NEET Electrochemistry — Set 4

Question 1

What is the cell constant if the resistance of a 0.05 M KCl solution is 100 Ω and its conductivity is 0.0065 S cm$^{-1}$?

Accepted Answer

$ \kappa = \frac{\text{cell constant}}{R} $, $ 0.0065 = \frac{\text{cell constant}}{100} $, cell constant = 0.65 cm$^{-1} $.

Question 2

In a mercury cell, what is the overall cell reaction?

Accepted Answer

Anode: $ Zn + 2OH^- \rightarrow ZnO + H_2O + 2e^- $. Cathode: $ HgO + H_2O + 2e^- \rightarrow Hg + 2OH^- $. Overall: $ Zn + HgO \rightarrow ZnO + Hg $.

Question 3

A cell $ Zn(s) | Zn^{2+}(0.02 \, M) || Fe^{3+}(0.05 \, M), Fe^{2+}(0.01 \, M) | Pt(s) $ operates at 298 K. What is the cell potential? (Given: $ E^\circ_{Zn^{2+}/Zn} = -0.76 \, V $, $ E^\circ_{Fe^{3+}/Fe^{2+}} = 0.77 \, V $)

Accepted Answer

$ E^\circ_{cell} = 0.77 - (-0.76) = 1.53 \, V $. $ E_{cell} = 1.53 - \frac{0.059}{1} \log \frac{[Zn^{2+}][Fe^{2+}]}{[Fe^{3+}]} = 1.53 - 0.059 \log \frac{0.02 \times 0.01}{0.05} = 1.53 + 0.0566 = 1.5866 \, V $.

NEET Chemistry: Electrochemistry — Practice Set 4

Q1. What is the cell constant if the resistance of a 0.05 M KCl solution is 100 Ω and its conductivity is 0.0065 S cm\(^{-1}\)?

Q2. In a mercury cell, what is the overall cell reaction?

Q3. A cell \( Zn(s) | Zn^{2+}(0.02 \, M) || Fe^{3+}(0.05 \, M), Fe^{2+}(0.01 \, M) | Pt(s) \) operates at 298 K. What is the cell potential? (Given: \( E^\circ_{Zn^{2+}/Zn} = -0.76 \, V \), \( E^\circ_{Fe^{3+}/Fe^{2+}} = 0.77 \, V \))

Q4. A cell \( Sn(s) | Sn^{2+}(0.001 \, M) || I_2(s) | I^-(0.02 \, M) | Pt(s) \) operates at 298 K. What is the cell potential? (Given: \( E^\circ_{Sn^{2+}/Sn} = -0.14 \, V \), \( E^\circ_{I_2/I^-} = 0.54 \, V \))

Q5. What is the standard emf of a cell with the reaction \( Mn(s) + Hg^{2+}(aq) \rightarrow Mn^{2+}(aq) + Hg(l) \)? (Given: \( E^\circ_{Mn^{2+}/Mn} = -1.18 \, V \), \( E^\circ_{Hg^{2+}/Hg} = 0.85 \, V \))

Q6. How much charge (in coulombs) is required to deposit 0.54 g of nickel from NiSO\(_4\) solution? (Atomic mass of Ni = 54 g/mol, F = 96500 C/mol)

Q7. The degree of dissociation of a weak acid is 0.1, and its molar conductivity at infinite dilution is 380 S cm\(^2\) mol\(^{-1}\). What is its molar conductivity at that concentration?

Q8. What is the standard Gibbs energy change for a cell with \( E^\circ_{cell} = 0.59 \, V \) and 1 electron transferred? (F = 96500 C/mol)

Q9. In a fuel cell, the anode reaction produces 0.224 L of H\(_2\)O vapor at STP from H\(_2\). How many coulombs are involved? (F = 96500 C/mol)

Q10. How much charge (in coulombs) is required to oxidize 1 mole of H\(_2\)O to O\(_2\)? (F = 96500 C/mol)