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Lead storage battery.

E cell =  E⁰ -0.0591/n x log 0.16/(2 x 10^-3 ) ²

= 1.05 -0.0591/2 x log 16 x 10⁴ /4

=0.91 volt

Electrode : The arrangement consisting of a metal rod dipping in an aqueous solution or molten electrolyte containing ions and conduct electric current due to oxidation or reduction half reactions occurring on its surface is called an electrode.

The electrodes which take part in the reactions are called active electrodes while those which do not take part in the reactions are called inert electrodes.

Iron will corrode faster as the oxidation potential of Fe is higher than that of tin.

(a) Anode : An electrode of an electrochemical cell, at which oxidation half reaction occurs due to the loss of electrons from some species is called an anode.

(b) Cathode : An electrode of an electrochemical cell at which reduction half reaction occurs due to gain of electrons by some species is called a cathode.

There are two types of electrochemical cells as follows : 

1. Electrolytic cells 

2. Voltaic or galvanic cells.

(1) Electrolytic cell : An electrochemical cell in which a non-spontaneous chemical reaction is forced to occur by passing direct electric current into the solution from the external source and where electrical energy is converted into chemical energy is called an electrolytic cell. 

E.g. voltameter, electrolytic cell for deposition of a metal.

(2) Voltaic or galvanic cell : An electrochemical cell in which a spontaneous chemical reaction occurs producing electricity and where a chemical energy is converted into an electrical energy is called voltaic cell or galvanic cell. 

E.g. Daniell cell, dry cell, lead storage battery, fuel cells, etc.

Galvanic or voltaic cell : An electrochemical cell which is used to produce electrical energy by a spontaneous chemical reaction inside it is called an electrochemical cell. In this chemical energy is converted into electrical energy. 

Example : Daniell cell.

Instead of coating more reactive metal or iron, the use of such metal is made as sacrificial anode. Connecting Iron with more reactive metal with the help of a wire.

Half cell or Electrode : It is a metal electrode dipped in the electrolytic solution and capable of establishing oxidation reduction equilibrium with one of the ions of electrolyte solution and develop electrode potential. 

E.g. Zn in ZnSO₄ solution.

(1) Degree of dissociation is 2.5% and pH of solution is 1.3 

Correct option  (1, 2)

Explanation:

The metallic conduction is due to the presence of electrons in the metal and electrolytic conduction is due to the movement of ions in the solution.

The functions of a salt bridge are :

1. It maintains the electrical contact between the two electrode solutions of the half cells.

2. It prevents the mixing of electrode solutions.

3. It maintains the electrical neutrality in both the solutions of two half cells by a flow of ions.

4. It eliminates the liquid junction potential.

The functions of a salt bridge are :

• It maintains the electrical contact between the two electrode solutions of the half cells. 
• It prevents the mixing of electrode solutions. 
• It maintains the electrical neutrality in both the solutions of two half cells by a flow of ions.
• It eliminates the liquid junction potential.

1. Λ_m = \(\frac{1000k}{M}\)

2.  ^Λ° CH₃COOH = ^Λ° CH₃COONa +  ^Λ° HCl  -  ^Λ° Nacl

= 91 + 425.9 – 126.4

= 390.5 Ω^-1 cm² mol^-1

Correct option (2, 3, 4) 

Explanation:

For the electrolyte A_x B_y

n-factor = xy 

Λ_M = (xy) Λ_eq

Only 1^st option is correct & others are incorrect option.

Functions of Salt Bridge :

1. Salt Bridge maintains electrical neutrality in solutions. 

2. It completes circuit internally. 

These are of 4 types :

(1) Dry cell (primary cell)

(2) Mercury cell/Button Cell

(3) Lead storage battery

(4) Fuel cell

1. The quantity ℓ/A is called cell constant.

A = Area of cross section of the electrodes.

ℓ = distance of separation of two electrodes.

2. Specific conductance = Cell constant × Conductance

3. Cell constant = Specific conductance × Resistance

= 0.0075 ohm 1 cm^-1 × 100 ohm = 0.75 cm^-1

1. The above equation is correct.

2. Kohlrausch’s law. Molar conductance at infinite dilution of an electrolyte is the sum of the molar ionic conductivities at infinite dilution of the cations and anions present in the solution.

3. The application of this law :

• To find the molar conductivity at infinite dilution (Λ°m) of weak electrolytes.
• To find the degree of dissociation (α) of weak electrolytes. α = \(\frac{Λ_m}{Λ^0_m} \)
• To determine the dissociation constant of weak electrolytes. Ka = \(\frac{c^2\alpha}{1-\alpha}\)  

(i) To compare the relative oxidizing and reducing powers- A chemical species with higher value of E° will be stronger oxidizing agent and a chemical species with more – ve E° will be stronger reducing agent.

(ii) To compare the relative activities of metals- A metal with more –ve E° value will be more reactive 

(iii) To calculate the E°cell of given cell- 

E⁰_cell = E°_cathode - E°_anode or E°_cell = E°_RHS - E°_LHS 

N.B. - E° for SHE is taken 0 (Zero) 

(iv) To predict whether a metal will displace hydrogen from its compound or not- All the chemical species which have –ve E° value will displace hydrogen from its compounds.

M → Mn⁺ + ne^- (electron lost is gained by H⁺ ion to undergo reduction and H₂ is formed) 

Usefulness of Nernst equation to calculate E_cell at different conc. And temp. 

Definition of strong electrolyte, weak electrolyte, limiting molar conductivity.

1. In H₂ – O₂ fuel cell, hydrogen and oxygen are bubbled through porous carbon electrodes into concentrated aqueous NaOH solution, which acts as the electrolyte. The electrode reactions are,

Anode : 2H₂(g) + 4 OH^-(aq) → 4 H₂O(l) + 4\(\bar e\)

Cathode : O₂(g) + 2 H₂O(l) + 4\(\bar e\) → 4 OH^-(aq)

Overall reaction : 2H₂(g) + O₂(g) → 2 H₂O(l)

2. The advantages of fuel cells over other cells 

• They are pollution free. 
• More efficient than conventional methods. 
• Runs continuously as long as the reactants are supplied. 
• Electrodes are not affected. 

Advantages of Fuel Cells : 

1. As works as long as we supply Hydrogen & oxygen gas.

2. It causes no pollution 

3. Its efficiency is 70% 

4. Its By product (Water) is also useful.

(a) (i) These are devices for converting chemical energy into electrical energy. The decrease in free energy in a spontaneous chemical process appears as electrical energy. e.g., Daniell oeil.
(ii) (1) Fuel cells are pollution free.

(2) Fuel cells are highly efficient (about 70%) compared to thermal plants (about 40%)

(3) Fuel cells run continuously as long as the reactants are supplied. 

(b) At cathode:

O₂(g) + 2H₂O(l) + 4e → 4OH(aq)

At anode:

2H₂(g) + 4OH(aq) → 4H₂O(l)

Advantages of fuel cell:

• Long lasting, 
• More efficient, 
• Eco friendly, 
• Give useful by products

It is a process of eating away of metals on their surfaces, it is an unwanted process as it results in loss of mass of metals. In this process metal surface reacts with atmospheric oxygen to form a layer of oxide. It is an electrochemical reaction.

Lower the reduction potential, easily if gets oxidized hence greater is the reducing power, therefore the increasing order of reducing power is Ag < Hg < Cr < mg < K.