Electrochemistry

Class 12th Chemistry – 3 Electrochemistry MCQs

Faraday published his results during ____in the form of Faraday’s two laws of ____.

Correct! Wrong!

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Faraday published his results during 1833-34 in the form of Faraday’s two laws of electrolysis. Michael Faraday was the first scientist who described the quantitative aspects of electrolysis.

Corrosion is a/an ____ phenomenon.

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Corrosion is an electrochemical phenomenon. Since corrosion involves redox reaction with release of energy used for non-spontaneous chemical reaction, it is an electrochemical phenomenon.

____ is used for galvanization because it is more reactive than iron and will consequently ____ itself, leaving the iron untouched by rust.

Correct! Wrong!

Corrosion is also prevented by covering the surface of the metal by other inert metals. Zinc is used for galvanization because it is more reactive than iron and will consequently sacrifice itself, leaving the iron untouched by rust. Tin is less reactive than iron, while sodium is highly reactive and catches fire when subjected to air and moisture.

The difference in limiting molar conductivity of the electrolytes NaX and KX for any X is ____.

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The difference in limiting molar conductivity of the electrolytes NaX and KX for any X is nearly constant. At 298 K, Eom (KCl) - Eom (NaCl) = Eom (KBr) - Eom (NaBr) = Eom (KI) - Eom (NaI) ≈ 23.4 S cm2 mol–1 Kohlrausch observed certain regularities for a number of strong electrolytes.

The change in molar conductivity for weak electrolytes with dilution is due to ____.

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The change in molar conductivity for weak electrolytes with dilution is due to increase in degree of dissociation. Weak electrolytes have lower degree of dissociation at higher concentrations and hence for such electrolytes, the change in Λm with dilution is due to increase in the degree of dissociation and consequently the number of ions in total volume of solution that contains 1 mol of electrolyte.

Electrical conductance through metals is called ____ or ____conductance and is due to the movement of ____.

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Electrical conductance through metals is called metallic or electronic conductance and is due to the movement of electrons. The conductance of electricity by ions present in the solutions is called electrolytic or ionic conductance.

In a Daniel cell of Cu2+ and Zn2+ ions, E(cell) ____ with increase in the concentration of Cu2+ ions and ____with increase in the concentration of Zn2+ ions.

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In Daniel cell of Cu2+ and Zn2+ ions, E(cell) increases with increase in the concentration of Cu2+ ions and decreases with increase in the concentration of Zn2+ ions. E(cell) depends on the concentration of both Cu2+ and Zn2+ ions.

1 Faraday always liberates/deposits ____ of the substance on electrolysis.

Correct! Wrong!

1 Faraday always liberates/deposits 1 gram equivalent of the substance on electrolysis.

____ electrodes are used as inert electrodes.

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Platinum is used as inert electrode. Inert electrodes do not participate in the reaction but provide their surface for oxidation or reduction reactions and for the conduction of electrons. Gold is also used as inert electrode.

The charge on 1g ions of Mn4+ion is ____.

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The charge on 1g of Mn4+ ion is 3.85 × 105 C. Charge on one ion of Mn4+ = 4 × 1.6 × 10-19 C Thus, charge on one g ion of Mn4- = 4 × 1.6 10-19 × 6.02 × 1023 = 3.85 × 105 C.

Magnesium is used as a ____ electrode to prevent corrosion of iron pipes.

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Magnesium is used as a sacrificial electrode to prevent corrosion. An electrochemical method is to provide a sacrificial electrode of another metal (like Mg, Zn, etc.) which corrodes itself but saves the other object.

The standard electrode potential of Li+/Li at 298 K is ______.

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The standard electrode potential of Li+/Li at 298 K is -3.05 V. Lithium has the lowest electrode potential indicating that lithium ion is the weakest oxidising agent, while lithium metal is the most powerful reducing agent in an aqueous solution.

The competing reduction reaction at the cathode during the electrolysis of aqueous sodium chloride is ____.

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The competing reduction reaction at the cathode during the electrolysis of aqueous sodium chloride is H+ (aq) + e– → ½ H2 (g). The reaction with higher value of E0 is preferred.

In corrosion, the metal is oxidised by ____ to oxygen and formation of ____.

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In corrosion, the metal is oxidised by loss of electrons to oxygen and formation of oxides.

The amount of chemical reaction which occurs at any electrode during ____ by a current is ____to the quantity of electricity passed through the electrolyte.

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The amount of chemical reaction which occurs at any electrode during electrolysis by a current is proportional to the quantity of electricity passed through the electrolyte. This is Faraday's first law of electrolysis. The electrolyte used may be solution or melt.

The cell potential is the difference between the electrode potentials of the cathode and anode and is called the ____of the cell, when no current is drawn through the cell.

