Electrode Potential

Q.

When do we use the formula delta G=-nFE. and when do we use E=E⁰-0.059/nlogKc?

Are there any specific conditions for using these two?

Q.

In the button cell widely used in watches and other devices the following reaction takes place :

$Zn\left(s\right)+A{g}_{2}O\left(s\right)+H_{2}O\left(l\right)\to Z{n}^{2+}\left(aq\right)+2Ag\left(s\right)+2O{H}^{-}\left(aq\right)Determine{\Delta }_r{G}^{\circ }and{E}^{\circ }forthereaction.[Given,E_{\frac{Zn}{Z{n}^{2+}}}^{\circ }=-0.76Vand{E}_{\frac{A{g}^{+}}{Ag}}^{\circ }+0.34V]$

Q.

4.5 g of aluminium is deposited at cathode from Al³⁺ solution by a certain quantity of electric charge. The volume of hydrogen produced at STP from H⁺ ions is solution by the same quantity of electric charge will be?

Q. Four alkali metals $A,B,C\text{and}D$ are having respective standard electrode potential as $-3.05,-1.66,-0.40$ and $0.80V$.
Which one will be the powerful reducing agent?

1. A
2. B
3. C
4. D

Q. Elaborative difference between EMF\:and electrode potential.

Q. Consider the following relations for emf of an electrochemical cell:
(i) EMF of cell = (Oxidation potential of anode) - (Reduction potential of cathode )
(ii) EMF of cell = (Oxidation potential of anode) + (Reduction potential of cathode )
(iii) EMF of cell = (Reduction potential of anode ) + (Reduction potential of cathode )
(iv) EMF of cell = (Oxidation potential of anode) - (Oxidation potential of cathode)

Which of the above relations are correct?

1. (iii) and (i)
2. (i) and (ii)
3. (iii) and (i)
4. (ii) and (iv)

Q.

Given below are the half-cell reaction:
$M{n}^{2+}+2e^{\ominus }\to Mn;E^{\ominus }=-1.18V$
$2(M{n}^{3+}+e^{\ominus }\to M{n}^{2+};E^{\ominus }=+1.51V$

The $E^{\ominus }$ for $3M{n}^{2+}\to Mn+2M{n}^{3+}$ will be:
(IIT-JEE 2014)

1. (a) -0.33 V; the reaction will not occur

2. (b) -0.33 V; the reaction will occur

3. (c) -2.69 V; the reaction will not occur

4. (d) -2.69 V; the reaction will occur

Q. The standard oxidation potentials, $E^o$, for the half cell reactions are as follows:
$Zn\to Z{n}^{2+}+2e^{-},E^o=0.76VFe\to F{e}^{2+}+2e^{-},E^o=0.41V$
The EMF for the cell oxidation,
$F{e}^{2+}+Zn\to Z{n}^{2+}+Fe$(Give your answer upto two decimal only)

Q. When a standard reduction potential of the metal is more negative, its ability to displace hydrogen from acid will

1. increase
2. decrease
3. remain unchanged
4. depends on the acid

Q.

Extraction of gold and silver involves leaching the metal with $C{N}^{-}$ ion. The metal is recovered by ________________.

1. calcination followed by roasting.

2. thermal decomposition of metal complex.

3. displacement of metal by some other metal from the complex ion.

4. roasting of metal complex.

Q. Which of the following option(s) is/are true regarding electrochemical series ?

1. Negative value of $E^{\circ }$ signifies that the redox couple is a stronger oxidising agent than the $H^{+}/H_2$ couple
2. Negative value of $E^{\circ }$ signifies that the redox couple is a stronger reducing agent than the $H^{+}/H_2$ couple
3. Polarity of the electrode system and the electrode reaction can be easily predicted.
4. Spontaneity and feasibility of the cell can be easily predicted

Q.

Which of the following does not corrode when exposed to the atmosphere?

1. Iron

2. Copper

3. Gold

4. Silver

Q. By how much would the oxidising power of the $\left(Mn{O}_4^{-}|M{n}^{2+}\right)$ couple change if the $H^{+}$ ions concentration is decreased $100$ times at ${25}^{\circ }C$?

1. Increases by $189mV$
2. Decreases by $189mV$
3. Increases by $19mV$
4. Decreases by $19mV$

Q.

FPGAs are power efficient when compared to GPU

Q. The cell representation of electrochemical cell using the cell reaction:
$Ni\left(s\right)+2F{e}^{3+}\to N{i}^{2+}+2F{e}^{2+}isNi\left(s\right)|N{i}^{2+}\left(aq\right)||F{e}^{3+}\left(aq\right),F{e}^{2+}\left(aq\right)$

1. True
2. False

Q. At what concentration of $C{u}^{2+}$ in a solution of $CuS{O}_4$ will the electrode potential be zero at ${25}^{\circ }\text{C}$? Given: $E_{cu|c{u}^{2+}}^o=-0.34\text{V}$

1. $3.01\times {10}^{-12}$
2. $2.98\times {10}^{-15}$
3. $3.98\times {10}^{-20}$
4. $2.89\times {10}^{-18}$

Q.

Given the standard electrode potentials,

$\frac{K^{+}}{K}=-2.93V,$

$\frac{A{g}^{+}}{Ag}=0.80V$

$\frac{H{g}^{2+}}{Hg}=0.79V,$

$\frac{M{g}^{2+}}{Mg}=-2.37V$

$\frac{C{r}^{3+}}{Cr}=-0.74V$

Arrange these metals in their increasing order of reducing power.

Q. 46. If standard reduction potential of cu2+/cu and cu2+/cu+1 is x and y respectively then standard electrode potential of cu+/cu becomes

Q.

The standard reduction electrode potentials of four elements are

A=-0.250 V B=-0.136 V

C=-0.126 D=-0.402 V

The element that displaces A from its compounds is

1. B

2. C

3. D

4. None of these

Q.

Arrange Ag, Cr, and Hg metals in the increasing order of reducing power.

Given:

$$\begin{gathered} {{\mathrm{E}}^0}_{{\mathrm{Ag}}^{+}/\mathrm{Ag}}=+0.80\mathrm{V} \\ {{\mathrm{E}}^0}_{{\mathrm{Cr}}^{3+}/\mathrm{Cr}}=-0.74\mathrm{V} \\ {{\mathrm{E}}^0}_{{\mathrm{Hg}}^{2+}/\mathrm{Hg}}=+0.79\mathrm{V} \end{gathered}$$

1. $\mathrm{Cr}>\mathrm{Hg}>\mathrm{Ag}$

2. $\mathrm{Hg}>\mathrm{Ag}>\mathrm{Cr}$

3. $\mathrm{Ag}>\mathrm{Cr}>\mathrm{Hg}$

4. $\mathrm{Ag}>\mathrm{Hg}>\mathrm{Cr}$

Q. WHY RATE CONSTANT(K) IS INDEPENDENT OF INITIAL CONCENTRATION OF REACTENT?

Q. Given below are the half - cell reactions
$M{n}^{2+}+2e^{-}\to Mn;E^{\circ }=-1.18eV$
$2(M{n}^{3+}+e^{-}\to M{n}^{2+});E^0=+1.51eV$
The $E^{\circ }$for $3M{n}^{2+}\to Mn+2M{n}^{3+}$ will be

1. -0.33 V; the reaction will not occur
2. -0.33 V; the reaction will occur
3. -2.69 V; the reaction will not occur
4. -2.69 V; the reaction will occur

Q. A galvanic cell is constructed by coupling of an iron and a nickel electrode. If at $298K$
$E_{N{i}^{2+}\left(aq\right)/Ni\left(s\right)}^{\circ }=-0.24V$
$E_{F{e}^{2+}\left(aq\right)/Fe\left(s\right)}^{\circ }=-0.44V$
then calculate the EMF of the cell

1. $+0.68V$
2. $-0.68V$
3. $+0.2V$
4. $-0.2V$

Q. zn + fe2+ gives zn2+ + fe. the value of kc for this reaction is 10^23 calculate the standard free energy change

Q.

On what factor does the amount of product formed at an electrode depend?

Q. Which of the following is true regarding the electrode potential?

1. It is the potential difference developed between the two ends of a salt bridge in a solution.
2. It is the potential difference developed between an electrode and an electrolyte in a solution.
3. It is the potential difference developed between electrolyte and salt bridge in a solution.
4. None of the above

Q. Why is cathode in an electrolytic cell considered to be negative and anode positive?

Q.

The tendency of a chemical species to acquire electrons from an electrode is measured by:

1. Oxidation potential

2. Reduction potential

3. Cell potential
4. None of these

Q.

Define electrochemical cell.

Q. 32. Ksp of AGI is 16. Standard reduction electrode potential of Ag is 0.8V. Find the the EMF for half cell reaction.