Zinc leaves behind the electrons on Electrode A during the reaction giving a negative charged whereas the Copper deposits on the Electrode B with positive charge. The polarity of electrode A...
Why is alternating current used for measuring the resistance of an electrolytic solution?
The concentration of ions is kept constant with the alternating current whereas the concentration of ion changes a lot in the direct current. So, the alternating current is used for measuring the...
A galvanic cell has an electrical potential of 1.1V. If an opposing potential of 1.1V is applied to this cell, what will happen to the cell reaction and current flowing through the cell?
If the opposing potential is equal to electrical potential, then the cell reaction and the current flow through the cell will be stopped leading to no chemical reaction.
How will the pH of brine (aq. NaCl solution) be affected when it is electrolyzed?
Reaction on Cathode - H2O(l ) + e–→ 1/2 H2(g) + OH– (aq) Reaction on Anode - Cl– (aq) → 1/2 Cl2(g) + e– Complete Reaction: NaCl(aq)+H2O(l)→NaOH(aq)+H2(g)+Cl2(g) NaOH turns the brine solution basic...
Unlike dry cell, the mercury cell has a constant cell potential throughout its useful life. Why?
The electrolyte is not consumed in the cell and so the current gets delivered at a constant potential till the end. The reaction contains no ions whose concentration can change over time. Thus, the...
Solutions of two electrolytes ‘A’ and ‘B are diluted. The of ‘B’ increases 1.5 times while that of A increases 25 times. Which of the two is a strong electrolyte? Justify your answer.
Electrolyte B - strong electrolyte During dilution the number of ions remains the same and the interionic attraction decreases. Thus, the increase in Λm is small.
When acidulated water (dil.H2SO4 solution) is electrolysed, will the pH of the solution be affected? Justify your answer.
Reaction on Anode - 2H2O(l)→ O2(g) + 4H+ (aq) + 4e– Reaction on Cathode - 4H+ + 4e-→ 2H2 Complete Reaction: 2H2O(l) → O2(g) + 2H2(g) The pH will not be affected and stays the same.
In an aqueous solution, how does specific conductivity of electrolytes change with the addition of water?
In an aqueous solution, when water is added the electrolyte gets diluted thus leading to the decrease in the specific conductivity of the electrolytes.
Which reference electrode is used to measure the electrode potential of other electrodes?
The reference electrode which is used to measure the electrode potential of other electrodes is the Standard hydrogen electrode (SHE) which has a value of zero.
Consider a cell given: Cu|Cu2+|| Cl—|Cl2, Pt Write the reactions that occur at anode and cathode.
Reaction in Anode: Oxidation half-cell Cu(s) → Cu2+ + 2e- Reaction in Cathode: Reduction half-cell Cl2(g)+ 2e-→ 2Cl- Hence, the anode Cu gets oxidised in this cell reaction.
Write the Nernst equation for the cell reaction in the Daniel cell. How will the ECell be affected when the concentration of Zn2+ ions is increased?
Nernst Equation: Ecell = E°cell – RT[Zn2+]/ nF[Cu2+] Galvanic cell reaction: Zn(s)|Zn2+(aq)||Cu2+(aq)|Cu(s) Reaction in Anode: oxidation half-cell Zn(s) → Zn2+ (aq)+ 2e Reaction in Cathode:...
What advantage do the fuel cells have over primary and secondary batteries?
Advantages of Fuel cells: 1.Fuel cells can convert the energy of combustion of fuels like hydrogen, methanol into electrical energy. 2.Fuel cells can run continuously as long as reactants are...
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?
While discharging the battery, the water dilutes the concentration of the dilute sulphuric acid which leads to a decrease in the density of the solution. Reaction Involved: Pb(s)+PbO2(s)+2H2SO4(aq)→...
Why on dilution the ˄m of CH3COOH increases drastically, while that of CH3COONa increases gradually?
Weak Electrolyte: CH3COOH Strong Electrolyte: CH3COONa . When diluted, the dissociation degree increases, and the number of ions present also increases which leads to the drastic increase of CH3COOH...
What is electrode potential?
Electrode potential is the potential difference which is developed between the electrode and the electrolyte.
Value of standard electrode potential for the oxidation of Cl– ions is more positive than that of water, even then in the electrolysis of aqueous sodium chloride, why is Cl–oxidised at anode instead of water?
The oxidation of water to oxygen is kinetically not good and requires a lot of energy which is said to have more energy. What can be very powerful is the excess energy needed to drive the reaction...
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 the same or different? Explain your answer.
W = itE/96500 W = 1×10×60×31.75/96500 Equivalent mass of Cu2+ and Ag+ is different so that the mass of copper and silver deposited will not be same.
What does the negative sign in the expression E°Zn2+/Zn = -0.76V mean?
