Electrolysis and Faraday's laws — NEET & JEE Questions

Question 1 · difficulty L1 · recall

According to Faraday's first law of electrolysis, the mass of a substance deposited at an electrode is directly proportional to which quantity?

• A. The charge passed through the electrolyte
• B. The resistance of the electrolyte
• C. The electrode area only
• D. The distance between the electrodes only

Question 2 · difficulty L2 · understanding

One faraday of electric charge deposits one gram-equivalent of a substance during electrolysis. Approximately how much charge is one faraday?

• A. $9.65\times10^2\,\text{C}$
• B. $9.65\times10^3\,\text{C}$
• C. $9.65\times10^4\,\text{C}$
• D. $9.65\times10^5\,\text{C}$

Question 3 · difficulty L2 · understanding

During electrolysis of molten sodium chloride, which species is reduced at the cathode?

• A. $\text{Na}^+$
• B. $\text{Cl}^-$
• C. $\text{Na}$
• D. $\text{Cl}_2$

Question 4 · difficulty L2 · understanding

The same quantity of electricity is passed through solutions of $\text{AgNO}_3$ and $\text{CuSO}_4$. Which statement correctly compares the moles of Ag and Cu deposited, assuming $\text{Ag}^+$ and $\text{Cu}^{2+}$ are discharged?

• A. Equal moles of Ag and Cu are deposited
• B. Moles of Ag deposited are twice the moles of Cu deposited
• C. Moles of Cu deposited are twice the moles of Ag deposited
• D. Four times as many moles of Ag as Cu are deposited

Question 5 · difficulty L3 · application

A current of $2.0\,\text{A}$ is passed through a silver nitrate solution for $965\,\text{s}$. What mass of silver is deposited? Take $F=96500\,\text{C mol}^{-1}$ and molar mass of Ag $=108\,\text{g mol}^{-1}$.

• A. $1.08\,\text{g}$
• B. $2.16\,\text{g}$
• C. $10.8\,\text{g}$
• D. $21.6\,\text{g}$

Question 6 · difficulty L3 · application

How long must a current of $5.0\,\text{A}$ pass through a $\text{CuSO}_4$ solution to deposit $3.175\,\text{g}$ of copper? Take $F=96500\,\text{C mol}^{-1}$ and molar mass of Cu $=63.5\,\text{g mol}^{-1}$.

• A. $965\,\text{s}$
• B. $1930\,\text{s}$
• C. $3860\,\text{s}$
• D. $7720\,\text{s}$

Question 7 · difficulty L3 · application

A charge of $9650\,\text{C}$ is passed through molten $\text{AlCl}_3$. What mass of aluminium is produced? Take $F=96500\,\text{C mol}^{-1}$ and molar mass of Al $=27\,\text{g mol}^{-1}$.

• A. $0.9\,\text{g}$
• B. $2.7\,\text{g}$
• C. $9.0\,\text{g}$
• D. $27.0\,\text{g}$

Question 8 · difficulty L3 · application

Two electrolytic cells containing $\text{AgNO}_3$ and $\text{CuSO}_4$ are connected in series. If $10.8\,\text{g}$ of Ag is deposited in the first cell, what mass of Cu is deposited in the second? Take molar masses Ag $=108\,\text{g mol}^{-1}$ and Cu $=63.5\,\text{g mol}^{-1}$.

• A. $1.5875\,\text{g}$
• B. $3.175\,\text{g}$
• C. $6.35\,\text{g}$
• D. $12.70\,\text{g}$

Question 9 · difficulty L4 · application

A current of $4.0\,\text{A}$ is passed for $2412.5\,\text{s}$ through an aqueous $\text{CuSO}_4$ solution using inert electrodes. What volume of oxygen at STP is liberated at the anode? Take $F=96500\,\text{C mol}^{-1}$ and molar volume at STP $=22.4\,\text{L mol}^{-1}$.

• A. $0.28\,\text{L}$
• B. $0.56\,\text{L}$
• C. $1.12\,\text{L}$
• D. $2.24\,\text{L}$

Question 10 · difficulty L4 · application

A copper voltameter and a silver voltameter are connected in series. After electrolysis, the increase in mass of the silver cathode is $5.40\,\text{g}$. What is the increase in mass of the copper cathode? Take molar masses Ag $=108\,\text{g mol}^{-1}$ and Cu $=63.5\,\text{g mol}^{-1}$.

• A. $0.794\,\text{g}$
• B. $1.588\,\text{g}$
• C. $3.175\,\text{g}$
• D. $6.350\,\text{g}$