Calculate ∆ G ° for the reaction Zn s + Cu 2 + aq → Zn 2 + aq + Cu s Given: E ° for Zn 2 + / Zn = - 0 . 76 V E ° for Cu 2 + / Cu = + 0 . 34 V R = 8 . 314 JK - 1 mol - 1 F = 96500 C mol - 1

Given reaction is Zn s + Cu 2 + aq → Zn 2 + aq + Cu s We know that, E cell ° = E cathode ° - E anode ° E cell ° = 0 . 34 - - 0 . 76 E cell ° = 1 . 10 V The standard Gibbs free energy change is the energy change that occurs in going from the reactants to the products. It can be calculated by using the formula, ∆ G ° = - nFE cell ° ∆ G ° = - 2 × 1 . 10 × 96500 = - 212 . 3 kJ mol - 1

The cell in which the following reaction occurs: 2 F e 3 + a q + 2 I - a q → 2 F e 2 + a q + I 2 ( s ) has E c e l l 0 = 0.236 V at 298 K . Calculate the standard Gibbs energy and the equilibrium constant of the cell reaction.

Given E c e l l 0 = 0.236 V T = 298 K 2 Fe 3 + aq + 2 I - aq → 2 Fe 2 + aq + I 2 ( s ) Here, n = 2 and F = 96500 We know that: ∆ r G 0 = - n F E c e l l 0 = - 2 × 96500 × 0.236 = - 45 , 548 J m o l - 1 = - 45.54 k J m o l - 1 = - 45.54 × 10 3 J m o l - 1 Again, ∆ r G = ∆ r G 0 + 2.303 R T log ⁡ Q At equilibrium ∴ ∆ r G = 0 and Q = K c ∆ r G 0 = - 2.303 R T log ⁡ K c ⇒ log ⁡ K c = - ∆ r G 0 2.303 R T = - ( - 45.54 × 10 3 ) 2.303 × 8.314 × 298 = 7.981 ∴ K c = A n t i l o g 7.981 = 9.57 × 10 7

EASY

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How many $k J$ of energy is evolved, when a current of $2.00 A$ passes for $200 s$ under the potential of $230 V$ ?

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Important Questions on Electrochemistry

EASY

Chemistry>Physical Chemistry>Electrochemistry>Thermodynamics of Cell

The standard free energy change (in J) for the reaction

3 {Fe}^{2 +} (aq) + 2 Cr (s) \to 2 {Cr}^{3 +} (aq) + 3 Fe (s)

given

E_{{Fe}^{2 +} / Fe}^{0} = - 0 .44 V and E_{{Cr}^{3 +} / Cr}^{0} = - 0 .74 V

(F = 96500 C)

EASY

Chemistry>Physical Chemistry>Electrochemistry>Thermodynamics of Cell

The equilibrium constant of a

2

electron redox reaction at

298 K

3.8 \times 10^{- 3} .

The cell potential

E^{o} (in V)

and the free energy change

{ΔG}^{o} (in kJ {mol}^{-})

for this equilibrium respectively, are

EASY

Chemistry>Physical Chemistry>Electrochemistry>Thermodynamics of Cell

The standard electrode potential of

{Zn}^{2 +} / Zn is - 0 .76 V

and that of

{Cu}^{2 +} / Cu is 0 .34 V

. The emf

(V)

and the free energy change,

(in kJ {mol}^{- 1}),

respectively, for a Daniel cell will be

EASY

Chemistry>Physical Chemistry>Electrochemistry>Thermodynamics of Cell

The standard emf of a galvanic cell involving

2

moles of electrons in its redox reaction is

0.59 V

. The equilibrium constant for the redox reaction of the cell is:

HARD

Chemistry>Physical Chemistry>Electrochemistry>Thermodynamics of Cell

The standard electrode potential $E^{o}$ and its temperature coefficient $(\frac{dE}{dT})$ for a cell are $2 V$ and $- 5 {\times10}^{- 4} V K^{- 1}$ at $300 K$ , respectively. The reaction is $Zn (s) + {Cu}^{2 +} (aq) \to {Zn}^{2 +} (aq) + Cu (s)$ . The standard reaction enthalpy $(Δ_{r} H^{-})$ at $300 K$ in $m o l^{- 1}$ is

$[$ Use $R = 8 J K^{- 1} {mol}^{- 1}$ and $F =96,500 C {mol}^{- 1}]$

MEDIUM

Chemistry>Physical Chemistry>Electrochemistry>Thermodynamics of Cell

For a cell involving one electron

E_{c e l l}^{⊝} = 0.59 V

298 K

, the equilibrium constant for the cell reaction is:

[G i v e n t h a t \frac{2.303 R T}{F} = 0.059 V a t T = 298 K]

EASY

Chemistry>Physical Chemistry>Electrochemistry>Thermodynamics of Cell

What is the standard reduction potential

(E^{o})

for

{Fe}^{3 +} \to Fe ?

Given that:

{Fe}^{2 +} + 2 e^{-} \to Fe; E_{{Fe}^{2 +} / Fe}^{o} = - 0 .47 V

{Fe}^{3 +} + e^{-} \to {Fe}^{2 +}; E_{{Fe}^{3 +} / {Fe}^{2 +}}^{o} = + 0 .77 V

MEDIUM

Chemistry>Physical Chemistry>Electrochemistry>Thermodynamics of Cell

The emf of the following cell is $1.229 V$ at $298 K$ .