The disadvantage is that hydrogen gas is much more stable than reduced species. Here, the reduced form (Zn) is unstable. It is difficult to reduce Zn2 + to Zn. Therefore, distortion is more likely...
Under what condition is ECell = 0 or ΔrG = 0?
Electrolysis happens when a redox reaction happens. On equilibrium, the cell is completely depleted, and the cell's energy drops to zero. ∆rG= -nF E cell =0
Can E°cell or ΔrG° for cell reaction ever be equal to zero?
A cell of E ° or G G ° cannot be equal to zero. The only standard electrode power is randomly assigned is the standard hydrogen electrode (SHE). As everything else is measured in relation to SHE;...
Can absolute electrode potential of an electrode be measured?
No. It cannot be measured. We can only estimate the electrode power difference between two and a half cells. We can also estimate the potential electrode differences associated with a standard...
For the given cell, Mg|Mg2+|| Cu2+|Cu
(i) Mg is cathode (ii) Cu is cathode (iii) The cell reaction is Mg + Cu2+ → Mg2+ + Cu (iv) Cu is the oxidising agent Correct Answers: (ii) Cu is cathode (iii) The cell reaction is Mg + Cu2+ →...
Molar conductivity of ionic solution depends on ___________.
(i) temperature. (ii) distance between electrodes. (iii) the concentration of electrolytes in solution. (iv) the surface area of electrodes. Correct Answers: (i) temperature. (iii) the...
Conductivity κ , is equal to ____________.
(i) 1/R l/A (ii) G*/R (iii) ˄m (iv) l/A Correct Answers: (i) 1/R l/A (ii) G*/R Explanation: Conductivity κ , is equal to 1/R l/A & G*/R
What will happen during the electrolysis of an aqueous solution of CuSO4 in the presence of Cu electrodes?
(i) Copper will deposit at the cathode. (ii) Copper will dissolve at the anode. (iii) Oxygen will be released at anode. (iv) Copper will deposit at the anode. Correct Answers: (i) Copper will...
What will happen during the electrolysis of an aqueous solution of CuSO4 by using platinum electrodes?
(i) Copper will deposit at the cathode. (ii) Copper will deposit at the anode. (iii) Oxygen will be released at anode. (iv) Copper will dissolve at the anode Correct Answers: (i) Copper will...
˄0m(H2O) is equal to ______________.
(i) ˄0m(HCl) + ˄0m(NaOHl) – ˄0m(NaCl) (ii) ˄0m(HNO3) + ˄0m(NaNO3) – ˄0m(NaOH) (iii) ˄0m(HNO3) + ˄0m(NaOH) – ˄0m(NaNO3) (iv) ˄0m(NH4OH) + ˄0m(HCl) – ˄0m(NH4Cl) Correct Answers: (i) ˄0m(HCl) +...
Conductivity of an electrolytic solution depends on ____________.
(i) nature of electrolyte. (ii) the concentration of electrolyte. (iii) power of AC source. (iv) distance between the electrodes. Correct Answers: (i) nature of electrolyte. (ii) the...
E°Cell = 1.1V for Daniel cell. Which of the following expressions are correct description of state of equilibrium in ths cell?
(i) 1.1 = Kc (ii) 2.303RT/2F logKc = 1.1 (iii) log Kc = 2.2/0.059 (iv) log Kc = 1.1 Correct Answers: (ii) 2.303RT/2F logKc = 1.1 (iii) log Kc = 2.2/0.059
E°Cell for some half cell reactions are given below. Based on these mark the correct answer.
(a) H+(aq) + e– →1/2H2(g) ; E°cell = 0.00V (b) 2H2O (l) → O2 (g) + 4H+(aq) + 4e–: E°cell = 1.23V (c) 2SO42– (aq) → S2O82– (aq) + 2e– ; E°cell = 1.96V (i) In dilute sulphuric acid solution, hydrogen...
The positive value of the standard electrode potential of Cu2+/Cu indicates that ____________.
(i) this redox couple is a stronger reducing agent than the H+/H2 couple. (ii) this redox couple is a stronger oxidising agent than H+/H2. (iii) Cu can displace H2 from acid. (iv) Cu cannot displace...
In the electrolysis of aqueous sodium chloride solution which of the half cell reaction will occur at anode?
(i) Na+(aq) + e– → Na (s); E°Cell = –2.71V (ii) 2H2O (l) → O2(g) + 4H+(aq) + 4e– : E°Cell = 1.23V (iii) H+(aq) + e–→1/2H2 (g); E°Cell = 0.00V (iv) Cl–(aq) →1/2Cl2(g) + e– ; E°Cell = 1.36V ...
˄0m(NH4OH) is equal to ______________.
