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CHXII03:ELECTROCHEMISTRY

330315 With respect to $H_{2} - O_{2}$ fuel cell the correct statement is

1 Electrolyte used is pure

H_{2} O

2 Heat of combustion is directly converted to electrical energy.

3

O_{2}

gas gets oxidised to

O_{3}

in the cell.

4 Overall reaction in the cell is

2 H_{2} + O_{2} \to 2 H_{2} O

Explanation:

Fuel cell is an example of electrochemical cell in which chemical energy produced by the combustion of fuels converted to electrical energy. The electrode reactions given below:
$C a t h o d e : O_{2} + 2 H_{2} O + 4 e \to 4 O H^{-}$
$A n o d e : 2 H_{2} + 4 O H^{-} \to 4 H_{2} O + 4 e$
$O v e r a l l r e a c t i o n : 2 H_{2} + O_{2} \to 2 H_{2} O$

CHXII03:ELECTROCHEMISTRY

330295 Which of the following reaction is used to make a fuel cell?

1

Cd(s) + 2Ni(OH)_{3} (s) \to

CdO(s) + 2Ni(OH)_{2} (s) + H_{2} O(l)

2

Pb(s)  +  Pb O_{2} (s)  +  2 H_{2} S O_{4} (aq) \to

2PbS O_{4} (s) + 2 H_{2} O(l)

3

2 H_{2} (g)  + O_{2} (g) \to 2 H_{2} O (1)

4

\begin{matrix} 2Fe(s)  + O_{2} (g)  +  4 H^{+} (aq) \to \\ 2F e^{2  +} (aq)  +  2 H_{2} O (2) \end{matrix}

Explanation:

Cell which converts chemical energy of a fuel directly into electrical energy is called fuel cell, e.g. $H_{2} - O_{2}$ fuel cell. The net reaction taking place is
$2 H_{2} (g) + O_{2} (g) \to 2 H_{2} O (l)$

AIIMS - 2013

CHXII03:ELECTROCHEMISTRY

330296 Standard free energies of formation (in kJ/mol) at 298 K are $- 237 .2, - 394 .4 a n d - 8 .2$ for $H_{2} O (l), C O_{2} (g)$ and pentane(g), respectively. The value of $E_{c e l l}^{o}$ for the pentane-oxygen fuelcell is

1 0.0968 V

2 2.0968 V

3 1.0968 V

4 1.968 V

Explanation:

$C_{5} H_{12} + 80_{2} \to 5 C O_{2} + 6 H_{2} O$
$Δ G^{o} = 5 \times G^{o} C O_{2} + 6 \times G^{o} H_{2} {O - G}_{C_{5} H_{12}}^{o} {- 8 \times G}_{O_{2}}^{o}$
$= 5 \times (- 394 .4) + 6 \times (- 237 .2) + 8 .2$
$= - 3387 k J$
$Δ G^{o} = - n F E^{o}$
$- 3387 \times 1 0^{3} = - 32 \times E^{o} \times 96500$
$[5 C^{- 2.4} \to 5 (C^{4 +}) + 32 e]$
$n = 32$
$E^{o} = 1 .0968 V$ .

CHXII03:ELECTROCHEMISTRY

330315 With respect to $H_{2} - O_{2}$ fuel cell the correct statement is

1 Electrolyte used is pure

H_{2} O

2 Heat of combustion is directly converted to electrical energy.

3

O_{2}

gas gets oxidised to

O_{3}

in the cell.

4 Overall reaction in the cell is

2 H_{2} + O_{2} \to 2 H_{2} O

Explanation:

Fuel cell is an example of electrochemical cell in which chemical energy produced by the combustion of fuels converted to electrical energy. The electrode reactions given below:
$C a t h o d e : O_{2} + 2 H_{2} O + 4 e \to 4 O H^{-}$
$A n o d e : 2 H_{2} + 4 O H^{-} \to 4 H_{2} O + 4 e$
$O v e r a l l r e a c t i o n : 2 H_{2} + O_{2} \to 2 H_{2} O$

CHXII03:ELECTROCHEMISTRY

330295 Which of the following reaction is used to make a fuel cell?

1

Cd(s) + 2Ni(OH)_{3} (s) \to

CdO(s) + 2Ni(OH)_{2} (s) + H_{2} O(l)

2

Pb(s)  +  Pb O_{2} (s)  +  2 H_{2} S O_{4} (aq) \to

2PbS O_{4} (s) + 2 H_{2} O(l)

3

2 H_{2} (g)  + O_{2} (g) \to 2 H_{2} O (1)

4

\begin{matrix} 2Fe(s)  + O_{2} (g)  +  4 H^{+} (aq) \to \\ 2F e^{2  +} (aq)  +  2 H_{2} O (2) \end{matrix}