$Pt, H_{2} (1 atm) |H^{+} (1 M)| O_{2} (1 atm), Pt$

$H_{2} + \frac{1}{2} O_{2} ⇌ H_{2} O$

The standard free energy change for the cell reaction is________ $[F = 9.649 \times 10^{4} C {mol}^{- 1}]$

MEDIUM

Chemistry>Physical Chemistry>Electrochemistry>Thermodynamics of Cell

If the standard electrode potential for a cell is

2 V

300 K,

the equilibrium constant

(K)

for the reaction.

Zn (s) + {Cu}^{2 +} (aq) ⇌ {Zn}^{2 +} (aq) + Cu (s)

300 K

is approximately:

(R = 8 {JK}^{- 1} {mol}^{- 1}, F = 96000 C {mol}^{- 1})

EASY

Chemistry>Physical Chemistry>Electrochemistry>Thermodynamics of Cell

If the

E_{c e l l}^{o}

for a given reaction has a negative value, which of the following gives the correct relationship for the values of

∆ G^{o}

and

K_{e q}

MEDIUM

Chemistry>Physical Chemistry>Electrochemistry>Thermodynamics of Cell

Given

E_{{Mn}^{+ 7} | {Mn}^{+ 2}}^{\circ} = 1.5 V

and

E_{{Mn}^{+ 4} | {Mn}^{+ 2}}^{\circ} = 1.2 V

, then

E_{{Mn}^{+ 7} / {Mn}^{+ 4}}^{\circ}

HARD

Chemistry>Physical Chemistry>Electrochemistry>Thermodynamics of Cell

Calculate $∆ G^{°}$ for the reaction $Zn (s) + {Cu}^{2 +} (aq) \to {Zn}^{2 +} (aq) + Cu (s)$

Given:

$E^{°} for {Zn}^{2 +} / Zn = - 0.76 V E^{°} for {Cu}^{2 +} / Cu = + 0.34 V R = 8.314 {JK}^{- 1} {mol}^{- 1} F = 96500 C {mol}^{- 1}$

MEDIUM

Chemistry>Physical Chemistry>Electrochemistry>Thermodynamics of Cell

For a reaction,

A + B^{2 +} ⟶ B + A^{2 +}

, at

25^{0} C E^{0} = 0.2955 V

. The value of

K_{eq}

MEDIUM

Chemistry>Physical Chemistry>Electrochemistry>Thermodynamics of Cell

For the cell reaction

$2 F e^{3 +} (a q) + 2 I^{-} (a q) \to 2 F e^{2 +} (a q) + I_{2} (a q)$

$E_{c e l l}^{0} = 0.24 V$ at $298 K .$ The standard Gibbs energy $(Δ_{r} G^{o})$ of the cell reaction is:

[Given that Faraday constant $F = 96500 C m o l^{- 1}$ ]

HARD

Chemistry>Physical Chemistry>Electrochemistry>Thermodynamics of Cell

Question Image

The value of $E_{1}^{o}$ is

MEDIUM

Chemistry>Physical Chemistry>Electrochemistry>Thermodynamics of Cell

The standard e.m.f. of the cell, $Cd (s) |{CdCl}_{2} (aq) (0.1 M)| | AgCl (s) | Ag (s)$ in which the cell reaction is $Cd (s) + 2 AgCl (s) ⟶ 2 Ag (s) + {Cd}^{2 +} (aq) + 2 {Cl}^{-} (aq)$ is $0.6915 V$ at $0 ° C$ and $0.6753 V$ at $25 ° C$ . The enthalpy change of the reaction at $25 ° C$ is

MEDIUM

Chemistry>Physical Chemistry>Electrochemistry>Thermodynamics of Cell

The standard free energy change for the cell reaction

Z n_{(s)} + C u_{(a q)}^{2 +} \to Z n_{(a q)}^{2 +} + C u_{(s)}

(E_{Z n^{2 +} / Z n} ° = - 0.76 V, E_{C u^{2 +} / C u} ° = + 0.34 V, 1 F = 96500 {Cmol}^{- 1})

EASY

Chemistry>Physical Chemistry>Electrochemistry>Thermodynamics of Cell

Given the standard potentials

E^{o} (\frac{C u^{2 +}}{C u})

and

E^{o} (\frac{C u^{+}}{C u})

0.340 V

and

0.522 V

respectively, the value of

E^{o} (\frac{C u^{2 +}}{C u^{+}})

MEDIUM

Chemistry>Physical Chemistry>Electrochemistry>Thermodynamics of Cell

The emf of a particular voltaic cell with the cell reaction,

{Hg}_{2}^{2 +} + H_{2} ⇌ 2 Hg + 2 H^{+}

, is

0.65 V

. What is the maximum electrical work of this cell when

0 .5 g

H_{2}

is consumed?

HARD

Chemistry>Physical Chemistry>Electrochemistry>Thermodynamics of Cell

The cell in which the following reaction occurs:

2 F e_{}^{3 +} (a q) + 2 I_{}^{-} (a q) \to 2 F e_{}^{2 +} (a q) + I_{2} (s)

has

E_{c e l l}^{0} = 0.236 V

298 K .

Calculate the standard Gibbs energy and the equilibrium constant of the cell reaction.

How many kJ of energy is evolved, when a current of 2.00 A passes for 200 s under the potential of 230 V?

Important Questions on Electrochemistry

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How many $k J$ of energy is evolved, when a current of $2.00 A$ passes for $200 s$ under the potential of $230 V$ ?