of sucrose remaining is f. The value of log₁₀ $\left(\frac{1}{f}\right)$  is………………….× 10^-2. (Rounded off to the nearest integer)

[Assume: In 10 = 2.303, In2 = 0.693]

The solubility product of Pbl₂ is 8.0 × 10^-9. The solubility of lead iodide in 0.1 molar solution of lead nitrate is x × 10^-6 mol/L. The value of x is…………………… (Rounded off to the nearest integer)

[Given  $\sqrt[]{2}=1.41]$

The formula of a gaseous hydrocarbon which requires 6 times of its own volume of O₂ for complete oxidation and produces 4 times its own volume of CO₂ is C_xH_y. The value of y is…………….

1.86g of aniline completely reacts to form acetanilide. 10% of the product is lost during purification. Amount of acetanilide obtained after purification (in g) is…………………..× 10^-2.

The volume occupied by 4.75 of acetylene gas at 50°C and 740 mmHg pressure is………………….L (Rounded off to the nearest integer)

[Given R = 0.0826L atm K^-1 mol^-1]

The magnitude of the change in oxidizing power of the $Mn{O}_4^{-}/M{n}^{2+}$  couple is x × 10^-4 V, if the H⁺ concentration is decrease from 1M to 10^-4M at 25°C (Assume concentration of   $Mn{O}_4^{-}$ and Mn²⁺ to be same on change in H⁺ concentration). The value of x is………………… (Rounded off to the nearest integer)

[Given : $\frac{2.303RT}{F}=0.059$ ]

Assuming ideal behaviour, the magnitude of log K for the following reaction at 25°C is x × 10^-1. The value of x is ………………… (integer answer)

3HC  $\equiv C{H}_{\left(g\right)}?C_6{H}_{6\left(I\right)}$

[Given : ${\Delta }_{f}G°\left(HC\equiv CH\right)$  = -2.04 × 10⁵J mol^-1 ; ${\Delta }_{f}G°\left(C_6{H}_6\right)=-1.24\times 10^{5}Jmo{l}^{-1}:$ R = 8.314 JK^-1mol^-1]

C₆H₆ freezes at 5.5°C. The temperature at which a solution of 10g of C₄H₁₀ in 200g of C₆H₆ freeze is……………….. °C (The molal freezing point depression constant of C₆H₆ is 5.12°C/m)

Among the following allotropic forms of sulphur, the number of allotropic forms, which will show paramagnetism is…………………….

(a) α - sulphur                     (b) β - sulphur                 (c) S₂ - form

The stepwise formation of ${{\left[Cu{\left(N{H}_3\right)}_4\right]}^2}^{+}$  is given below:

$C{u}^{2+}+N{H}_3\stackrel{k_1}{?}{\left[Cu\left(N{H}_3\right)\right]}^{2+}$            

${\left[Cu\left(N{H}_3\right)\right]}^{2+}+N{H}_3\stackrel{k_2}{?}{\left[Cu{\left(N{H}_3\right)}_2\right]}^{2+}$        

  ${\left[Cu{\left(N{H}_3\right)}_2\right]}^{2+}+N{H}_3\stackrel{k_3}{?}{\left[Cu{\left(N{H}_3\right)}_3\right]}^{2+}$          

${\left[Cu{\left(N{H}_3\right)}_3\right]}^{2+}+N{H}_3\stackrel{k_4}{?}{\left[Cu{\left(N{H}_3\right)}_4\right]}^{2+}$            

The value of stability constants k₁, k₂, k₃ and k₄ are  $10^4,1.58\times 10^3,5\times 10^{2}and10^2$ respectively.

The overall equilibrium constants for dissociation of   ${\left[Cu{\left(N{H}_3\right)}_4\right]}^{2+}isx\times 10^{-12}.$ The value of x is________ (Rounded off to the nearest integer)

For the reaction A_(g) ® B_(g) the value of the equilibrium constant at 300K and 1 atm is equal to 100.0 The value of for the reaction at 300K and 1 atm in J mol^-1 is -xR, where x is_________.

