Electrochemistry · Chemistry · COMEDK

The $E_{M^{3+} / M^{2+}}^o$ values for $\mathrm{Cr}, \mathrm{Mn}, \mathrm{Fe}$ and Co are $-0.41,+1.57,+0.77$ and +1.97 V respectively.

For which of these metals, the change in oxidation state from +2 to +3 is the easiest?

What is the standard electrode potential at 298 K for the reaction: $\mathrm{Cu}^{2+}+1 \mathrm{e}-\rightarrow \mathrm{Cu}^{+1}$ ?

Given: $\mathrm{E}_0 \mathrm{Cu}^{+1} / \mathrm{Cu}=0.5 \mathrm{~V} \quad \& \quad \mathrm{E}_0 \mathrm{Cu}^{+2} / \mathrm{Cu}=0.335 \mathrm{~V}$

The Standard Reduction potential at $25^{\circ} \mathrm{C}$ for $\left(\mathrm{MnO}_4\right)^{-1} / \mathrm{H}^{+}$is +1.49 V . The $\mathrm{E}^0$ values for four Metal ions :

(a). $\mathrm{Co}^{3+} / \mathrm{Co}^{2+}$

(b). $\mathrm{Cr}^{3+} / \mathrm{Cr}$

(c). $\mathrm{Au}^{3+} / \mathrm{Au}$ and

(d). $\mathrm{Ag}^{+} / \mathrm{Ag}$

are $+1.81 \mathrm{~V},-0.74 \mathrm{~V},+1.50 \mathrm{~V}$ and +0.8 V respectively. Identify two of them which cannot be oxidised by $\left(\mathrm{MnO}_4\right)^{-1} / \mathrm{H}^{+}$

Two statements, one Assertion and the other Reason are given. Choose the correct option.

Assertion: For strong electrolytes the plot of Molar conductivity versus Concentration gives a straight line with slope equal to +A and intercept equal to $\lambda_{\mathrm{m}}$

Reason: For strong electrolytes, $\lambda_{\mathrm{m}}$ increases slowly with dilution due to increase in the distance between the ions and increase in ionic mobility

$$\mathrm{E}^0\left(\mathrm{Fe}^{3+} / \mathrm{Fe}^{2+}\right)=0.771 \mathrm{~V}$$

Identify the correct statement regarding corrosion of iron rod left exposed to atmosphere.

Given below are 2 statements: Assertion and Reason. Choose the correct option.

Assertion: When Molar conductivity for a strong electrolyte is plotted versus $$\sqrt{C}(\mathrm{~mol} / \mathrm{L})^{1 / 2}$$, a straight line is obtained with intercept equal to Molar conductivity at infinite dilution for the electrolyte and Slope equal to $$-\mathrm{A}$$. All electrolytes of a given type have the same $$\mathrm{A}$$ value.

Reason: At infinite dilution, strong electrolytes of the same type will have different number of ions due to incomplete dissociation.

What is the quantity of charge, in Faraday units, required for the reduction of 3.5 moles of $$\mathrm{Cr}_2 \mathrm{O} 7^{2-}$$ in acid medium?

A dry cell consists of a moist paste of $$\mathrm{NH}_4 \mathrm{Cl}$$ and $$\mathrm{ZnCl}_2$$ contained in a $$\mathrm{Zn}$$ casing which encloses a Carbon rod surrounded by black $$\mathrm{MnO}_2$$ paste. What is the role of $$\mathrm{ZnCl}_2$$ in it?

A current of 3.0A is passed through 750 ml of 0.45 M solution of CuSO$$_4$$ for 2 hours with a current efficiency of 90%. If the volume of the solution is assumed to remain constant, what would be the final molarity of CuSO$$_4$$ solution?

Arrange the following redox couples in the increasing order of their reducing strength:

$$\begin{array}{ll} {[\mathrm{A}]=\mathrm{Cu} / \mathrm{Cu}^{2+}} & \mathrm{E}^0=-0.34 \mathrm{~V} \\ {[\mathrm{~B}]=\mathrm{Ag} / \mathrm{Ag}^{+}} & \mathrm{E}^0=-0.8 \mathrm{~V} \\ {[\mathrm{C}]=\mathrm{Ca} / \mathrm{Ca}^{2+}} & \mathrm{E}^0=+2.87 \mathrm{~V} \\ {[\mathrm{D}]=\mathrm{Cr} / \mathrm{Cr}^{3+}} & \mathrm{E}^0=+0.74 \mathrm{~V} \end{array}$$

