Electrochemistry Questions

If the molar conductivity (${\Lambda }_m$) of a $0.050{\text{mol L}}^{-1}$ solution of a monobasic weak acid is $90{\text{S cm}}^2{\text{ mol}}^{-1}$, its extent (degree) of dissociation will be[Assume ${\lambda }_{+}^{\circ }=349.6{\text{S cm}}^2{\text{ mol}}^{-1}$ and ${\lambda }_{-}^{\circ }=50.4{\text{S cm}}^2{\text{ mol}}^{-1}$ ]

Standard electrode potential of three metals $X,Y$ and $Z$ are $-1.2\text{V},+0.5\text{V}$ and $-3.0\text{V}$ respectively. The reducing power of these metals will be:

Standard electrode potential for ${\text{Sn}}^{4+}/{\text{Sn}}^{2+}$ couple is $+0.15\text{V}$ and that for the ${\text{Cr}}^{3+}/\text{Cr}$ couple is $-0.74\text{V}$. These two couples in their standard state are connected to make a cell. The cell potential will be:

The electrode potentials for ${\text{Cu}}_{(\text{aq})}^{2+}+e^{-}\to {\text{Cu}}_{(\text{aq})}^{+}$ and ${\text{Cu}}_{(\text{aq})}^{+}+e^{-}\to {\text{Cu}}_{(\text{s})}$ are $+0.15\text{V}$ and $+0.50\text{V}$ respectively. The value of $E_{{\text{Cu}}^{2+}/\text{Cu}}^{\circ }$ will be:

Standard reduction potentials of the half reactions are given below:${\text{F}}_{2(\text{g})}+2e^{-}\to 2{\text{F}}_{(\text{aq})}^{-};E^{\circ }=+2.85\text{V}$${\text{Cl}}_{2(\text{g})}+2e^{-}\to 2{\text{Cl}}_{(\text{aq})}^{-};E^{\circ }=+1.36\text{V}$${\text{Br}}_{2(\text{g})}+2e^{-}\to 2{\text{Br}}_{(\text{aq})}^{-};E^{\circ }=+1.06\text{V}$${\text{I}}_{2(\text{g})}+2e^{-}\to 2{\text{I}}_{(\text{aq})}^{-};E^{\circ }=+0.53\text{V}$ The strongest oxidising and reducing agents respectively are:

Zinc can be coated on iron to produce galvanized iron but the reverse is not possible. It is because:

Limiting molar conductivity of ${\text{NH}}_4\text{OH}$ (i.e., ${\Lambda }_m^{\circ }({\text{NH}}_4\text{OH})$) is equal to:

A hydrogen gas electrode is made by dipping platinum wire in a solution of HCl of $pH=10$. The oxidation potential of the electrode would be:

At $25^{\circ }\text{C}$, the molar conductance of a $0.1\text{M}$ aqueous solution of ammonium hydroxide is $9.54{\Omega }^{-1}{\text{cm}}^2{\text{mol}}^{-1}$ and at infinite dilution its molar conductance is $238{\Omega }^{-1}{\text{cm}}^2{\text{mol}}^{-1}$. The degree of ionisation of ammonium hydroxide at the same concentration and temperature is:

A button cell used in watches functions as follows:$\text{Zn}(s)+{\text{Ag}}_2\text{O}(s)+{\text{H}}_2\text{O}(l)\to 2\text{Ag}(s)+{\text{Zn}}^{2+}(aq)+2{\text{OH}}^{-}(aq)$ Given:$E_{{\text{Zn}}^{2+}/\text{Zn}}^{\circ }=-0.76\text{V}$$E_{{\text{Ag}}_2\text{O}/\text{Ag}}^{\circ }=0.34\text{V}$ The cell potential $E_{cell}^{\circ }$ is:

When $0.1\text{mol}$ ${\text{MnO}}_4^{2-}$ is oxidized, the quantity of electricity required to completely oxidize ${\text{MnO}}_4^{2-}$ to ${\text{MnO}}_4^{-}$ is:

The weight of silver (at. wt. $=108$) displaced by a quantity of electricity which displaces $5600\text{mL}$ of ${\text{O}}_2$ at STP will be:

Aqueous solution of which of the following compounds is the best conductor of electric current?

The pressure of ${\text{H}}_2$ required to make the potential of ${\text{H}}_2$ – electrode zero in pure water at $298\text{K}$ is:

The molar conductivity of a $0.5{\text{mol/dm}}^3$ solution of ${\text{AgNO}}_3$ with electrolytic conductivity of $5.76\times 10^{-3}{\text{S cm}}^{-1}$ at $298\text{K}$ is:

During the electrolysis of molten sodium chloride, the time required to produce $0.10\text{mol}$ of chlorine gas using a current of $3\text{amperes}$ is:

If the $E_{\text{cell}}^{\circ }$ for a given reaction has a negative value, which of the following gives the correct relationships for the values of $\Delta G^{\circ }$ and $K_{\text{eq}}$?

