Redox Reactions and Electrochemistry — JEE Main PYQs

Consider the following two half-cell reactions along with the standard reduction potential given :

$$\mathrm{CO_2 + 6H^+ + 6e^- \longrightarrow CH_3OH + H_2O} \qquad E^{o}_{red} = 0.02\ \mathrm{V}$$

$$\mathrm{\tfrac{1}{2}O_2 + 2H^+ + 2e^- \longrightarrow H_2O} \qquad E^{o}_{red} = 1.23\ \mathrm{V}$$

A fuel cell was set up using the above two reactions such that the cell operates under the standard condition of 1 bar pressure and 298 K temperature. The fuel cell works with 80% efficiency. If the work derived from the cell using 1 mol of $\mathrm{CH_3OH}$ is used to compress an ideal gas isothermally against a constant pressure of 1 kPa, then the change in the volume of the gas, $\Delta V =$ __________ m$^3$. (nearest integer)

Given : $F = 96500$ C mol$^{-1}$

In order to oxidise a mixture of 1 mole each of $\mathrm{FeC_2O_4}$, $\mathrm{Fe_2(C_2O_4)_3}$, $\mathrm{FeSO_4}$ and $\mathrm{Fe_2(SO_4)_3}$ in acidic medium, the number of moles of $\mathrm{KMnO_4}$ required is

An electrochemical cell, consist of the following two redox couples, $\mathrm{M^{x+}(aq)/M(s)}$ $[E^{\ominus}_{red} = +0.15\ \mathrm{V}]$ and $\mathrm{Fe^{3+}(aq)/Fe(s)}$ $[E^{\ominus}_{red} = -0.036\ \mathrm{V}]$. The cell EMF ($E_{cell}$) is recorded to be 0.2057 V. If the reaction quotient of the electrochemical reaction is found to be $10^{-2}$, then the value of $x$ is ____________. (Nearest integer)

[Given : M is a p-block metal and $\dfrac{2.303RT}{F} = 0.059\ \mathrm{V}$]

One half cell in a voltaic cell is constructed by dipping silver rod in $\mathrm{AgNO_3}$ solution of unknown concentration, other half cell is Zn rod dipped in 1 molar solution of $\mathrm{ZnSO_4}$.

A voltage of 1.60 V is measured at 298 K for this cell. What is the concentration of $\mathrm{Ag^+}$ ions used in terms of $\log x$ ($x = \mathrm{[Ag^+]}$)?

$E^{\ominus}_{\mathrm{Zn^{2+}/Zn}} = -0.76\ \mathrm{V}, \quad E^{\ominus}_{\mathrm{Ag^+/Ag}} = +0.80\ \mathrm{V}, \quad \dfrac{2.303RT}{F} = 0.059\ \mathrm{V}$

At 298 K, the molar conductivity of $x\%$ (w/w) MX solution (aqueous) is $123.5\ \mathrm{S\ cm^2\ mol^{-1}}$. The conductance of same solution is $1.9 \times 10^{-3}\ \mathrm{S}$. The value of $x$ is ________ $\times 10^{-2}$.

(Given : cell constant $= 1.3\ \mathrm{cm^{-1}}$; molar mass of MX is 75 $\mathrm{g\ mol^{-1}}$, density of aqueous solution of MX at 298 K is $1.0\ \mathrm{g\ mL^{-1}}$)

Consider the following data.

Electrolyte	$\Lambda^{\circ}_{m}$ (S cm$^2$ mol$^{-1}$)
$\mathrm{BaCl_2}$	$x_1$
$\mathrm{H_2SO_4}$	$x_2$
$\mathrm{HCl}$	$x_3$

$\mathrm{BaSO_4}$ is sparingly soluble in water. If the conductivity of the saturated $\mathrm{BaSO_4}$ solution is $x$ S cm$^{-1}$ then the solubility product of $\mathrm{BaSO_4}$ can be given as

(Here $\Lambda_m = \Lambda^{\circ}_{m}$)

For a general redox reaction

Anode : $\mathrm{Red_1 \rightarrow Ox_1^{n_1^{+}} + n_1 e^{-}}$

Cathode : $\mathrm{Ox_2 + n_2 e^{-} \rightarrow Red_2^{n_2^{-}}}$

Which of the following statement is incorrect?