When 0.1 mole of $$\mathrm{MnO}_4{ }^{2-}$$ is oxidised, the quantity of electricity required to completely oxidise $$\mathrm{MnO}_4{ }^{2-}$$ to $$\mathrm{MnO}_4^{-}$$ is

Identify the incorrect statement among the following.

$$\mathrm{Cu}^{+}$$ undergoes disproportionation, according to the equation,

$$ 2 \mathrm{Cu}^{+} \rightleftharpoons \mathrm{Cu}^{2+}+\mathrm{Cu} $$

The $$\mathrm{E}^{\circ}$$ value for the reaction is:

$$[\mathrm{E}_{\mathrm{Cu}^{2+} / \mathrm{Cu}}^{\mathrm{o}}=0.34 \mathrm{~V} \text { and } \mathrm{E}_{\mathrm{Cu}^{2+} / \mathrm{Cu}^{+}}^{\mathrm{O}}=0.15 \mathrm{~V}]$$

The $$\mathrm{E}^{\circ}$$ values of $$\mathrm{A} . \mathrm{B}$$ and $$\mathrm{C}$$ are given. Which element/(s) is/(are) good for coating the surface of iron to prevent corrosion? Given: $$[\mathrm{E}_{\mathrm{Fe}^{2+} / \mathrm{Fe}}^0=-0.44 \mathrm{~V} ; \quad \mathrm{E}_{\mathrm{A}^{2+} / \mathrm{A}}^0=-2.37 \mathrm{~V} ; \quad \mathrm{E}_{\mathrm{B}^{2+} / \mathrm{B}}^0=-0.15 \mathrm{~V} ; \quad \mathrm{E}_{\mathrm{C}^{2+} / \mathrm{C}}^0=+0.34 \mathrm{~V}]$$

The limiting molar conductivity of $$\mathrm{NH}_4 \mathrm{OH}$$ is $$238 \mathrm{~S} \mathrm{~cm}^2 \mathrm{~mol}^{-1}$$. At $$25^{\circ} \mathrm{C}$$, molar conductance of $$0.1 \mathrm{M}$$ aqueous solution of ammonium hydroxide is $$9.54 \mathrm{~S} \mathrm{~cm}^2 \mathrm{~mol}^{-1}$$. The degree of ionisation of $$\mathrm{NH}_4 \mathrm{OH}$$ at the same concentration and temperature is:

What would be the EMF of the cell in which the following reaction occurs:

$$\begin{aligned} & \mathrm{Cd}(\mathrm{S})+2 \mathrm{H}^{+} \rightarrow \mathrm{Cd}^{2+}+\mathrm{H}_{2(\mathrm{~g})} \\ & {\left[\mathrm{H}^{+}\right]=0.02 \mathrm{M} \quad \mathrm{E}^0\left(\mathrm{Cd}^{2+} / \mathrm{Cd}\right)=-0.4 \mathrm{~V},\left[\mathrm{Cd}^{2+}\right]=0.01 \mathrm{M} \text { and partial pressure of } \mathrm{H}_2 \text { gas }=0.8 \mathrm{~atm} .} \end{aligned}$$

Propane in presence of $$\mathrm{O}_2$$ gas undergoes complete combustion to produce $$\mathrm{CO}_2$$ and $$\mathrm{H}_2 \mathrm{O}$$. The required $$\mathrm{O}_2$$ for this combustion reaction was produced by the electrolysis of water. For what duration of time had water been electrolysed by passing $$200 \mathrm{~A}$$ current so that Oxygen gas produced could completely burn $$44 \mathrm{~g}$$ of Propane?

$$0.1 \mathrm{M}$$ solution of $$\mathrm{AgNO}_3$$ is taken in a Conductivity cell and a potential difference of $$40 \mathrm{~V}$$ is applied across the ends of a column of this solution whose diameter is $$4.0 \mathrm{~cm}$$ and length of the column is $$12 \mathrm{~cm}$$. The current used is $$0.4 \mathrm{~A}$$. The Molar conductivity of the solution is _________.

Match the chemical reactions taking place at the Anode of the cell with the correct cell in which the reaction occurs.

