Class 12 Chemistry

Chapter 3 – Electrochemistry

Magical Series Assignment 4

 

Q.1.     Calculate the potential for half–cell containing 0.10 M K₂Cr₂O₇(aq), 0.20 M Cr³⁺(aq) and 1.0 × 10^–4 M H(aq)· The half-cell reaction is:

Cr₂O₇^2–(aq) + 14H⁺(aq) + 6e^– → 2Cr³⁺(aq) + 7H₂O(l)

and the standard electrode potential is given as E^o = 1.33 V.

Q.2.     For the cell,

Zn(s) | Zn²⁺ (2 M) || Cu²⁺ (0.5 M) | Cu(s)

(a) Write equation for each half–reaction.

(b) Calculate the cell potential at 25°C

Given: E^o_Zn2+/Zn = –0.76 V; E^o_Cu2+/Cu = +0.34 V.

Q.3.     Calculate the equilibrium constant, K for the reaction at 298 K,

Zn(s) + Cu²⁺(aq) ⇌ Zn²⁺(aq) + Cu(s)

Given: ∆G^o = –212.300 kJ mol^–1, E^o_Zn2+/Zn = –0.76 V; E^o_Cu2+/Cu = +0.34 V.

Q.4.     A copper–silver cell is set up. The copper ion concentration is 0.10 M. The concentration of silver ion is not known. The cell potential when measured was 0.422 V. Determine the concentration of silver ions in the cell. Given: E^o_Ag+/Ag = +0.80 V, E^o_Cu2+/Cu = + 0.34 V

Q.5.     A voltaic cell is set up at 25°C with the following half cells:

Ag⁺(0.001 M) | Ag and Cu²⁺(0.10 M) | Cu

What would be the voltage of this cell? (E^o_cell = 0.46 V)

Q.6.     A voltaic cell is set up at 25°C with the following half–cells:

Al | Al³⁺(0.001 M) and Ni | Ni²⁺(0.50 M)

Calculate the cell voltage. [E^o_Ni2+/Ni = –0.25 V, E^o_Al3+/Al = –1.66 V]

Q.7.     Calculate the equilibrium constant for the reaction,

Fe(s) + Cd²⁺(aq) → Fe²⁺(aq) + Cd(s)

Given: [E^o_Cd2+/Cd = – 0.40 V, E^o_Fe2+/Fe = –0.44 V]

Q.8.     One half–cell in a voltaic cell is constructed from a silver wire dipped in silver nitrate solution of unknown concentration. Its other half–cell consists of a zinc electrode dipping in 1.0 M solution of Zn(NO₃)₂. A voltage of 1.48 V is measured for this cell. Use this information to calculate the concentration of silver nitrate solution used.

[E^o_Zn2+/Zn = –0.76 V, E^o_Ag+/Ag = +0.80 V]

Q.9.     Calculate e.m.f. and ∆G for the following cell

Mg(s) | Mg²⁺(0.001 M) || Cu²⁺(0.0001 M) | Cu(s)

E^o_Mg2+/Mg = –2·37 V, E^o_Cu2+/Cu = +0.34 V

Q.10.     Calculate the standard electrode potential of Ni²⁺/Ni electrode if emf of the cell

Ni(s) | Ni²⁺(0.01 M) || Cu²⁺(0.1 M) | Cu(s)

is 0.059 V. [Given: E^o_Cu2+/Cu = + 0.34 V]

Q.11.     Calculate the cell emf and ∆Go for the cell reaction at 25°C

Zn(s) | Zn²⁺(0.1 M) || Cd²⁺(0.01 M) | Cd(s)

Given: E^o_Zn2+/Zn = –0.763 V, E^o_Cd2+/Cd = –0.403 V

1 F = 96,500 C mol^–1, R = 8.314 J K^–1 mol^–1.

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