500 mL of 0.2 M $\mathrm{MnO_4^{-}}$ solution in basic medium when mixed with 500 mL of 1.5 M KI solution, oxidises iodide ions to liberate molecular iodine. This liberated iodine is then titrated with a standard $x$ M thiosulphate solution in presence of starch till the end point. If 300 mL of thiosulphate was consumed, then the value of $x$ is ________.

Given at 298 K :

$\mathrm{E^{\ominus}_{Fe^{2+}/Fe}} = \mathrm{X}$ Volt

$\mathrm{E^{\ominus}_{Fe^{3+}/Fe}} = \mathrm{Y}$ Volt

The $\mathrm{E^{\ominus}_{Fe^{3+}/Fe^{2+}}}$ in Volt at 298 K is given by :

Consider the following electrochemical cell at standard condition.

$$\mathrm{Au(s)\,|\,QH_2, Q\,|\,NH_4X(0.01\ M)\,||\,Ag^+(1\ M)\,|\,Ag(s)} \quad E_{cell} = +0.4\ \mathrm{V}$$

The couple $\mathrm{QH_2/Q}$ represents quinhydrone electrode, the half cell reaction is given below :

[Figure: p-benzoquinone (Q) $+ 2e^- + 2H^+ \rightarrow$ hydroquinone (QH$_2$)] $\quad E^{\circ}_{Q/QH_2} = +0.7\ \mathrm{V}$

$$\left[\text{Given} : E^{\circ}_{Ag^+/Ag} = +0.8\ \mathrm{V} \text{ and } \frac{2.303RT}{F} = 0.06\ \mathrm{V}\right]$$

The $pK_b$ value of the ammonium halide salt ($\mathrm{NH_4X}$) used here is __________. (nearest integer)

0.2% (w/v) solution of NaOH is measured to have resistivity 870.0 $\mathrm{m\Omega\ m}$. The molar conductivity of the solution will be __________ $\times 10^{2}\ \mathrm{mS\ dm^{2}\ mol^{-1}}$. (Nearest integer)

Correct order of limiting molar conductivity for cations in water at 298 K is :

40 mL of a mixture of $\mathrm{CH_3COOH}$ and HCl (aqueous solution) is titrated against 0.1 M NaOH solution conductometrically. Which of the following statement is correct?

[Figure: conductometric titration curve — Conductance (mS) vs $V_{\mathrm{NaOH}}$/mL; conductance falls from A to a minimum at B (2.0 mL), rises gently from B to C (5.0 mL), then rises steeply from C to D]

The standard cell potential $\left(\mathrm{E^{\ominus}_{cell}}\right)$ of a fuel cell based on the oxidation of methanol in air that has been used to power television relay station is measured as 1.21 V. The standard half cell reduction potential for $\mathrm{O_2}$ $\left(\mathrm{E^{\circ}_{O_2/H_2O}}\right)$ is 1.229 V.

Choose the correct statement:

The molar conductance of an infinitely dilute solution of ammonium chloride was found to be $185\ \mathrm{S\ cm^2\ mol^{-1}}$ and the ionic conductance of hydroxyl and chloride ions are 170 and $70\ \mathrm{S\ cm^2\ mol^{-1}}$, respectively. If molar conductance of 0.02 M solution of ammonium hydroxide is $85.5\ \mathrm{S\ cm^2\ mol^{-1}}$, its degree of dissociation is given by $x \times 10^{-1}$.

The value of $x$ is _________. (Nearest integer)

Given below are two statements:

Statement I: Mohr's salt is composed of only three types of ions-ferrous, ammonium and sulfate.