Given below are 4 equations showing Molar conductivities at infinite dilution of various electrolytes. Which one of them represents the correct equation?

$$\begin{aligned} & \left(\Lambda_m^0\right)_{N a B r}-\left(\Lambda_m^0\right)_{N a C l}=\left(\Lambda_m^0\right)_{\mathrm{KCl}}-\left(\Lambda_m^0\right)_{\mathrm{KBr}} \\ & \left(\Lambda_m^0\right)_{\mathrm{HCl}}+\left(\Lambda_m^0\right)_{\mathrm{KOH}}-\left(\Lambda_m^0\right)_{\mathrm{KCl}}=\left(\Lambda_m^0\right)_{\mathrm{H}_2 \mathrm{O}} \\ & \left(\Lambda_m^0\right)_{\mathrm{KBr}}-\left(\Lambda_m^0\right)_{\mathrm{NaBr}}=\left(\Lambda_m^0\right)_{\mathrm{NaBr}}-\left(\Lambda_m^0\right)_{\mathrm{Nal}} \\ & \left(\Lambda_m^0\right)_{N H_4 \mathrm{Cl}}-\left(\Lambda_m^0\right)_{\mathrm{NH}_4 \mathrm{NO}_3}=\left(\Lambda_m^0\right)_{N H_4 \mathrm{Cl}}-\left(\Lambda_m^0\right)_{N H 4 B r} \end{aligned}$$

Assuming no change in volume, the time required to obtain solution of $$\mathrm{pH}=4$$ by electrolysis of $$100 \mathrm{~mL}$$ of $$0.1 \mathrm{~M} \mathrm{~NaOH}$$ (using current $$0.5 \mathrm{~A}$$ ) will be

For a cell reaction, $$A(s)+B^{2+}(a q) \longrightarrow A^{2+}(a q)+B(s)$$; the standard emf of the cell is $$0.295 \mathrm{~V}$$ at $$25^{\circ} \mathrm{C}$$. The equilibrium constant at $$25^{\circ} \mathrm{C}$$ will be

The Molar conductivity of $$0.05 \mathrm{M}$$ solution of $$\mathrm{MgCl}_2$$ is $$194.5 \mathrm{~ohm}^{-1} \mathrm{~cm}^2$$ per mole at room temperature. A Conductivity cell with electrodes having $$3.0 \mathrm{~cm}^2$$ surface area and $$1.0 \mathrm{~cm}$$ apart is filled with the solution of $$\mathrm{MgCl}_2$$. What would be the resistance offered by the conductivity cell?

If electrolysis of water is carried out for a time duration of 2 hours, how much electric current in amperes would be required to liberate $$100 \mathrm{~ml}$$ of $$\mathrm{O}_2$$ gas measured under standard conditions of temperature and pressure?

Match the items in Column I with their description in Column II

When Lead Storage battery is in the process of getting charged which one of the following reactions takes place?

The reaction taking place in a galvanic cell is as given

$$\mathrm{A}(\mathrm{s})+\mathrm{B}^{2+}\left(\mathbf{1} \mathbf{1} \mathbf{1 0} \mathbf{0}^{-\mathrm{M}} \mathbf{M}\right) \rightarrow \mathrm{B}_{(\mathrm{s})}+\mathrm{A}^{2+}(0.1 \mathrm{M}).$$

The emf of the cell is $$+2.651 \mathrm{~V}$$. If the standard emf of the cell is $$+2.71 \mathrm{~V}$$, what is the value of $$\mathrm{X}$$ ?

What will be the emf of the following cell at 25$$^\circ$$C?

Fe/Fe$$^{2+}$$ (0.001 M) | | H$$^+$$ (0.01 M) | H$$_2$$(g) (1 Bar) | Pt(s)

$$E_{(F{e^{2+}} /Fe)}^o = - 0.44$$ V; $$E_{({H^ + }/{H_2})}^o = - 0.00$$ V

Calculate the molar conductance of 0.025 M aqueous solution of calcium chloride at 25$$^\circ$$C. The specific conductance of calcium chloride is 12.04 $$\times$$ 10$$^{-2}$$ Sm$$^{-1}$$

Given that molar conductances for Ba(OH)$$_2$$, BaCl$$_2$$ and NH$$_4$$Cl are 523.28, 280.0 and 129.8 $$\Omega^{-1}$$ cm$$^2$$ mol$$^{-1}$$ respectively. What is the molar conductivity ($$\Omega^{-1}$$ cm$$^2$$ mol$$^{-1}$$) of NH$$_4$$OH?

The specific conductivity of a solution containing 1.0 g of anhydrous BaCl$$_2$$ in 200 cm$$^3$$ of the solution has been found to be 0.0058 Scm$$^{-1}$$. The molar and equivalent conductivity of the solution respectively are