# Write the Nernst equation and emf of the following cells at 298 K:(i) Mg(s)|Mg2+ (0.001M)||Cu2+ (0.0001 M)|Cu(s)(ii) Fe(s)|Fe2+ (0.001M)||H+ (1M)|H2(g)(1bar)| Pt(s)(iii) Sn(s)|Sn2+ (0.050 M)||H+ (0.020 M)|H2(g) (1 bar)|Pt(s)(iv) Pt(s)|Br2(l)|Br–(0.010 M)||H+ (0.030 M)| H2(g) (1 bar)|Pt(s).

Ecell = ?

(i) Mg + Cu2 + Mg2 + + Cu (n = 2)

E0Cu2 + /Cu + = 0.34V

E0Mg2 + /Mg = - 2.37 V

E0cell = E0R - E0L

E0cell = 0.34 - ( - 2.37) Equation 1

Using Nernst equation, we get,

Equation 2

Substituting Equation 1 in equation 2, we get,

Ecell = 0.34 - ( - 2.37) -

= 2.71 -

= 2.71 - 0.02955

Ecell = 2.68 V

The e.m.f of the cell, Ecell is 2.68 V

ii) Fe + 2H + Fe2 + + H2 (n = 2)

E0H + /H2 = 0 V

E0Fe2 + /Fe = - 0.44 V

E0cell = E0R - E0L

E0cell = 0 - ( - 0.44) Equation 1

Using Nernst equation, we get,

Equation 2

Substituting Equation 1 in equation 2, we get,

Ecell = 0 - ( - 0.44) -

= 0.44 -

= 0.44 - 0.0887

Ecell = 0.5287 V

The e.m.f of the cell, Ecell is 0.5287 V

iii) Sn + 2H + Sn2 + + H2 (n = 2)

E0H + /H2 = 0 V

E0Sn2 + /Sn = - 0.14V

E0cell = E0R - E0L

E0cell = 0 - ( - 0.14) Equation 1

Using Nernst equation, we get,

Equation 2

Substituting Equation 1 in equation 2, we get,

Ecell = 0 - ( - 0.14) -

= 0.14 -

= 0.14 - 0.0295×2.0969

Ecell = 0.08 V

The e.m.f of the cell, Ecell is 0.08 V

iv) 2Br - + 2H + Br2 + H2 (n = 2)

E0H + /H2 = 0 V

E0Br2/Br - = 1.08V

E0cell = E0R - E0L

E0cell = 0 - (1.08) Equation 1

Using Nernst equation, we get,

Equation 2

Substituting Equation 1 in equation 2, we get,

Ecell = 0 - (1.08) -

= - 1.08 -

= - 1.08 - 0.208

Ecell = 1.288 V

The e.m.f of the cell, Ecell is 1.288 V

Rate this question :

How useful is this solution?
We strive to provide quality solutions. Please rate us to serve you better.
Related Videos
Electrochemistry - 0763 mins
Nernst Equation - Learn the Concept33 mins
Difference between electrochemical and electrolysis45 mins
Electrochemistry - 0464 mins
Electrochemistry - 0621 mins
Master Concept of Oxidising and Reducing agent42 mins
Practice Questions on faraday's law44 mins
Qualitative Aspect of Electrolysis58 mins
Quiz | Nernst Equation - 0341 mins
Electrochemistry - 0560 mins
Try our Mini CourseMaster Important Topics in 7 DaysLearn from IITians, NITians, Doctors & Academic Experts
Dedicated counsellor for each student
24X7 Doubt Resolution
Daily Report Card
Detailed Performance Evaluation
view all courses