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Electrochemistry

Short Answer Type

261. Calculate the equilibrium constant for the reaction:
Zn + Cd²⁺ (aq) → Zn²⁺ (aq) + Cd (E°_cell = 0.36 V)

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262. Calculate the pH of the following half reactions: Pt. H₂ (1 atom) / HCl, E = 0.25 V.

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263. Electrolytic conductivity of 0.20 mol L^–1 solution of KCl at 298 k is 2.48 x 10^–2 ohm^–1cm^–1. Calculate its molar conductivity.

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264.

Calculate the molar conductivity at infinite dilution of acetic acid from the following data:
Λ^∞_m (HCl) = 426 ohm^–1 cm² mol^–1, Λ^∞_m CH₃COONa = 91 ohm^–1 cm² mol^–1 and Λ^∞_m(NaCl) = 126 ohm^–1 cm² mol^–1.

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265. Calculate the equilibrium constant of reaction at 25°C:
Ni(s) + Cu²⁺ (aq) → Cu(s) + Ni²⁺ (aq)
Given : E°_Ni2+/Ni = -0.25 V, E°_Cu2+/Cu = + 0.34 V, R = 8.314 J K^–1 mol^–1, F = 96500 C mol^–1.

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266. Calculate the standard free energy change for the reaction occuring in the cell:
Zn(s) | Zn²⁺ (1 M)|| Cu²⁺(1M) | Cu(s)
[Given E°_Zn2+/Zn = – 0.076 V, E°_Cu2+/Cu = + 0.34 V, F = 96500 C mol^–1]

162 Views

267.
Consider the cell Zn/Zn²⁺ (aq) (1.0 M) || Cu²⁺ (aq) (0.1 M) | Cu The standard reaction potentials are + 0.35 V for 2e^– + Cu²⁺ (aq) → Cu and – 0.763 V for 2e^– + Zn²⁺ (aq) → Zn
(i) Write down the cell reaction.
(ii) Calculate the emf of the cell.
(iii) Is the cell reaction spontaneous or not?

(I)Cell Reaction:
Oxidation: Zn----> Zn²⁺ +2e^-
Reduction: Cu²⁺ +2e^------> Cu
Therefore overall reaction
Zn +Cu²⁺ ------> Zn²⁺ +Cu
$E_{cell}^{0} = E_{\frac{{Cu}^{2 +}}{Cu}}^{0} - E_{\frac{{Zn}^{2 +}}{Zn}}^{0}$
(ii) $E_{cell}^{0}$ =+0.35-(-0.763)
=1.113 volts

(iii) Since EMF of cell is positive, it is a spontaneous reaction.

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268. The standard reaction potential for Cu²⁺/Cu is + 0.34 V. Calculate the reduction potential at pH = 14 for the above couple. Ksp of Cu(OH)₂ is 1.0 x 10^–19.

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269.

The standard reduction potential of the reaction at 25°C
2H₂O + 2e^– H₂(g) + 2OH^– is – 0.8277 V
Calculate equilibrium constant for the reaction
$2 H_{2} O ⇋ H_{3} O^{+} + {OH}^{-}$ at $25 ° C .$

124 Views

270. The resistance of a conductivity cell containing 0.01 M KCl solution at 298 K is 1500 Ω. What is the cell constant if conductivity of 0.001 M KCl solution at 298 K. is 1.46 x 10^–6 s cm^–1.

169 Views