Statement II: If the molar conductance at infinite dilution for ferrous, ammonium and sulfate ions are $x_1$, $x_2$ and $x_3$ S cm$^2$ mol$^{-1}$, respectively then the molar conductance for Mohr's salt solution at infinite dilution would be given by $x_1 + x_2 + 2x_3$

In the light of the given statements, choose the correct answer from the options given below:

1 Faraday electricity was passed through $\mathrm{Cu^{2+}}$ (1.5 M, 1 L) /Cu and 0.1 Faraday was passed through $\mathrm{Ag^{+}}$ (0.2 M, 1 L)/Ag electrolytic cells. After this the two cells were connected as shown below to make an electrochemical cell. The emf of the cell thus formed at 298 K is __________ mV (nearest integer)

[Figure: electrochemical cell — Cu electrode in $\mathrm{Cu^{2+}(aq)}$ and Ag electrode in $\mathrm{Ag^{+}(aq)}$ connected through a salt bridge and a voltmeter]

Given : $E^{\circ}_{\mathrm{Cu^{2+}/Cu}} = 0.34$ V

$E^{\circ}_{\mathrm{Ag^{+}/Ag}} = 0.8$ V

$\frac{2.303RT}{F} = 0.06$ V

Given below are two statements :

1 M aqueous solutions of each of $\mathrm{Cu(NO_3)_2}$, $\mathrm{AgNO_3}$, $\mathrm{Hg_2(NO_3)_2}$, $\mathrm{Mg(NO_3)_2}$ are electrolysed using inert electrodes. Given : $\mathrm{E^{\theta}_{Ag^+/Ag}} = 0.80\ \mathrm{V}$, $\mathrm{E^{\theta}_{Hg_2^{2+}/Hg}} = 0.79\ \mathrm{V}$, $\mathrm{E^{\theta}_{Cu^{2+}/Cu}} = 0.24\ \mathrm{V}$ and $\mathrm{E^{\theta}_{Mg^{2+}/Mg}} = -2.37\ \mathrm{V}$.

Statement (I) : With increasing voltage, the sequence of deposition of metals on the cathode will be Ag, Hg and Cu.

Statement (II) : Magnesium will not be deposited at cathode instead oxygen gas will be evolved at the cathode.

In the light of the above statements, choose the most appropriate answer from the options given below :

Consider the following half cell reaction

$$\mathrm{Cr_2O_7^{2-}(aq) + 6e^- + 14H^+(aq) \longrightarrow 2Cr^{3+}(aq) + 7H_2O(l)}$$

The reaction was conducted with the ratio of $\frac{[\mathrm{Cr^{3+}}]^2}{[\mathrm{Cr_2O_7^{2-}}]} = 10^{-6}$. The pH value at which the EMF of the half cell will become zero is __________. (nearest integer value)

[Given : standard half cell reduction potential $E^{\circ}_{\mathrm{Cr_2O_7^{2-},\ H^+/Cr^{3+}}} = 1.33\ \mathrm{V}$, $\frac{2.303RT}{F} = 0.059\ \mathrm{V}$]

A solution of aluminium chloride is electrolysed for 30 minutes using a current of 2A. The amount of the aluminium deposited at the cathode is ________.

[Given : molar mass of aluminium and chlorine are $27\ \mathrm{g\ mol^{-1}}$ and $35.5\ \mathrm{g\ mol^{-1}}$ respectively. Faraday constant $= 96500\ \mathrm{C\ mol^{-1}}$]

Which of the following electrolyte can be used to obtain $\mathrm{H_2S_2O_8}$ by the process of electrolysis ?

