NEET Electrochemistry — Set 7

Question 1

What is the emf of the cell $ Sn(s) | Sn^{2+}(0.05 \, M) || H^+(0.1 \, M) | H_2(g)(1 \, bar) | Pt(s) $ at 298 K? (Given: $ E^\circ_{Sn^{2+}/Sn} = -0.14 \, V $, $ E^\circ_{H^+/H_2} = 0.00 \, V $)

Accepted Answer

$ E^\circ_{cell} = 0.00 - (-0.14) = 0.14 \, V $. $ E_{cell} = 0.14 - \frac{0.059}{2} \log \frac{0.05}{0.1^2} = 0.14 + 0.039 = 0.179 \, V $.

Question 2

A conductivity cell with a 0.015 M KNO$_3$ solution has a resistance of 300 Ω and a cell constant of 0.75 cm$^{-1}$. What is the molar conductivity?

Accepted Answer

$ \kappa = \frac{\text{cell constant}}{R} = \frac{0.75}{300} = 0.0025 \, S \, cm^{-1} $. $ \Lambda_m = \frac{\kappa \times 1000}{c} = \frac{0.0025 \times 1000}{0.015} = 166.67 \, S \, cm^2 \, mol^{-1} $.

Question 3

A cell $ Cd(s) | Cd^{2+}(0.005 \, M) || Br_2(l) | Br^-(0.01 \, M) | Pt(s) $ operates at 298 K. What is the cell potential? (Given: $ E^\circ_{Cd^{2+}/Cd} = -0.40 \, V $, $ E^\circ_{Br_2/Br^-} = 1.07 \, V $)

Accepted Answer

$ E^\circ_{cell} = 1.07 - (-0.40) = 1.47 \, V $. $ E_{cell} = 1.47 - \frac{0.059}{2} \log \frac{[Cd^{2+}][Br^-]^2}{1} = 1.47 - 0.0295 \log (0.005 \times 0.0001) = 1.47 + 0.103 = 1.573 \, V $.

NEET Chemistry: Electrochemistry — Practice Set 7

Q1. What is the emf of the cell \( Sn(s) | Sn^{2+}(0.05 \, M) || H^+(0.1 \, M) | H_2(g)(1 \, bar) | Pt(s) \) at 298 K? (Given: \( E^\circ_{Sn^{2+}/Sn} = -0.14 \, V \), \( E^\circ_{H^+/H_2} = 0.00 \, V \))

Q2. A conductivity cell with a 0.015 M KNO\(_3\) solution has a resistance of 300 Ω and a cell constant of 0.75 cm\(^{-1}\). What is the molar conductivity?

Q3. A cell \( Cd(s) | Cd^{2+}(0.005 \, M) || Br_2(l) | Br^-(0.01 \, M) | Pt(s) \) operates at 298 K. What is the cell potential? (Given: \( E^\circ_{Cd^{2+}/Cd} = -0.40 \, V \), \( E^\circ_{Br_2/Br^-} = 1.07 \, V \))

Q4. What is the emf of the cell \( Co(s) | Co^{2+}(0.02 \, M) || H^+(0.01 \, M) | H_2(g)(1 \, bar) | Pt(s) \) at 298 K? (Given: \( E^\circ_{Co^{2+}/Co} = -0.28 \, V \), \( E^\circ_{H^+/H_2} = 0.00 \, V \))

Q5. A cell has \( E^\circ_{cell} = 0.52 \, V \) and an equilibrium constant of \( 10^{17} \) at 298 K. How many electrons are transferred?

Q6. How many Faradays are required to deposit 1.62 g of silver from AgNO\(_3\) solution? (Atomic mass of Ag = 108 g/mol)

Q7. In a fuel cell, what is the electrolyte commonly used?

Q8. During electrolysis of aqueous K\(_2\)SO\(_4\) with inert electrodes, 0.336 L of gas (STP) is collected at both electrodes. How many coulombs were passed? (F = 96500 C/mol)

Q9. What is the time (in seconds) required to deposit 0.585 g of chromium from a Cr\(_2\)(SO\(_4\))\(_3\) solution using a current of 0.5 A? (Atomic mass of Cr = 52 g/mol, F = 96500 C/mol)

Q10. How many electrons are involved in the reduction of 1 mole of \( SO_4^{2-} \) to \( S \) in acidic medium?