Explanation:

Cell which converts chemical energy of a fuel directly into electrical energy is called fuel cell, e.g. $H_{2} - O_{2}$ fuel cell. The net reaction taking place is
$2 H_{2} (g) + O_{2} (g) \to 2 H_{2} O (l)$

AIIMS - 2013

CHXII03:ELECTROCHEMISTRY

330296 Standard free energies of formation (in kJ/mol) at 298 K are $- 237 .2, - 394 .4 a n d - 8 .2$ for $H_{2} O (l), C O_{2} (g)$ and pentane(g), respectively. The value of $E_{c e l l}^{o}$ for the pentane-oxygen fuelcell is

1 0.0968 V

2 2.0968 V

3 1.0968 V

4 1.968 V

Explanation:

$C_{5} H_{12} + 80_{2} \to 5 C O_{2} + 6 H_{2} O$
$Δ G^{o} = 5 \times G^{o} C O_{2} + 6 \times G^{o} H_{2} {O - G}_{C_{5} H_{12}}^{o} {- 8 \times G}_{O_{2}}^{o}$
$= 5 \times (- 394 .4) + 6 \times (- 237 .2) + 8 .2$
$= - 3387 k J$
$Δ G^{o} = - n F E^{o}$
$- 3387 \times 1 0^{3} = - 32 \times E^{o} \times 96500$
$[5 C^{- 2.4} \to 5 (C^{4 +}) + 32 e]$
$n = 32$
$E^{o} = 1 .0968 V$ .

CHXII03:ELECTROCHEMISTRY

330315 With respect to $H_{2} - O_{2}$ fuel cell the correct statement is

1 Electrolyte used is pure

H_{2} O

2 Heat of combustion is directly converted to electrical energy.

3

O_{2}

gas gets oxidised to

O_{3}

in the cell.

4 Overall reaction in the cell is

2 H_{2} + O_{2} \to 2 H_{2} O

Explanation:

Fuel cell is an example of electrochemical cell in which chemical energy produced by the combustion of fuels converted to electrical energy. The electrode reactions given below:
$C a t h o d e : O_{2} + 2 H_{2} O + 4 e \to 4 O H^{-}$
$A n o d e : 2 H_{2} + 4 O H^{-} \to 4 H_{2} O + 4 e$
$O v e r a l l r e a c t i o n : 2 H_{2} + O_{2} \to 2 H_{2} O$

CHXII03:ELECTROCHEMISTRY

330295 Which of the following reaction is used to make a fuel cell?

1

Cd(s) + 2Ni(OH)_{3} (s) \to

CdO(s) + 2Ni(OH)_{2} (s) + H_{2} O(l)

2

Pb(s)  +  Pb O_{2} (s)  +  2 H_{2} S O_{4} (aq) \to

2PbS O_{4} (s) + 2 H_{2} O(l)

3

2 H_{2} (g)  + O_{2} (g) \to 2 H_{2} O (1)

4

\begin{matrix} 2Fe(s)  + O_{2} (g)  +  4 H^{+} (aq) \to \\ 2F e^{2  +} (aq)  +  2 H_{2} O (2) \end{matrix}

Explanation:

Cell which converts chemical energy of a fuel directly into electrical energy is called fuel cell, e.g. $H_{2} - O_{2}$ fuel cell. The net reaction taking place is
$2 H_{2} (g) + O_{2} (g) \to 2 H_{2} O (l)$

AIIMS - 2013

CHXII03:ELECTROCHEMISTRY

330296 Standard free energies of formation (in kJ/mol) at 298 K are $- 237 .2, - 394 .4 a n d - 8 .2$ for $H_{2} O (l), C O_{2} (g)$ and pentane(g), respectively. The value of $E_{c e l l}^{o}$ for the pentane-oxygen fuelcell is

1 0.0968 V

2 2.0968 V

3 1.0968 V

4 1.968 V

Explanation:

$C_{5} H_{12} + 80_{2} \to 5 C O_{2} + 6 H_{2} O$
$Δ G^{o} = 5 \times G^{o} C O_{2} + 6 \times G^{o} H_{2} {O - G}_{C_{5} H_{12}}^{o} {- 8 \times G}_{O_{2}}^{o}$
$= 5 \times (- 394 .4) + 6 \times (- 237 .2) + 8 .2$
$= - 3387 k J$
$Δ G^{o} = - n F E^{o}$
$- 3387 \times 1 0^{3} = - 32 \times E^{o} \times 96500$
$[5 C^{- 2.4} \to 5 (C^{4 +}) + 32 e]$
$n = 32$
$E^{o} = 1 .0968 V$ .

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