The species which does not undergo disproportionation reaction is :

$$\mathrm{FeO_4^{2-}} \xrightarrow{+2.0\ \mathrm{V}} \mathrm{Fe^{3+}} \xrightarrow{0.8\ \mathrm{V}} \mathrm{Fe^{2+}} \xrightarrow{-0.5\ \mathrm{V}} \mathrm{Fe^{0}}$$

In the above diagram, the standard electrode potentials are given in volts (over the arrow). The value of $E^{\ominus}_{\mathrm{FeO_4^{2-}}/\mathrm{Fe^{2+}}}$ is

Standard electrode potentials for a few half cells are mentioned below :

$$E^{\circ}_{Cu^{2+}/Cu} = 0.34\ \mathrm{V},\quad E^{\circ}_{Zn^{2+}/Zn} = -0.76\ \mathrm{V}$$

$$E^{\circ}_{Ag^{+}/Ag} = 0.80\ \mathrm{V},\quad E^{\circ}_{Mg^{2+}/Mg} = -2.37\ \mathrm{V}$$

Which one of the following cells gives the most negative value of $\Delta G^{\circ}$ ?

For the given cell $$\mathrm{Fe^{2+}_{(aq)} + Ag^{+}_{(aq)} \to Fe^{3+}_{(aq)} + Ag_{(s)}}$$ The standard cell potential of the above reaction is Given: $\mathrm{Ag^+ + e^- \to Ag} \quad E^{\ominus} = x\ \mathrm{V}$

$\mathrm{Fe^{2+} + 2e^- \to Fe} \quad E^{\ominus} = y\ \mathrm{V}$

$\mathrm{Fe^{3+} + 3e^- \to Fe} \quad E^{\ominus} = z\ \mathrm{V}$

Based on the data given below :

$$\mathrm{E^\circ_{Cr_2O_7^{2-}/Cr^{3+}}} = 1.33\ \mathrm{V} \qquad \mathrm{E^\circ_{Cl_2/Cl^-}} = 1.36\ \mathrm{V}$$

$$\mathrm{E^\circ_{MnO_4^-/Mn^{2+}}} = 1.51\ \mathrm{V} \qquad \mathrm{E^\circ_{Cr^{3+}/Cr}} = -0.74\ \mathrm{V}$$

the strongest reducing agent is :

Match the LIST-I with LIST-II

	LIST-I (Redox Reaction)		LIST-II (Type of Redox Reaction)
A.	$\mathrm{CH_{4(g)} + 2O_{2(g)} \xrightarrow{\Delta} CO_{2(g)} + 2H_2O_{(l)}}$	I.	Disproportionation reaction
B.	$\mathrm{2NaH_{(s)} \xrightarrow{\Delta} 2Na_{(s)} + H_{2(g)}}$	II.	Combination reaction
C.	$\mathrm{V_2O_{5(s)} + 5Ca_{(s)} \xrightarrow{\Delta} 2V_{(s)} + 5CaO_{(s)}}$	III.	Decomposition reaction
D.	$\mathrm{2H_2O_{2(aq)} \xrightarrow{\Delta} 2H_2O_{(l)} + O_{2(g)}}$	IV.	Displacement reaction

Choose the correct answer from the options given below:

Given below is the plot of the molar conductivity vs $\sqrt{\text{concentration}}$ for KCl in aqueous solution.

[Figure: graph of molar conductivity $\Lambda_m\ (\mathrm{S\ cm^2\ mol^{-1}})$ vs $\sqrt{C}\ (\mathrm{mol/L})^{1/2}$ — a straight line with negative slope passing through $\Lambda_m = 150$ at $\sqrt{C} = 0.1$ and $\Lambda_m = 100$ at $\sqrt{C} = 0.15$]

If, for the higher concentration of KCl solution, the resistance of the conductivity cell is 100 $\Omega$, then the resistance of the same cell with the dilute solution is 'x' $\Omega$.

The value of x is ______ (Nearest integer)

Electrolysis of 600 mL aqueous solution of NaCl for 5 min changes the pH of the solution to 12. The current in Amperes used for the given electrolysis is __________. (Nearest integer).

One of the commonly used electrode is calomel electrode. Under which of the following categories, calomel electrode comes ?

What pressure (bar) of $\mathrm{H_2}$ would be required to make emf of hydrogen electrode zero in pure water at 25°C ?

