Explain how rusting of iron is envisaged as setting up of an electrochemical cell.
The water present on the surface of iron dissolves acidic oxides of air like CO2 , SO2 , etc. to form acids which dissociate to give H+ ions :
Thus, an electrochemical cell is set up on the surface.
Ferrous ions are further oxidised by atmospheric oxygen to ferric ions which combine with water to form hydrated ferric oxide, Fe2O3. xH2O, which is rust.
Calculate the potential of hydrogen electrode in contact with a solution whose pH is 10.
The positive value of the standard electrode potential of Cu+2/Cu indicates that
(a) this redox couple is a stronger reduction agent than the H/H2 couple
(b) this redox couple is a stronger oxidizing agent than H+/H2
(c) Cu can displace H2 from acid
(d) Cu cannot displace H2 from acid
Three electrolytic cells A, B, C containing solutions of ZnS04, AgNO3 and CuS04, respectively are connected in series. A steady current of 1.5 amperes was passed through them until 45 g of silver deposited at the cathode of call B. How long did the current flow? What mass of copper and zinc were deposited?
When acidulated water (dil. H2SO4 solution) is electrolysed, will the pH of the solution be affected? Justify your answer.
Assertion (A): E , increases with increase in concentration of Ag+ ions.
Ag / Ag+
Reason (R): E + has a positive value.
Ag /Ag
The molar conductivity of 0.025 mol L-1 methanoic acid is 46.1 S cm2 mol-1. Calculate its degree of dissociation and dissociation constant Given λ °(H+)=349.6 S cm2 mol-1 andλ °(HCOO-) = 54.6 S cm2 mol-1
The resistance of a conductivity cell containing 0.001 M KCI solution at 298 K is 1500 Ω What is the cell constant if conductivity of 0.001 M KCI solution at 298 K is 0.146 x 10-3 S cm-1?
The conductivity of 0.20 M solution of KCl at 298 K is 0.0248 S cm-1. Calculate its molar conductivity.
Aqueous copper sulphate solution and aqueous silver nitrate solution are electrolysed by 1 ampere current for 10 minutes in separate electrolytic cells. Will the mass of copper and silver deposited on the cathode be same or different? Explain your answer.
Consider a cell given below:
Cu |Cu2+ || Cl |Cl2, Pt
Write the reactions that occur at anode and cathode.
Arrange the following metals in the order in which they displace each other from the solution of their salts: Al, Cu, Fe, Mg and Zn.
A solution of Ni(N03)2 is electrolyzed between platinum electrodes using a current of 5 amperes for 20 minutes. What mass of Ni is deposited at the cathode?
Write the Nemst equation for the cell reaction in the Daniell cell. How will the Ecell be affected when concentration of Zn2+ ions is increased?
Consider the figure given below and answer the questions (i) to (vi) that follow.
(i) Redraw the diagram to show the direction of electron flow.
(ii) Is silver plate anode or cathode?
(iii)What will happen if salt bridge is removed?
(iv)When will the cell stop functioning?
(v)How will concentration of Zn+2 cell functions?
(vi)How will the concentration of Zn+2 ions and Ag+ ions be affected after the cell becomes ‘dead'?
The cell in which the following reaction occurs: 2Fe3+ (aq) + 2I– (aq) —> 2Fe2+ (aq) +I2 (s) has E °cell=0.236 V at 298 K. Calculate the standard Gibbs energy and the equilibrium constant of the cell reaction.
How much charge is required for the following reductions:
(i) 1 mol of Al3+ to Al?
(ii) 1 mol of Cu2+ to Cu ?
(iii) 1 mol of Mn04- to Mn2+?
Predict the products of electrolysis in each of the following.
(i) An aqueous solution of AgNO3 with silver electrodes.
(ii) An aqueous solution of AgNO3 with platinum electrodes.
(iii) A dilute solution of H2S04 with platinum electrodes.
(iv) An aqueous solution of CuCl2 with platinum electrodes.
Write the cell reaction of a lead storage battery when it is discharged. How does the density of the electrolyte change when the battery is discharged?
Assertion (A): Ecell should have a positive value for the cell to function. Reason (R). Ecadlode Eanode
Given the standard electrode potentials, K+/K=-2. 93 V, Ag+/Ag = 0.80 V, Hg2+/Hg =0.79V, Mg2+/Mg=-2.37V, Cr3+/Cr=0.74V.
Arrange these metals in their increasing order of reducing power.
Consultthe table of standard electrode potentials and suggest three substances that can oxidise ferrous ions under suitable conditions.
What will happen during the electrolysis of aqueous solution of CuSO4 in the presence of Cu electrodes?
(a) Copper will deposit at cathode.
(b) Copper will dissolve at anode.
(c) Oxygen will be released at anode.
(d) Copper will deposit at anode.
Assertion (A): Current stops flowing when Ecell = 0.
Reason (R): Equilibrium of the cell reaction is attained.
If a current of 0.5 ampere flows through a metallic wire for 2 hours, then how many electrons would flow through the wire?
Consider the reaction: Cr2O72--+ 14H+ + 6e- -> 2Cr3+ + 7H2O What is the quantity of electricity in coulombs needed to reduce 1 mol of Cr2O72- ?
In the button cells widely used in watches and other devices the following reaction takes place:
How much electricity in terms of Faraday is required to produce .
(i) 20.0 g of Ca from molten CaCl2?
(ii) 40.0 g of Al from molten Al203?
How much electricity is required in coulomb for the oxidation of (i) 1 mol of H2O to 02 (ii) 1 mol of FeO to Fe203
The quantity of charge required to obtain one mole of aluminium from
Al2O3 is (a) IF (b) 6F (c) 3F (d) 2F
In the electrolysis of aqueous sodium chloride solution, which of the half-cell reaction will occur at anode?
E °en = 1.1 V for Daniell cell. Which of the following expressions are correct description of state of equilibrium in this cell?
mean? Zn /Zn
for cell reaction ever be equal to zero?