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The cell potential is the difference between the electrode potentials of the cathode and anode and is called the cell electromotive force of the cell, when no current is drawn through the cell. It is also represented as emf. The cell potential is measured in volts.

In a galvanic cell, the half-cell in which oxidation takes place is called ____.

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In a galvanic cell, the half-cell in which oxidation takes place is called anode. It has a negative potential with respect to the solution. The other half-cell in which reduction takes place is called cathode and it has a positive potential with respect to the solution. Thus, there exists a potential difference between the electrodes.

During the electrolysis of aqueous sodium chloride, oxidation of chloride ion is preferred at anode due to ____.

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During the electrolysis of aqueous sodium chloride, oxidation of chloride ion is preferred at anode due to over-potential of oxygen. The reaction at anode with lower value of Eo is preferred and therefore, water should get oxidised in preference to Cl (aq). However, on account of over-potential of oxygen, reaction Cl- (aq) → 1/2Cl2 (g) + e- is preferred.

The cell potential of a cell that has standard hydrogen electrode as one of the electrode is equal to ____ as the potential of standard hydrogen electrode is ____.

Correct! Wrong!

The cell potential is equal to standard electrode potential, as standard hydrogen potential is zero. The cell potential is given by Eo = EoR - EoL As EoL for standard hydrogen electrode is zero, Eo = EoR – 0 = EoR. Standard hydrogen potential is zero at all temperatures. It cannot be unity.

The products of electrolysis of molten sodium chloride are ____ and ____.

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The products of electrolysis of molten sodium chloride are sodium metal and chlorine gas. The cation Na+ is reduced at the cathode Na+ + e → Na and one anion Cl is oxidised at the anode Cl→ ½Cl2+e– to give sodium metal and chlorine gas.

The magnitude of conductivity depends mainly on ____ and the ____ at which the measurements are made.

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The magnitude of conductivity depends on nature of the material and the temperature at which the measurements are made. Depending on the magnitude of conductivity, the materials are classified in to conductors (metals), insulators (glass, ceramics), semiconductors (silicon, doped silicon) and super conductors (ceramic material, mixed oxides).

If n moles of electrons are transferred in a cell, then what is the quantity of charge flowing through the wire?

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For the transfer of 1 mole of electrons, the quantity of electricity flowing = 1F then, For the transfer of n mole of electrons, the quantity of electricity flowing = nF.

During the electrolysis of aqueous sodium chloride solution, the products obtained are ____.

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During the electrolysis of aqueous sodium chloride solution, the products are NaOH, Cl2 and H2. Besides Na+ and Cl ions, we also have H+ and OH ions along with the solvent molecules, H2O in aqueous sodium chloride solution electrolyses to give the products NaOH, Cl2 and H2.

The conductivity of pure water is ____.

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The conductivity of pure water is 3.5 × 10-5 Sm-1. Pure water has small amounts of hydrogen and hydroxyl ions (~10–7M) which lend it very low conductivity (3.5 × 10–5 S m–1).

The two different portions of the Daniell cell on which the two half reactions occurs are called as ____.

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The two different portions of the Daniell cell on which the two half reactions occurs are called as half-cells. It is also known as redox couples. The copper electrode of the Daniell cell is called as reduction half cell and the zinc electrode is called as oxidation half cell, where the respective reactions take place.

The corrosion of metal is prevented by covering the surface with chemical like ____.

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The corrosion of metal is prevented by covering the surface with chemical like bisphenol. Bisphenol is commonly used to prevent corrosion in the cans used for storage of food and beverages.

The electrode potential at any given concentration of Zn2+ ions is given by the expression ____.

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The electrode potential for any given concentration of Zn2+ ions is given as E(Zn2+/Zn) = Eo(Zn2+/Zn) -RT/2Fln1/[Zn2+(aq)]. This is obtained by applying Nernst equation.

The number of moles of electrons involved in the cell reaction of the cell Al/Al3+(0.01M)∥Fe2+( 0.02M)/Fe are ____.

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The cell reaction for the given cell can be written as: 2Al(s) + 3Fe2+ →2Al3+ + 3Fe(s) 6 moles of electrons are involved in the process

In the electrode reaction Mg2+ (l) + ne- → Mg(s); ____ number of mole of electrons or ____ of electricity are required for the reduction of one mole of the ions.

Correct! Wrong!

The number of mole of electrons required for the reduction of one mole of Mg2+ ions are 2e-. One mole of Mg2+ requires 2 moles of electron that is 2 Faraday.

Which of these statements is true about the expression - ΔG0= nFE0cell?

Correct! Wrong!

In an electrochemical cell, the decrease of free energy (-ΔG0)provides a measure of electrical work done (E0cell).

Class 12th Chemistry - 3 Electrochemistry MCQs
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Class 12th Chemistry - 3 Electrochemistry MCQs