CBSE Class 12 · 2009 · Delhi · Redox Reactions and ElectrochemistryLong Answer

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a) State the relationship among the cell constant of a cell, the resistance of the solution in the cell and the conductivity of the solution.
b) A voltaic cell is set up at 25°C with the following half-cells: Al | Al

^{3 +}

(0.001 M) and Ni | Ni

^{2 +}

(0.50 M). Calculate the cell voltage.
(

E_{N i^{2 +} /Ni}^{\circ} = - 0.25

E_{A l^{3 +} /Al}^{\circ} = - 1.66

Answer: (a) κ = cell constant / R. (b) E_cell ≈ 1.46 V

Solution

(a)

κ = \frac{cell constant}{R} (G^{*} = \frac{l}{A})

(b) Al is the anode; cell reaction: 2Al + 3Ni

^{2 +} \to

2Al

^{3 +}

+ 3Ni,

n = 6

E_{ce l l}^{\circ} = - 0.25 - (- 1.66) = 1.41 V

Nernst equation:

E_{ce l l} = 1.41 - \frac{0.059}{6} lo g \frac{( 1 0 ^{- 3} ) ^{2}}{( 0.50 ) ^{3}} = 1.41 - \frac{0.059}{6} lo g (8 \times 1 0^{- 6})

= 1.41 - 0.00983 \times (- 5.097) = 1.41 + 0.050

E_{ce l l} = 1.46 V

CBSE Class 12 Board · 2009 · Delhi · Subjective

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CBSE Class 12 · 2009 · Delhi · Redox Reactions and ElectrochemistryLong Answer

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