NEET Electrochemistry — Set 6

Question 1

During the electrolysis of aqueous CuSO$_4$ using copper electrodes, what mass of copper is deposited at the cathode if a current of 1 A flows for 965 seconds? (Faraday constant = 96500 C/mol, Atomic mass of Cu = 63.5 g/mol)

Accepted Answer

Charge $ Q = I \times t = 1 \times 965 = 965 \, C $. For $ Cu^{2+} + 2e^- \rightarrow Cu $, 2F (193000 C) deposits 63.5 g Cu. Mass = $ \frac{63.5 \times 965}{2 \times 96500} = 0.3175 \, g $.

Question 2

The degree of dissociation of a weak electrolyte is 0.25, and its molar conductivity is 95 S cm$^2$ mol$^{-1}$. What is its $ \Lambda_m^\circ $?

Accepted Answer

$ \alpha = \frac{\Lambda_m}{\Lambda_m^\circ} $, $ 0.25 = \frac{95}{\Lambda_m^\circ} $, $ \Lambda_m^\circ = 380 \, S \, cm^2 \, mol^{-1} $.

Question 3

A cell $ Co(s) | Co^{2+}(0.01 \, M) || Br_2(l) | Br^-(0.05 \, M) | Pt(s) $ operates at 298 K. What is the cell potential? (Given: $ E^\circ_{Co^{2+}/Co} = -0.28 \, V $, $ E^\circ_{Br_2/Br^-} = 1.07 \, V $)

Accepted Answer

$ E^\circ_{cell} = 1.07 - (-0.28) = 1.35 \, V $. $ E_{cell} = 1.35 - \frac{0.059}{2} \log \frac{[Co^{2+}][Br^-]^2}{1} = 1.35 - 0.0295 \log (0.01 \times 0.0025) = 1.35 + 0.073 = 1.423 \, V $.

NEET Chemistry: Electrochemistry — Practice Set 6

Q1. During the electrolysis of aqueous CuSO\(_4\) using copper electrodes, what mass of copper is deposited at the cathode if a current of 1 A flows for 965 seconds? (Faraday constant = 96500 C/mol, Atomic mass of Cu = 63.5 g/mol)

Q2. The degree of dissociation of a weak electrolyte is 0.25, and its molar conductivity is 95 S cm\(^2\) mol\(^{-1}\). What is its \( \Lambda_m^\circ \)?

Q3. A cell \( Co(s) | Co^{2+}(0.01 \, M) || Br_2(l) | Br^-(0.05 \, M) | Pt(s) \) operates at 298 K. What is the cell potential? (Given: \( E^\circ_{Co^{2+}/Co} = -0.28 \, V \), \( E^\circ_{Br_2/Br^-} = 1.07 \, V \))

Q4. What is the time (in seconds) required to deposit 0.355 g of cobalt from a CoSO\(_4\) solution using a current of 0.2 A? (Atomic mass of Co = 59 g/mol, F = 96500 C/mol)

Q5. What is the emf of the cell \( Cr(s) | Cr^{3+}(0.002 \, M) || Ag^+(0.05 \, M) | Ag(s) \) at 298 K? (Given: \( E^\circ_{Cr^{3+}/Cr} = -0.74 \, V \), \( E^\circ_{Ag^+/Ag} = 0.80 \, V \))

Q6. How many coulombs are required to deposit 6.75 g of potassium from a KCl solution? (Atomic mass of K = 39 g/mol, F = 96500 C/mol)

Q7. A cell reaction has \( \Delta_r G^\circ = -285900 \, J/mol \) and involves 3 electrons at 298 K. What is the standard emf? (F = 96500 C/mol)

Q8. During electrolysis of aqueous NaBr with inert electrodes, 0.112 L of Br\(_2\) gas (STP) is produced at the anode. How many coulombs were passed? (F = 96500 C/mol)

Q9. A cell reaction has \( E^\circ_{cell} = 1.36 \, V \) and an equilibrium constant of \( 10^{46} \) at 298 K. How many electrons are transferred?

Q10. In electrolysis, 0.635 g of Cu (atomic mass 63.5 g/mol) is deposited from CuSO\(_4\) using 0.5 A for 3860 s. What is the percentage efficiency of the process? (F = 96500 C/mol)