(i) ˄0m(NH4OH) + ˄0m(NH4Cl) – ˄0(HCl) (ii) ˄0m(NH4Cl) + ˄0m(NaOH) – ˄0(NaCl) (iii) ˄0m(NH4Cl) + ˄0m(NaCl) – ˄0(NaOH) (iv) ˄0m(NaOH) + ˄0m(NaCl) – ˄0(NH4Cl) Correct Answer: (ii) ˄0m(NH4Cl) +...
While charging the lead storage battery ______________.
(i) PbSO4 anode is reduced to Pb (ii) PbSO4 cathode is reduced to Pb (iii) PbSO4 cathode is oxidised to Pb (iv) PbSO4 anode is oxidised to PbO2 Correct Answer: (i) PbSO4 anode is reduced to...
The cell constant of a conductivity cell _____________.
(i) changes with the change of electrolyte. (ii) changes with the change of concentration of electrolyte. (iii) changes with the temperature of the electrolyte. (iv) remains constant for a cell....
The quantity of charge required to obtain one mole of aluminium from Al2O3 is ___________.
(i) 1F (ii) 6F (iii) 3F (iv) 2F Correct Answer: (iii) 3F Explanation: 3F of charge is required to obtain 1 mole of Al from the Al2O3
Use the data of Q.8 and find out the most stable oxidised species.
(i) Cr3+ (ii) MnO4– (iii) Cr2O72– (iv) Mn2+ Correct Answer: (i) Cr3+ Explanation: Cr3+ is the most stable oxidised species when compared to the rest of the options.
Use the data given in Q.8 and find out the most stable ion in its reduced form.
(i) Cl– (ii) Cr3+ (iii) Cr (iv) Mn2+ Correct Answer: (iv) Mn2+ Explanation: Mn2+ in its reduced form is observed to be more stable.
Using the data given in Q.8 find out in which option the order of reducing power is correct.
(i) Cr3+ < Cl–< Mn2+ < Cr (ii) Mn2+ < Cl–< Cr3+ < Cr (iii) Cr3+ < Cl–< Cr2O72– < MnO4– (iv) Mn2+ < Cr3+ < Cl–< Cr Correct Answer: (ii) Mn2+ < Cl–<...
Use the data given in Q.8 and find out which of the following is the strongest oxidising agent.
(i) Cl– (ii) Mn2+ (iii) MnO4– (iv) Cr3+ Correct Answer: (iii) MnO4– Explanation: The higher the value of the normal reduction of the strength of the metal ion, the higher will be its...
Using the data given below to find out the strongest reducing agent.
EᶱCr2O72-/Cr3+ = 1.33V EᶱMnO4–/Mn2+ = 1.51V EᶱCl2/Cl– = 1.36V EᶱCr3+/Cr = -0.74V (i) Cl– (ii) Cr (iii) Cr3+ (iv) Mn Correct Answer: (ii) Cr Explanation: The most powerful reducing agent is...
Which of the statements about solutions of electrolytes is not correct?
(i) The conductivity of the solution depends upon the size of ions. (ii) Conductivity depends upon the viscosity of the solution. (iii) Conductivity does not depend upon solvation of ions present in...
An electrochemical cell can behave like an electrolytic cell when ____________.
(i) Ecell = 0 (ii) Ecell > Eext (iii) Eext > Ecell (iv) Ecell = Eext Correct Answer: (iii) Eext > Ecell
Which of the following statement is not correct about an inert electrode in a cell?
(i) It does not participate in the cell reaction. (ii) It provides surface either for oxidation or for the reduction reaction. (iii) It provides a surface for conduction of electrons. (iv) It...
The difference between the electrode potentials of two electrodes when no current is drawn through the cell is called ___________.
(i) Cell potential (ii) Cell emf (iii) Potential difference (iv) Cell voltage Correct Answer: (ii) Cell emf Explanation: Electromotive force or e.m.f. is the power provided by the cell or...
Which of the following statement is correct?
(i) ECell and ∆rG of cell reaction both are extensive properties. (ii) ECell and ∆rG of cell reaction both are intensive properties. (iii) ECell is an intensive property while ∆rG of cell reaction...
Electrode potential for Mg electrode varies according to the equation EMg2+/Mg = EᶱMg2+/Mg – 0.0591/2 log1/[Mg2+ ] . The graph of EMg2+/Mg Vs log [Mg2+] is
Correct Answer: Option (ii)
Which cell will measure standard electrode potential of copper electrode?
(i) Pt (s) H2(g,0.1 bar) H+ (aq.,1 M) Cu2+(aq.,1M) Cu (ii) Pt(s) H2 (g, 1 bar) H+ (aq.,1 M) Cu2+ (aq.,2 M) Cu (iii) Pt(s) H2(g, 1 bar) H+ (aq.,1 M) Cu2+ (aq.,1 M) Cu (iv) Pt(s) H2 (g, 1 bar)...