A certain metal salt solutions is electrolysed in series with a silver coulometer. The weights of silver and the metal deposited are 0.5094 g and 0.2653 g. Calculate the valency of the metal if its atomic weight is nearly that of silver. 

(1) 1                                                 

(2) 2

(3) 3                                                 

(4) 4

Subtopic:  Faraday’s Law of Electrolysis |
 79%
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The temperature coefficient, of the emf is dεdT= – 0.00065 volt. deg-1 for the cell Cd|CdCl21m| AgClsAg at 25°C. Calculate the entropy change S298K,  for the cell reaction,Cd + 2AgCl Cd++ + 2Cl+ 2Ag

(1)  105.5 JK-1   

(2)  150.2 JK-1

(3)  75.5 JK-1

 (4)  125.5 JK-1

Subtopic:  Electrode & Electrode Potential |
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The reduction potential of a half-cell consisting of a Pt electrode immersed in 1.5 M Fe2+and 0.015 M Fe3+ solution at 25°C is EFe+3, Fe+2°=+0.770 v.

(1) 0.652 V                                                   

(2) 0.88 V

(3) 0.710 V                                                   

(4) 0.850 V

Subtopic:  Nernst Equation |
 59%
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In a concentration cell, Zn/Zn2+ (1.0 M) || Zn2+ (0.15 M)/Zn as the cell discharges,

(1) reaction proceeds to the right

(2) the two solutions approach each other in concentration

(3) no reaction takes place

(4) water gets decomposed

Subtopic:  Electrode & Electrode Potential |
 57%
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In a half-cell containing [Tl3+] = 0.1 M and [Tl+ ] = 0.01 M, the cell potential is – 1.2496 V for the reaction Tl+ Tl3+ + 2e-  The standard reduction potential of the Tl+ /Tl3+ couple at 25°C is

(1) 1.44 V                                          

(2) 0.61 V

(3) 2.44 V                                          

(4) 1.22 V

Subtopic:  Nernst Equation |
 72%
From NCERT
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Given cell: 

Pt(s)|H2(g)(P = 1 atm)| CH3COOH(0.1 M), HCl(0.1 M) || KCl(aq)|Hg2Cl2(s)|Hg

EMF of the cell is found to be 0.045 V at 298 K and the temperature coefficient is 3.4×10-4 V K-1. The cell entropy change of the following cell is : 

[Given Ka CH3COOH = 10-5  M]

1. 70.8 J K−1 mol−1                      

2. 65.2 J K−1 mol−1

3. 79.2 J K−1 mol−1                  

4. 83.5 J K−1 mol−1

Subtopic:  Relation between Emf, G, Kc & pH |
 62%
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A dilute solution of H2 SO4 was electrolysed by passing a current of 2 amp. The time required for formation of 0.5 mole of oxygen is

(1) 26.8 hours                                    

(2) 13.4 hours

(3) 6.7 hours                                      

(4) 28.6 hours

Subtopic:  Faraday’s Law of Electrolysis |
From NCERT
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The standard reduction potentials for Mn3+/Mn2+ and MnO2 /Mn3+ couples in acid medium at 25°C are 1.50 V and 1.00 V respectively. The following reaction:

2Mn3+ + 2H2O  Mn2+ + MnO2 + 4H+ is

(1) reversible                                             

(2) non-spontaneous

(3) spontaneous                                         

(4) irreversible

Subtopic:  Electrode & Electrode Potential |
 75%
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In the following electrochemical cell, M|M+ || X-|X, the standard reduction potentials are E°M+/M= 0.52 V and E°X/X- = 0.42 V at 25°C. Which one of the following statements is correct ?

(1) M + X  M+ + X- is spontaneous              

(2) M+ + X- M + X is spontaneous

(3) Ecell = 0.77 V                                              

(4) Ecell=  0.77 V

Subtopic:  Electrode & Electrode Potential |
 66%
From NCERT
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1If a 100 mL solution of 0.1M HBr is titrated using a very concentrated solution of NaOH, when the conductivity (specific conductance) of the solution at the equivalence point will 3e (assume volume change is negligible due to addition of NaOH). Calculate your answer in terms of 10-1Sm-1,

Given °Na+=8×10-3Sm2mol-1 °Br-=4×10-3S m2 mol-1

(1) 6                               

(2) 12

(3) 15                             

(4) 24

Subtopic:  Conductance & Conductivity |
 75%
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