Only 2 mL of $\mathrm{KMnO_4}$ solution of unknown molarity is required to reach the end point of a titration of 20 mL of oxalic acid (2 M) in acidic medium. The molarity of $\mathrm{KMnO_4}$ solution should be ________ M.

Fuel cell, using hydrogen and oxygen as fuels,

A. has been used in spaceship B. has as efficiency of 40% to produce electricity C. uses aluminum as catalysts D. is eco-friendry E. is actually a type of Galvanic cell only

Choose the correct answer from the options given below:

For a strong electrolyte, a plot of molar conductivity against $(\text{concentration})^{1/2}$ is a straight line, with a negative slope, the correct unit for the slope is

The reaction at cathode in the cells commonly used in clocks involves.

Molar ionic conductivities of divalent cation and anion are $57~\mathrm{S~cm^2~mol^{-1}}$ and $73~\mathrm{S~cm^2~mol^{-1}}$ respectively. The molar conductivity of solution of an electrolyte with the above cation and anion will be :

For the electro chemical cell

$$\mathrm{M | M^{2+} \| X | X^{2-}}$$

If $\mathrm{E^0_{(M^{2+}/M)}} = 0.46 \mathrm{~V}$ and $\mathrm{E^0_{(X/X^{2-})}} = 0.34 \mathrm{~V}$.

Which of the following is correct ?

The quantity of silver deposited when one coulomb charge is passed through $\mathrm{AgNO_3}$ solution :

A conductivity cell with two electrodes (dark side) are half filled with infinitely dilute aqueous solution of a weak electrolyte. If volume is doubled by adding more water at constant temperature, the molar conductivity of the cell will -

[Figure: a cubic conductivity cell of dimensions 1 cm × 1 cm × 1 cm with two shaded (dark) electrode plates on opposite faces, marked (+) and (−)]

Match List - I with List - II.

List - I (Reaction)	List - II (Type of redox reaction)
(A) $\mathrm{N_{2(g)} + O_{2(g)} \to 2NO_{(g)}}$	(I) Decomposition
(B) $\mathrm{2Pb(NO_3)_{2(s)} \to 2PbO_{(s)} + 4NO_{2(g)} + O_{2(g)}}$	(II) Displacement
(C) $\mathrm{2Na_{(s)} + 2H_2O_{(l)} \to 2NaOH_{(aq.)} + H_{2(g)}}$	(III) Disproportionation
(D) $\mathrm{2NO_{2(g)} + 2\,{}^-OH_{(aq.)} \to NO^-_{2(aq.)} + NO^-_{3(aq.)} + H_2O_{(l)}}$	(IV) Combination

Choose the correct answer from the options given below :

How can an electrochemical cell be converted into an electrolytic cell ?

Thiosulphate reacts differently with iodine and bromine in the reactions given below:

$$\mathrm{2S_2O_3^{2-} + I_2 \rightarrow S_4O_6^{2-} + 2I^-}$$

$$\mathrm{S_2O_3^{2-} + 5Br_2 + 5H_2O \rightarrow 2SO_4^{2-} + 4Br^- + 10H^+}$$

Which of the following statement justifies the above dual behaviour of thiosulphate?

Iron (III) catalyses the reaction between iodide and persulphate ions, in which

A. $\mathrm{Fe^{3+}}$ oxidises the iodide ion

B. $\mathrm{Fe^{3+}}$ oxidises the persulphate ion

C. $\mathrm{Fe^{2+}}$ reduces the iodide ion

D. $\mathrm{Fe^{2+}}$ reduces the persulphate ion

Choose the most appropriate answer from the options given below:

The emf of cell $\mathrm{Tl}\left|\underset{(0.001\,\mathrm{M})}{\mathrm{Tl}^{+}}\right\|\left.\underset{(0.01\,\mathrm{M})}{\mathrm{Cu}^{2+}}\right|\mathrm{Cu}$ is 0.83 V at 298 K. It could be increased by :