(Rounded off to the nearest integer)

[R = 8.31 J mol^-1 K^-1 and In 10 = 2.3]

At 1990K and 1 atm pressure, there are equal number of Cl₂ molecules and Cl atoms in the reaction mixture. The value of K_P for the reaction $?$ Cl_2(g)  2Cl_(g) under the above conditions is x × 10^-1. The value of x is______ (Rounded off to the nearest integer)

When 9.45g of ClCH₂COOH is added to 500ml. of water, its freezing point drops by 0.5°C. The dissociation constant of ClCH₂ COOH is x × 10^-3. The value of x is__________ (Rounded off to the nearest integer)

$\left[k_{f\left(H_{2}O\right)}=1.86Kkgmo{l}^{-1}\right]$         

The reaction of sulphur in alkaline medium is given below

$S_{8\left(s\right)}+aO{H^{-}}_{\left(aq\right)}\to b{S^{2-}}_{\left(aq\right)}+c{S}_2{O_3^{2-}}_{\left(aq\right)}+d{H}_2{O}_{\left(I\right)}$            

The values of ‘a’ is____________. (Integer answer)

4.5g of compound A (MW = 90) was used to make 250 mL of its aqueous solution. The molarity of the solution in M is × 10^-1. The value of x is_________ (Rounded off to the nearest integer)

A proton and a Li³⁺ nucleus are accelerated by the same potential. If ${\lambda }_{Li}and{\lambda }_P$  denote the de Brogle wavelength of Li³⁺ and proton respectively, then the value of $\frac{{\lambda }_{Li}}{{\lambda }_P}isx\times 10^{-1}.$  The value of x is_________ (Rounded off to the nearest integer)           [Mass of Li³⁺ = 8.3 mass of proton]

The coordination number of an atom in a body- centred cubic structure is___________.

 [Assume that the lattice is made up of atoms]

Gaseous cyclobutene isomerizes to butadiene in a first order process which has ‘k’ value of 3.3 × 10^-4 s^-1 at 153°C. The time in minutes it takes for the isomerization to proceed 40% to completion at this temperature is______ (Rounded off the nearest integer)

The volume (in  $\mathrm{m}\mathrm{L}$ ) of $0.1\mathrm{N}\mathrm{N}\mathrm{a}\mathrm{O}\mathrm{H}$  required to neutralise $10\mathrm{m}\mathrm{L}$ of $0.1\mathrm{N}$  phosphinic acid is

If   $250{\mathrm{c}\mathrm{m}}^3$ of an aqueous solution containing $0.73\mathrm{g}$ of a protein $\mathrm{A}$  is isotonic with one litre of another aqueous solution containing $1.65\mathrm{g}$  of a protein $\mathrm{B}$ , at $298\mathrm{K}$ , the ratio of the molecular masses $A$ of  and $B$  is   $\times {10}^{-2}$ (to the nearest integer). 

An acidic solution of dichromate is electrolyzed for 8 minutes using $2\mathrm{A}$  current. As per the following equation ${\mathrm{C}\mathrm{r}}_2{\mathrm{O}}_7^{2-}+14{\mathrm{H}}^{+}+6{\mathrm{e}}^{-}\to 2{\mathrm{C}\mathrm{r}}^{3+}+7{\mathrm{H}}_2\mathrm{O}$   . The amount of ${\mathrm{C}\mathrm{r}}^{3+}$ obtained was $0.104\mathrm{g}$   . The efficiency of the process (in %) is (Take: $\mathrm{F}=96000\mathrm{C}$   , At. Mass of chromium $=52$    )

$6.023\times {10}^{22}$ molecules are present in $10\mathrm{g}$ of a substance '  $x$ '. The molarity of a solution containing $5\mathrm{g}$  of substance ' $\mathrm{x}$  ' in   $2\mathrm{L}$ solution is $\times {10}^{-3}$ .                 

If the solubility product of AB₂ is 3.20 × 10⁻¹¹ M³, then the solubility of AB₂ in pure water is _____ × 10⁻⁴ mol L⁻¹. [Assuming that neither kind of ion reacts with water]

For Freudlich adsorption isotherm, a plot of log(x/m) ( y-axis) and log p (x-axis) gives a straight line. The intercept and slope for the line is 0.4771 and 2, respectively. The mass of gas adsorbed per gram of adsorbent if the initial pressure is 0.04 atm, is _____ × 10?? g. (log 3 = 0.4771)

A solution of phenol in chloroform when treated with aqueous NaOH gives compound P as a major product. The mass percentage of carbon in P is (to the nearest integer) _____. (Atomic mass: C = 12; H = 1; O = 16 )

The rate of a reaction decreased by 3.555 times when the temperature was changed from 40°C to 30°C. The activation energy (in kJmol⁻¹ ) of the reaction is _____.