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Fuel Cells

The efficienc...

Question

The efficiency of fuel cell is given by the expression, $η$ is:

η = - \frac{n F E_{c e l l}}{Δ H} \times 100

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η = - \frac{n F E_{c e l l}}{Δ S} \times 100

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η = - \frac{n F E_{c e l l}}{Δ A} \times 100

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None of the above

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Solution

The correct option is A $η = - \frac{n F E_{c e l l}}{Δ H} \times 100$
Efficiency of fuel cell is $η = - \frac{n F E_{c e l l}}{Δ H} \times 100$ .

The thermodynamic efficiency of the fuel cell is the ratio of the electrical free energy to the enthalpy change of the reaction.

$η = \frac{Δ G}{Δ H} \times 100$

Also, $Δ G = - n F E_{c e l l}$

Hence, option A is correct.

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Similar questions

Q. The temperature coefficient of a spontaneous cell is

(\frac{δ E}{δ T})_{P}

. Choose the correct statements.

Q. Electrical energy produced by a reversible electrochemical cell is given by the free energy decrease

(- Δ G)

of the reaction occurring in the cell. According to Gibbs- Helmholtz equation, decrease in free energy is given by

- Δ G = - Δ H - T {[\frac{δ (Δ G)}{δ T}]}_{P}

where

- Δ H

is the decrease in enthalpy of the cell reaction at constant pressure. EMF of the cell,

E = \frac{- Δ H}{n F} + T {[\frac{δ E}{δ T}]}_{P}

. By measuring the emf of the cell and its temperature co-efficient, thermodynamic quantities like

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and

Δ S

can be determined. Standard emf of the cell is related to equilibrium constant of the cell reaction as

E^{0} = \frac{2.303 R T l o g k}{n F}

.

EMF of the cell,

\begin{matrix} A & A^{2 +} & B^{+} & B (S) & (a q) & (a q) & (s) 1 M & 0.1 M \end{matrix}

is found to be 1.475 Volt. The equilibrium constant of the cell reaction at

25^{\circ}

C is (approximately)

Q. When two half cells X and Y combined then the standard cell potential of cell is.

Q. Electrical energy produced by a reversible electrochemical cell is given by the free energy decrease

(- Δ G)

of the reaction occurring in the cell. According to Gibbs- Helmholtz equation, decrease in free energy is given by

- Δ G = - Δ H - T {[\frac{δ (Δ G)}{δ T}]}_{P}

where

- Δ H

is the decrease in enthalpy of the cell reaction at constant pressure. EMF of the cell,

E = \frac{- Δ H}{n F} + T {[\frac{δ E}{δ T}]}_{P}

. By measuring the emf of the cell and its temperature co-efficient, thermodynamic quantities like

Δ H, Δ G

and

Δ S

can be determined. Standard emf of the cell is related to equilibrium constant of the cell reaction as

E^{0} = \frac{2.303 R T l o g k}{n F}

.

The standard emf of the cell,

\begin{matrix} Z n & Z n^{+ 2} & F e^{+ 3} F e^{+ 2} (S) & (a q) & (a q) (a q) \end{matrix}

Pt at

25^{\circ}

C is 1.53 V and at

50^{\circ}

C is 1.55 V. The value of

Δ S^{\circ}

for the overall reaction is

Q. Electrical energy produced by a reversible electrochemical cell is given by the free energy decrease

(- Δ G)

of the reaction occurring in the cell. According to Gibbs- Helmholtz equation, decrease in free energy is given by

- Δ G = - Δ H - T {[\frac{δ (Δ G)}{δ T}]}_{P}

where

- Δ H

is the decrease in enthalpy of the cell reaction at constant pressure. EMF of the cell,

E = \frac{- Δ H}{n F} + T {[\frac{δ E}{δ T}]}_{P}

. By measuring the emf of the cell and its temperature co-efficient, thermodynamic quantities like

Δ H, Δ G

and

Δ S

can be determined. Standard emf of the cell is related to equilibrium constant of the cell reaction as

E^{0} = \frac{2.303 R T l o g k}{n F}

.

From the following values of electrode potentials,
(i)

(f u m a r a t e)^{2 -} + 2 H^{+} + 2 e^{-} \to (s u c c i n a t e)^{- 2}, E_{1}^{0} = 0.03 V

and
(ii)

(p y r u v a t e)^{-} + 2 H^{+} + 2 e^{-} \to (l a c t a t e)^{-}, E_{2}^{0} = - 0.18 V . C a l c u l a t e Δ G^{\circ}

for the reaction,

(f u m a r a t e)^{2 -} + (l a c t a t e)^{-} \to (s u c c i n a t e)^{- 2} + (p y r u v a t e)^{-}

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The efficiency of fuel cell is given by the expression, η is:

The correct option is A η=−nFEcellΔH×100 Efficiency of fuel cell is η=−nFEcellΔH×100.The thermodynamic efficiency of the fuel cell is the ratio of the electrical free energy to the enthalpy change of the reaction.η=ΔGΔH×100Also, ΔG=−nFEcellHence, option A is correct.

The efficiency of fuel cell is given by the expression, $η$ is: