Consider the following cell reaction: 2 Fe ( s ) + O 2 ( g ) + 4 H + ( aq ) → 2 Fe 2 + ( aq ) + 2 H 2 O ( l ) ; E ° = 1 . 67 V and [ Fe 2 + ] = 10 - 3 M , p ( O 2 ) = 0 . 1 atm and pH = 3 . What is the cell potential at 25 ° C ?

Given : Standard electrode potential of iron E ° = 1 . 67 V Pressure of oxygen pO 2 = 0 . 1 atm pH = 3 Molarity = 10 - 3 M Solution : According to Nernst equation, E = E ° - 0 . 059 4 log [ Fe 2 + ] 2 pO 2 × [ H + ] 4 = 1 . 67 - 0 . 059 4 log ( 10 - 3 ) 2 0 . 1 × ( 10 - 3 ) 4 = 1 . 67 - 0 . 059 4 log 10 7 = 1 . 67 - 0 . 10 = 1 . 57 V Thus, the cell potential is 1 . 57 V

Consider the following cell reaction: 2 Fe ( s ) + O 2 ( g ) + 4 H + ( aq ) → 2 Fe 2 + ( aq ) + 2 H 2 O ( l ) ; E ° = 1 . 67 V and [ Fe 2 + ] = 10 - 3 M , p ( O 2 ) = 0 . 1 atm and pH = 3 . What is the cell potential at 25 ° C ?

Given : Standard electrode potential of iron E ° = 1 . 67 V Pressure of oxygen pO 2 = 0 . 1 atm pH = 3 Molarity = 10 - 3 M Solution : According to Nernst equation, E = E ° - 0 . 059 4 log [ Fe 2 + ] 2 pO 2 × [ H + ] 4 = 1 . 67 - 0 . 059 4 log ( 10 - 3 ) 2 0 . 1 × ( 10 - 3 ) 4 = 1 . 67 - 0 . 059 4 log 10 7 = 1 . 67 - 0 . 10 = 1 . 57 V Thus, the cell potential is 1 . 57 V

Calculate the potential for half-cell containing 0 . 10 M K 2 Cr 2 O 7 ( aq ) , 0 . 20 M Cr 3 + ( aq ) and 1 . 0 × 10 - 4 MH + ( aq ) . The half-cell reaction is Cr 2 O 7 2 - ( aq ) + 14 H + ( aq ) + 6 e - → 2 Cr 3 + ( aq ) + 7 H 2 O ( l ) and the standard electrode potential is given as E ° = 1 . 33 V .

Chemical equation: Cr 2 O 7 2 - ( aq ) + 14 H + ( aq ) + 6 e - → 2 Cr 3 + ( aq ) + 7 H 2 O ( l ) Given: Standard potential of cell E ° cell = 1 . 33 V Number of moles of electrons exchanged n = 6 Molarity of Cr 3 + = 0 . 2 M Molarity of Cr 2 O 7 2 - = 0 . 1 M Molarity of H + = 1 × 10 - 14 M Solution: Nernst equation is given by E cell = E ° - RT nF log Cr 3 + 2 Cr 2 O 7 2 - H + 14 E cell = 1 . 33 - 0 . 0591 6 log 0 . 20 2 0 . 1 10 - 4 14 E cell = 1 . 33 - 0 . 0591 6 log 4 × 10 - 55 E cell = 1 . 33 - 0 . 0591 6 log 4 + log 10 - 55 E cell = 1 . 33 - 0 . 0591 6 2 log 2 + 55 log 10 E cell = 1 . 33 - 0 . 0591 6 2 × 0 . 3010 + 55 E cell = 1 . 33 - 0 . 548 = 0 . 782 V Therefore, the potential for the half-cell containing the given electrolyte is 0 . 782 V .

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Consider the following cell reaction: $2 Fe (s) + O_{2} (g) + 4 H^{+} (aq) \to 2 {Fe}^{2 +} (aq) + 2 H_{2} O (l); E^{°} = 1.67 V$ and $[{Fe}^{2 +}] = 10^{- 3} M, p (O_{2}) = 0.1 atm$ and $pH = 3$ . What is the cell potential at $25^{°} C$ ?

Important Questions on Electrochemistry

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All In One ISC Chemistry Class 12>Chapter 3 - Electrochemistry>Chapter Practice>Q 45

Calculate the potential for half-cell containing

0.10 M K_{2} {Cr}_{2} O_{7} (aq)

0.20 M {Cr}^{3 +} (aq)

and

1.0 \times 10^{- 4} {MH}^{+} (aq)

. The half-cell reaction is

{Cr}_{2} {O_{7}}^{2 -} (aq) + 14 H^{+} (aq) + 6 e^{-} \to 2 {Cr}^{3 +} (aq) + 7 H_{2} O (l)

and the standard electrode potential is given as

E^{°} = 1.33 V

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All In One ISC Chemistry Class 12>Chapter 3 - Electrochemistry>Chapter Practice>Q 46

One half cell in a voltaic cell is constructed from a silver wire dipped in silver nitrate solution of unknown concentration. Its other half cell consists of a zinc electrode dipping in $1.0 M$ solution of $Zn ({NO}_{3})_{2}$ . A voltage of $1.48 V$ is measured for this cell. Use this information to calculate the concentration of silver nitrate solution used.
$[E °_{{Zn}^{2 +} / Zn} = - 0.76 V, E °_{{Ag}^{+} / Ag} = + 0.80 V]$

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All In One ISC Chemistry Class 12>Chapter 3 - Electrochemistry>Chapter Practice>Q 47

Degree of dissociation of pure water is

1.9 x 10^{- 9}

. Molar ionic conductances of

H^{+}

ions and

{OH}^{-}

ions at infinite dilution are

200 S {cm}^{2} {mol}^{- 1}

and

350 S {cm}^{2} {mol}^{- 1}

respectively. What is the molar conductance of water?

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All In One ISC Chemistry Class 12>Chapter 3 - Electrochemistry>Chapter Practice>Q 48

The molar conductivity $(π_{m})$ of $KCl$ solutions, at different concentration at $298 K$ , is plotted as shown in the figure given below:

Question Image

Determine the value of ${Λ^{°}}_{m}$ and $A$ for $KCl$ .

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All In One ISC Chemistry Class 12>Chapter 3 - Electrochemistry>Chapter Practice>Q 49

How many molecules of chlorine should be deposited from molten sodium chloride in one minute by a current of

300 mA

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IMPORTANT

All In One ISC Chemistry Class 12>Chapter 3 - Electrochemistry>Chapter Practice>Q 50

Electric current is passed through two cells

A

and

B

in series. Cell

A

contains aqueous solution of

{Ag}_{2} {SO}_{4}

and platinum electrodes. Cell

B

contains aqueous solution of

{CuSO}_{4}

and copper electrodes. The current is passed till

1.6 g

of oxygen is liberated at the anode in cell

A

. Calculate the quantities of copper and silver deposited at the cathode of the two cells. [Atomic mass

O = 16

Cu = 63.5

Ag = 108

]

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IMPORTANT

All In One ISC Chemistry Class 12>Chapter 3 - Electrochemistry>Chapter Practice>Q 51

How many grams of silver could be plated out on a serving tray by electrolysis of a solution containing silver in

+ 1

oxidation state for a period of

8.0 h

at a current of

8.46 A

? What is the area of the tray, if the thickness of the silver plating is

0.00254 cm

? Density of silver is

10.5 g / {cm}^{3}

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IMPORTANT

All In One ISC Chemistry Class 12>Chapter 3 - Electrochemistry>Chapter Practice>Q 52

Calculate the strength of the current required to deposit

1.2 g

of magnesium from molten

{MgCl}_{2}

1 h

[1 F = 96500 C {mol}^{- 1}

, atomic mass of

Mg = 24.0

]

Consider the following cell reaction: 2Fe(s)+O2(g)+4H+(aq) → 2Fe2+(aq)+2H2O(l); E°=1.67 V and [Fe2+]=10-3 M, p(O2) =0.1 atm and pH=3. What is the cell potential at 25°C?

Important Questions on Electrochemistry

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Consider the following cell reaction: $2 Fe (s) + O_{2} (g) + 4 H^{+} (aq) \to 2 {Fe}^{2 +} (aq) + 2 H_{2} O (l); E^{°} = 1.67 V$ and $[{Fe}^{2 +}] = 10^{- 3} M, p (O_{2}) = 0.1 atm$ and $pH = 3$ . What is the cell potential at $25^{°} C$ ?