The reaction ;

$$\frac{1}{2}\mathrm{H_{2(g)}} + \mathrm{AgCl_{(s)}} \rightarrow \mathrm{H^+_{(aq)}} + \mathrm{Cl^-_{(aq)}} + \mathrm{Ag_{(s)}}$$

occurs in which of the following galvanic cell :

The molar conductivity for electrolytes A and B are plotted against $\mathrm{C^{1/2}}$ as shown below. Electrolytes A and B respectively are :

[Figure: plot of $\Lambda_m\ (\mathrm{S\ cm^2\ mol^{-1}})$ vs $\mathrm{C^{1/2}\ (mol\ L^{-1})^{1/2}}$; curve A falls steeply from about 400 at very low concentration, curve B decreases slowly and nearly linearly from about 200]

The standard reduction potentials at 298 K for the following half cells are given below : $$\mathrm{Cr_2O_7^{2-} + 14H^+ + 6e^- \rightarrow 2Cr^{3+} + 7H_2O},\quad E^\circ = 1.33\ \mathrm{V}$$ $$\mathrm{Fe^{3+}(aq) + 3e^- \rightarrow Fe},\quad E^\circ = -0.04\ \mathrm{V}$$ $$\mathrm{Ni^{2+}(aq) + 2e^- \rightarrow Ni},\quad E^\circ = -0.25\ \mathrm{V}$$ $$\mathrm{Ag^{+}(aq) + e^- \rightarrow Ag},\quad E^\circ = 0.80\ \mathrm{V}$$ $$\mathrm{Au^{3+}(aq) + 3e^- \rightarrow Au},\quad E^\circ = 1.40\ \mathrm{V}$$ Consider the given electrochemical reactions, The number of metal(s) which will be oxidized by $\mathrm{Cr_2O_7^{2-}}$ in aqueous solution is ________.

Match List I with List II

	LIST I (Cell)		LIST II (Use/Property/Reaction)
A.	Leclanche cell	I.	Converts energy of combustion into electrical energy
B.	Ni - Cd cell	II.	Does not involve any ion in solution and is used in hearing aids
C.	Fuel cell	III.	Rechargeable
D.	Mercury cell	IV.	Reaction at anode $\mathrm{Zn \rightarrow Zn^{2+} + 2e^-}$

Choose the correct answer from the options given below:

Which out of the following is a correct equation to show change in molar conductivity with respect to concentration for a weak electrolyte, if the symbols carry their usual meaning :

In acidic medium, $\mathrm{K_2Cr_2O_7}$ shows oxidising action as represented in the half reaction :

$$\mathrm{Cr_2O_7^{2-} + XH^+ + Ye^{\ominus} \rightarrow 2A + ZH_2O}$$

X, Y, Z and A are respectively are :

Which of the following reactions are disproportionation reactions ?

(A) $\mathrm{Cu^+ \rightarrow Cu^{2+} + Cu}$

(B) $\mathrm{3MnO_4^{2-} + 4H^+ \longrightarrow 2MnO_4^- + MnO_2 + 2H_2O}$

(C) $\mathrm{2KMnO_4 \longrightarrow K_2MnO_4 + MnO_2 + O_2}$

(D) $\mathrm{2MnO_4^- + 3Mn^{2+} + 2H_2O \longrightarrow 5MnO_2 + 4H^+}$

Choose the correct answer from the options given below :

The lowest oxidation number of an atom in a compound $\mathrm{A_2B}$ is $-2$. The number of electrons in its valence shell is ________.

The potential for the given half cell at 298 K is $(-)$________ $\times 10^{-2}\,\mathrm{V}$.

$$\mathrm{2H^+_{(aq)} + 2e^- \longrightarrow H_2(g)}$$

$[\mathrm{H^+}] = 1\,\mathrm{M}$, $\mathrm{P_{H_2}} = 2$ atm

(Given : $2.303\mathrm{RT/F} = 0.06\ \mathrm{V}$, $\log 2 = 0.3$)

The amount of electricity in Coulomb required for the oxidation of 1 mol of $\mathrm{H_2O}$ to $\mathrm{O_2}$ is ________ $\times 10^5$ C.