The number of electrons delivered at the cathode during electrolysis by a current of $1\text{ampere}$ in $60\text{seconds}$ is (charge on electron $=1.60\times 10^{-19}\text{C}$):

Molar conductivities (${\Lambda }_m^{\circ }$) at infinite dilution of $\text{NaCl}$, $\text{HCl}$ and ${\text{CH}}_3\text{COONa}$ are $126.4$, $425.9$ and $91.0{\text{S cm}}^2{\text{mol}}^{-1}$ respectively. ${\Lambda }_m^{\circ }$ for ${\text{CH}}_3\text{COOH}$ will be:

The Gibbs energy for the decomposition of ${\text{Al}}_2{\text{O}}_3$ at $500^{\circ }\text{C}$ is as follows:
$$\frac{2}{3}{\text{Al}}_2{\text{O}}_3\to \frac{4}{3}\text{Al}+{\text{O}}_2;{\Delta }_{r}G=+960{\text{kJ mol}}^{-1}$$
The potential difference needed for the electrolytic reduction of aluminium oxide (${\text{Al}}_2{\text{O}}_3$) at $500^{\circ }\text{C}$ is at least:

A solution contains ${\text{Fe}}^{2+}$, ${\text{Fe}}^{3+}$ and ${\text{I}}^{-}$ ions. It was treated with iodine at $35^{\circ }\text{C}$. $E^{\circ }$ for ${\text{Fe}}^{3+}/{\text{Fe}}^{2+}=+0.77\text{V}$ and $E^{\circ }$ for ${\text{I}}_2/2{\text{I}}^{-}=0.536\text{V}$. The favourable redox reaction is:

For the reduction of silver ions with copper metal, the standard cell potential was found to be $+0.46\text{V}$ at $25^{\circ }\text{C}$. The value of standard Gibbs energy, $\Delta G^{\circ }$ will be ($F=96500{\text{C mol}}^{-1}$):

An increase in equivalent conductance of a strong electrolyte with dilution is mainly due to:

The equivalent conductance of $M/32$ solution of a weak monobasic acid is $8.0{\text{mhos cm}}^2$ and at infinite dilution is $400{\text{mhos cm}}^2$. The dissociation constant of this acid is:

${\text{Al}}_2{\text{O}}_3$ is reduced by electrolysis. If $4.0\times 10^4\text{amperes}$ of current is passed through molten ${\text{Al}}_2{\text{O}}_3$ for $6\text{hours}$, what mass of aluminium is produced? (At. mass of $\text{Al}=27{\text{g mol}}^{-1}$)

Given:(i) ${\text{Cu}}^{2+}+2e^{-}\to \text{Cu}$, $E^{\circ }=0.337\text{V}$ (ii) ${\text{Cu}}^{2+}+e^{-}\to {\text{Cu}}^{+}$, $E^{\circ }=0.153\text{V}$ Electrode potential, $E^{\circ }$ for the reaction, ${\text{Cu}}^{+}+e^{-}\to \text{Cu}$, will be:

On the basis of the standard reduction potential values, the strongest oxidizing agent is (assuming common values for Iron complexes):

Standard free energies of formation at $298\text{K}$ are $-237.2,-394.4$ and $-8.2$ for ${\text{H}}_2\text{O}(l),{\text{CO}}_2(g)$ and pentane $(g)$ respectively. The value of $E_{\text{cell}}^{\circ }$ for the pentane-oxygen fuel cell is:

Kohlrausch's law states that at:

A hypothetical electrochemical cell is shown below $\text{A}|{\text{A}}^{+}(x\text{M})||{\text{B}}^{+}(y\text{M})|\text{B}$.The emf measured is $+0.20\text{V}$. The cell reaction is :

If $E_{{\text{Fe}}^{2+}/\text{Fe}}^{\circ }=-0.441\text{V}$ and $E_{{\text{Fe}}^{3+}/{\text{Fe}}^{2+}}^{\circ }=0.771\text{V}$, the standard emf of the reaction :$\text{Fe}+2{\text{Fe}}^{3+}\to 3{\text{Fe}}^{2+}$ will be :

Assertion : Galvanised iron does not rust.Reason : Zinc has a more negative electrode potential than iron.

The chemical reaction, $2{\text{AgCl}}_{(s)}+{\text{H}}_{2(g)}\to 2{\text{HCl}}_{(aq)}+2{\text{Ag}}_{(s)}$ taking place in a galvanic cell is represented by the notation: