Electrochemistry Questions

Aluminium oxide may be electrolysed at $1000^{\circ }\text{C}$ to furnish aluminium metal (Atomic mass $=27\text{amu}$; $1\text{Faraday}=96,500\text{Coulombs}$). The cathode reaction is:
$${\text{Al}}^{3+}+3e^{-}\to \text{Al}$$
To prepare $5.12\text{kg}$ of aluminium metal by this method would require:

Calculate ${\Lambda }_{\text{HOAc}}^{\infty }$ using the following molar conductances at infinite dilution at $25^{\circ }\text{C}$:

For a spontaneous reaction the $\Delta G^{\circ }$, equilibrium constant ($K$) and $E_{\text{cell}}^{\circ }$ will be respectively:

Given at $25^{\circ }\text{C}$:$\text{AgI}+e^{-}\to \text{Ag}+{\text{I}}^{-},E^{\circ }=-0.152\text{V}$${\text{Ag}}^{+}+e^{-}\to \text{Ag},E^{\circ }=0.800\text{V}$ What is the value of $\log K_{sp}$ for $\text{AgI}$? ($\frac{2.303RT}{F}=0.059\text{V}$)

The equivalent conductances of two strong electrolytes at infinite dilution in ${\text{H}}_2\text{O}$ at $25^{\circ }\text{C}$ are given:${\Lambda }_{{\text{CH}}_3\text{COONa}}^0=91.0{\text{S cm}}^2\text{/equiv}$${\Lambda }_{\text{HCl}}^0=426.2{\text{S cm}}^2\text{/equiv}$ What additional information is needed to calculate ${\Lambda }^0$ of acetic acid?

The cell, $\text{Zn}|{\text{Zn}}^{2+}(1\text{M})||{\text{Cu}}^{2+}(1\text{M})|\text{Cu}$, $E_{\text{cell}}^0=1.10\text{V}$, was allowed to be completely discharged at $298\text{K}$. The relative concentration of ${\text{Zn}}^{2+}$ to ${\text{Cu}}^{2+}$, $\frac{[{\text{Zn}}^{2+}]}{[{\text{Cu}}^{2+}]}$, is:

Resistance of a conductivity cell filled with a $0.1\text{M}$ solution of an electrolyte is $100\Omega$. The conductivity is $1.29{\text{S m}}^{-1}$. Resistance of the same cell when filled with $0.2\text{M}$ of the same solution is $520\Omega$. The molar conductivity of $0.2\text{M}$ solution of the electrolyte will be:

The molar conductivities ${\Lambda }_{\text{NaOAc}}^{\circ }$ and ${\Lambda }_{\text{HCl}}^{\circ }$ at infinite dilution in water at $25^{\circ }\text{C}$ are $91.0$ and $426.2{\text{S cm}}^2/\text{mol}$ respectively. To calculate ${\Lambda }_{\text{HOAc}}^{\circ }$, the additional value required is:

In a cell that utilizes the reaction $\text{Zn}(s)+2{\text{H}}^{+}(aq)\to {\text{Zn}}^{2+}(aq)+{\text{H}}_2(g)$, the addition of ${\text{H}}_2{\text{SO}}_4$ to the cathode compartment will:

The limiting molar conductivities ${\Lambda }^{\circ }$ for $\text{NaCl},\text{KBr}$ and $\text{KCl}$ are $126,152$ and $150{\text{S cm}}^2{\text{mol}}^{-1}$ respectively. The ${\Lambda }^{\circ }$ for $\text{NaBr}$ is:

The standard e.m.f. of a cell, involving one electron change is found to be $0.591\text{V}$ at $25^{\circ }\text{C}$. The equilibrium constant of the reaction is ($F=96,500{\text{C mol}}^{-1};R=8.314{\text{JK}}^{-1}{\text{mol}}^{-1}$):

Consider the following $E^{\circ }$ values:$E_{{\text{Fe}}^{3+}/{\text{Fe}}^{2+}}^{\circ }=0.77\text{V}$$E_{{\text{Sn}}^{2+}/\text{Sn}}^{\circ }=-0.14\text{V}$ Under standard conditions the potential for the reaction:$\text{Sn}(s)+2{\text{Fe}}^{3+}(aq)\to 2{\text{Fe}}^{2+}(aq)+{\text{Sn}}^{2+}(aq)$ is:

In a hydrogen – oxygen fuel cell, combustion of hydrogen occurs to:

Given $E_{{\text{Cr}}^{3+}/\text{Cr}}^{\circ }=-0.72\text{V}$ and $E_{{\text{Fe}}^{2+}/\text{Fe}}^{\circ }=-0.42\text{V}$. The potential for the cell $\text{Cr}|{\text{Cr}}^{3+}(0.1\text{M})||{\text{Fe}}^{2+}(0.01\text{M})|\text{Fe}$ is:

In a fuel cell methanol is used as fuel and oxygen gas is used as an oxidizer. The reaction is ${\text{CH}}_3\text{OH}(l)+\frac{3}{2}{\text{O}}_2(g)\to {\text{CO}}_2(g)+2{\text{H}}_2\text{O}(l)$. At $298\text{K}$ standard Gibb’s energies of formation for ${\text{CH}}_3\text{OH}(l)$, ${\text{H}}_2\text{O}(l)$ and ${\text{CO}}_2(g)$ are $-166.2$, $-237.2$ and $-394.4{\text{kJ mol}}^{-1}$ respectively. If standard enthalpy of combustion of methanol is $-726{\text{kJ mol}}^{-1}$, efficiency of the fuel cell will be:

Given: $E_{{\text{Fe}}^{3+}/\text{Fe}}^{\circ }=-0.036\text{V}$, $E_{{\text{Fe}}^{2+}/\text{Fe}}^{\circ }=-0.439\text{V}$. The value of standard electrode potential for the change, ${\text{Fe}}^{3+}(aq)+e^{-}\to {\text{Fe}}^{2+}(aq)$ will be:

The Gibbs energy for the decomposition of ${\text{Al}}_2{\text{O}}_3$ at $500^{\circ }\text{C}$ is as follows:$\frac{2}{3}{\text{Al}}_2{\text{O}}_3\to \frac{4}{3}\text{Al}+{\text{O}}_2,{\Delta }_{r}G=+966{\text{kJ mol}}^{-1}$ The potential difference needed for electrolytic reduction of ${\text{Al}}_2{\text{O}}_3$ at $500^{\circ }\text{C}$ is at least:

The reduction potential of hydrogen half cell will be negative if:

The standard reduction potentials for ${\text{Zn}}^{2+}/\text{Zn}$, ${\text{Ni}}^{2+}/\text{Ni}$, and ${\text{Fe}}^{2+}/\text{Fe}$ are $-0.76$, $-0.23$ and $-0.44\text{V}$ respectively. The reaction $\text{X}+{\text{Y}}^{2+}\to {\text{X}}^{2+}+\text{Y}$ will be spontaneous when: