CBSE Class 12 · 2006 · Delhi; also All India 2006 Compartment · Redox Reactions and ElectrochemistryLong Answer

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i) Define the terms specific conductance and molar conductivity for solutions of electrolytes.
ii) Write the cell formulation and calculate the standard cell potential for the galvanic cell in which the following reaction takes place:

2Cr (s) + 3C d^{2 +} (aq) ⟶ 2C r^{3 +} (aq) + 3Cd (s)

Calculate

Δ_{r} G^{\circ}

for the above reaction.
(Given:

E_{C r^{3 +} /Cr}^{\circ} = - 0.74

E_{C d^{2 +} /Cd}^{\circ} = - 0.40

V; 1 F = 96500 C mol

^{- 1}

)

Solution

(i) Specific conductance (conductivity,

κ

): the conductance of a solution of unit length and unit cross-section — the conductance of a unit cube of solution; units S cm

^{- 1}

.
Molar conductivity (

Λ_{m}

): the conductance of the volume of solution containing one mole of electrolyte between electrodes of unit area a unit distance apart;

Λ_{m} = κ \times 1000/ C

, units S cm

^{2}

mol

^{- 1}

.
(ii) Cell formulation:

Cr (s) ∣ C r^{3 +} (aq) ∣∣ C d^{2 +} (aq) ∣ Cd (s)

E_{ce l l}^{\circ} = - 0.40 - (- 0.74) = 0.34 V, n = 6

Δ_{r} G^{\circ} = - 6 \times 96500 \times 0.34

Δ_{r} G^{\circ} = - 1.97 \times 1 0^{5} J = - 196.9 kJ mo l^{- 1}

CBSE Class 12 Board · 2006 · Delhi; also All India 2006 Compartment · Subjective

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CBSE Class 12 · 2006 · Delhi; also All India 2006 Compartment · Redox Reactions and ElectrochemistryLong Answer

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