Ncert Solutions Chemistry Class 12th

This is a Matching Type Questions as classified in NCERT Exemplar

Ans:  (i)The reaction occurring at Lechlanche cells are 

At anode: Zn→Zn²⁺ + 2e⁻

At cathode: MnO₂ + NH₄⁺ + e⁻→MnO (OH)+NH₃

(ii)Ni−Cd is rechargeable. So it has a longer lifetime.

(iii) Energy in the fuel cell is due to the combustion process. It converts combustion energy into electrical energy 2H₂ + O₂→2H₂O

(iv) Mercury cells don't involve any solution and are used in hearing aids.

Hence, the answer is:

(i)-d; (ii)-c; (iii)-a, e; (iv)-b

This is a Matching Type Questions as classified in NCERT Exemplar

Ans:   (i)Conductivity k is defined as k = $°$

(ii)Molar conductivity is given by Λ_m = $*\mathit{T}$

(iii)Degree of dissociation  is given by $\frac{\mathbf{\Lambda }\mathbf{m}}{{\mathbf{\Lambda }}^0\mathbf{m}}$ ? = $\mathit{\alpha }$

(iv)Charge $\frac{\mathit{K}}{\mathit{C}}$  is the product of current and time $\mathit{}\mathit{Q}$  = I $\frac{\mathit{G}}{\mathit{R}}$

Hence, the answer is:

(i)-d; (ii)-c; (iii)-b; (iv)-a

This is a Matching Type Question as classified in NCERT Exemplar

(i)- (a) ; (ii)- (b) ; (iii)- (b); (iv)- (a)

 A zero-order reaction is one in which the reactant concentrations do not change over time and the rate of concentration remains constant.

A first-order reaction is one in which the rate of the reaction is linearly proportional to the concentration of only one ingredient. In other terms, a first-order reaction is a chemical reaction whose rate is determined by changes in only one of the reactants' concentration.

This is a Matching Type Questions as classified in NCERT Exemplar

Ans: (i) The cell reaction of a lead storage battery is as follows;

Pb + PbO₂ + 2H₂SO₄→2H₂SO₄ + 2H₂O

At cathode:PbO₂ (s)+SO₄²⁻ (aq)+2e⁻→2PbSO₄ (s) + 2H₂O (l)

At anode:Pb (s)+SO₄²⁻ (aq)→PbSO₄ (s)+2e⁻

Therefore Pb is the anode and PbO₂ is cathode

(ii)Mercury cell doesn't contain ions so it gives steady potential.

(iii)Fuel cells have maximum efficiency as they produce energy due to the combustion reaction of fuel.

(iv)Rusting is prevented by galvanization.

Hence, the answer is:

(i)-d ; (ii)-c ; (iii)-a ; (iv)-b

This is a Matching Type Questions as classified in NCERT Exemplar

Ans: (i)On dilution, the number of ions per unit volume increases so the molar conductivity increases with dilution.

(ii) E $°$ _cell is an intensive property as it is not dependent on the amount or mass of the substance. 

(iii) k is conductivity or be precise specific conductivity which depends on the number of ions

(iv) ΔrG_cell is an extensive property as it depends on the amount of substance or number of particles in the solution.

Hence, the answer is:

(i)-d ; (ii)a ; (iii)-b ; (iv)-c

This is a Matching Type Questions as classified in NCERT Exemplar

Ans: (i)The unit of  Λm is Scm²mol⁻¹

(ii) The unit of E_cell is m⁻¹

(iii) The unit of k is Scm⁻¹

(iv)The unit of  G∗ is m⁻¹

Hence, the answer is:

(i)-c ; (ii)-d ; (iii)-a ; (iv)-b

This is a Multiple Choice Questions as classified in NCERT Exemplar

Correct options: A and D

The pace of a reaction that is directly proportional to the concentration of the reacting substance is known as a first order reaction. 

Y=mn

k = $\frac{2.303}{\mathrm{t}}\mathrm{}$ log  $\frac{\mathbf{ }\mathbf{a}}{\mathbf{a}-\mathbf{x}\mathbf{ }}$

t = $\frac{2.303}{\mathrm{k}}\mathrm{}$ log $\frac{\mathbf{ }\mathbf{a}}{\mathbf{a}-\mathbf{x}\mathbf{ }}$

x= a- $\frac{\mathbf{a}}{2}$

x= $\frac{\mathbf{a}}{2}$

t $\raisebox{1ex}{$1$}\!\left/ \!\raisebox{-1ex}{$2$}\right.\mathbf{}$ _{= $\frac{2.303}{\mathrm{k}}\mathrm{}$} log $\frac{\mathbf{ }\mathbf{a}}{\mathbf{a}-\frac{\mathbf{a}}{2}\mathbf{ }}$   

$\frac{2.303}{\mathrm{k}}$ log2

= $\frac{0.693}{\mathrm{k}}$

This is a Multiple Choice Questions as classified in NCERT Exemplar

Correct options: A and D

A Zero order reaction = [R] =  ( - k)t +  [R]₀

y = (m *  ) + c

x = t (time)

y =  [R]concentration

Slope (m) =  - k

Intercept (c) =  [R]₀

  $\frac{\left. [\mathbf{R}\right]\mathbf{ }-\mathbf{ }{\left. [\mathbf{R}\right]}_0}{\mathbf{t}}$ =  - k

$\frac{\left. [\mathbf{R}\right]\mathbf{ }-\mathbf{ }{\left. [\mathbf{R}\right]}_0}{\mathbf{t}}$ =  - kt^o

Rate ∝ t⁰

This is a Multiple Choice Questions as classified in NCERT Exemplar

Ans: Correct Option: Option (ii, iii)

In the given representation of the cell, the left side represents the oxidation half cell and the right side of the cell represents the reduction half cell

The electrode at which oxidation occurs is called anode and oxidation of magnesium occurs at anode so magnesium is the anode.

Similarly, the electrode at which the reduction occurs is called the cathode, and the reduction of copper occurs at the cathode.

The cell reaction is as follows

Mg + Cu²⁺→Mg²⁺+ Cu