Consider the following redox reaction :

$$\mathrm{MnO_4^- + H^+ + H_2C_2O_4 \rightleftharpoons Mn^{2+} + H_2O + CO_2}$$

The standard reduction potentials are given as below $\left(E^\circ_{\text{red}}\right)$ :

$$E^\circ_{\mathrm{MnO_4^-/Mn^{2+}}} = +1.51\ \mathrm{V}$$

$$E^\circ_{\mathrm{CO_2/H_2C_2O_4}} = -0.49\ \mathrm{V}$$

If the equilibrium constant of the above reaction is given as $K_{eq} = 10^x$, then the value of $x =$ ________ (nearest integer)

From the given list, the number of compounds with +4 oxidation state of Sulphur is ________.

$\mathrm{SO_3,\ H_2SO_3,\ SOCl_2,\ SF_4,\ BaSO_4,\ H_2S_2O_7}$

The mass of silver (Molar mass of Ag : $108\ \mathrm{g\,mol^{-1}}$) displaced by a quantity of electricity which displaces 5600 mL of $\mathrm{O_2}$ at S.T.P. will be ________ g.

Chlorine undergoes disproportionation in alkaline medium as shown below :

$$\mathrm{a\, Cl_{2(g)} + b\, OH^-_{(aq)} \rightarrow c\, ClO^-_{(aq)} + d\, Cl^-_{(aq)} + e\, H_2O_{(l)}}$$

The values of a, b, c and d in a balanced redox reaction are respectively :

The mass of zinc produced by the electrolysis of zinc sulphate solution with a steady current of 0.015 A for 15 minutes is ________ $\times 10^{-4}$ g.

(Atomic mass of zinc = 65.4 amu)

$$\mathrm{2MnO_4^- + bI^- + cH_2O \rightarrow x\,I_2 + y\,MnO_2 + z\,\overline{O}H}$$

If the above equation is balanced with integer coefficients, the value of z is ________.

Reduction potential of ions are given below:

$\mathrm{ClO_4^-}$	$\mathrm{IO_4^-}$	$\mathrm{BrO_4^-}$
$\mathrm{E^\circ = 1.19\ V}$	$\mathrm{E^\circ = 1.65\ V}$	$\mathrm{E^\circ = 1.74\ V}$

The correct order of their oxidising power is :

Total number of species from the following which can undergo disproportionation reaction is ________.

$$\mathrm{H_2O_2,\ ClO_3^-,\ P_4,\ Cl_2,\ Ag,\ Cu^{+1},\ F_2,\ NO_2,\ K^+}$$

Identify the factor from the following that does not affect electrolytic conductance of a solution.

One Faraday of electricity liberates $x \times 10^{-1}$ gram atom of copper from copper sulphate. $x$ is ________.

Given below are two statements :

Statement I : $\mathrm{S_8}$ solid undergoes disproportionation reaction under alkaline conditions to form $\mathrm{S^{2-}}$ and $\mathrm{S_2O_3^{2-}}$.

Statement II : $\mathrm{ClO_4^-}$ can undergo disproportionation reaction under acidic condition.

In the light of the above statements, choose the most appropriate answer from the options given below :

The values of conductivity of some materials at 298.15 K in $\mathrm{S\ m^{-1}}$ are $2.1 \times 10^{3}$, $1.0 \times 10^{-16}$, $1.2 \times 10$, $3.91$, $1.5 \times 10^{-2}$, $1 \times 10^{-7}$, $1.0 \times 10^{3}$. The number of conductors among the materials is ________.

Number of moles of $\mathrm{H^+}$ ions required by 1 mole of $\mathrm{MnO_4^-}$ to oxidise oxalate ion to $\mathrm{CO_2}$ is _______.