Which of these ions Cu+, Co3+, Fe2+ is stable in aqueous medium.

Given :E°Cu2+/Cu+ = 0.15 volt ; E°Cu+/Cu = 0.53 V ;E°Co3+/Co2+ = 1.82 V ;

Fe3+/Fe2+ = 0.77 V ;E°Fe2+Fe = –0.44 V ;E°O2,H+/H2O = 1.23 V

(1) Cu+, Co3+

(2) Co3+

(3) Cu+

(4) Co3+, Cu+, Fe2+

Subtopic:  Electrode & Electrode Potential |
 53%
From NCERT
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Select the correct statement if –

Mg2+/Mg = –2.4V, E°Sn4+/Sn2+ = 0.1 V, \(E_{MnO_{4}^{-}\, ,H^{+}\,/\,Mn^{+2} }^{\circ}\) = 1.5 V, \(E_{I_{2}\,/\,I^{-}}^{\circ} \)= 0.5 V

Here,

1. MnO4– is the strongest oxidizing agent and Mg is the strongest reducing agent.
2. Sn4+ + 2I Sn2+ + I2 is a spontaneous reaction.
3. Mg2+ + Sn2+ Mg + Sn4+ is a spontaneous reaction.
4. Weakest oxidizing agent is Sn4+ and weakest reducing agent is Mn2+.
Subtopic:  Electrode & Electrode Potential |
 76%
From NCERT
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The temperature coefficient of a standard Cd–cell is –5.0 × 10–5 Vk–1 whose emf at 25°C is 1.018 V. During the cell operation, the temperature will –

(1) increase

(2) decrease

(3) either

(4) remains constant

Subtopic:  Relation between Emf, G, Kc & pH |
 57%
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A cell Ag | Ag+ || Cu++ | Cu initially contains 2M Ag+ and 2M Cu++ ions. The charger in cell potential after the passage of 10 amp current for 4825 sec is:

(1) –0.000738 V

(2) –1.00738

(3) –0.0038 V

(4) none

Subtopic:  Faraday’s Law of Electrolysis |
From NCERT
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For the cell (at 298 K)

Ag(s) | AgCl(s) | Cl(aq) || AgNO3(aq) | Ag(s)

Which of the following is correct –

(1) The cell emf will be zero when [Ag+]a = [Ag+]c ([Ag+] in anodic compartment = [Ag+] in cathodic compartment)

(2) The amount of AgCl(s) precipitate in anodic compartment will decrease with the working of the cell.

(3) The concentration of [Ag+] = constant, in anodic compartment during working of cell.

(4) Ecell = E°Ag+ | Ag –E°Cl–|AgCl|Ag 0.0591log1[Cl]a

Subtopic:  Conductance & Conductivity |
From NCERT
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During electrolysis of conc. H2SO4, perdisulphuric acid (H2S2O8), and O2 form in equimolar amount. The amount of H2 that will form simultaneously will be : 

1. Thrice that of O2 in moles.

2. Twice that of O2 in moles.

3. Equal to that of O2 in moles.

4. Half of that of O2 in moles.

Subtopic:  Faraday’s Law of Electrolysis |
From NCERT
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Calculate the useful work of the reaction Ag(s) + 1/2Cl2(g) AgCl(s)

Given E°Cl2/Cl = + 1.36 V, E°AgCl/Ag,Cl = 0.22 V

If PCl2 = 1 atmand T = 298 K

(1) 110 kJ/mol

(2) 220 kJ/mol

(3) 55kJ/mol

(4) 1000 kJ/mol

Subtopic:  Relation between Emf, G, Kc & pH |
 65%
From NCERT
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Consider the cell Ag(s)|AgBr(s)|Br–(aq)||AgCl(s)|Cl–(aq)|Ag(s) at 25°C. The solubility product constants of AgBr & AgCl are respectively 5 × 10–13 & 1 × 10–10. For what ratio of the concentrations of Br& Clions would the emf of the cell be zero ?

(1) 1 : 200

(2) 1 : 100

(3) 1 : 500

(4) 200 : 1

Subtopic:  Nernst Equation |
From NCERT
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Acetic acid has Ka = 1.8 × 10–5 while formic acid had Ka = 2.1 × 10–4. What would be the magnitude of the emf of the cell

Pt(H2) 0.1M acetic acid+0.1M sodium acetate0.1M formic acid+0.1M sodium formate Pt(H2) at 25°C

(1) 0.0315 volt

(2) 0.0629 volt

(3) 0.0455 volt

(4) 0.0545 volt

Subtopic:  Nernst Equation |
 68%
From NCERT
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It is observed that the voltage of a galvanic cell using the reaction M(s) + xH+ Mx+ + x2 H2 varies linearly with the log of the square root of the hydrogen pressure and the cube root of the Mx+ concentration. The value of x is:

1. 2

2. 3

3. 4

4. 5

Subtopic:  Nernst Equation |
 62%
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