Which of the following statement(s) differentiate between electrochemical cell and electrolytic cell — Electrochemistry Chemistry Question

💡 Solution & Explanation

Step 1 - Define the Operational Principles of both Cells To understand how to differentiate between the two systems, we must analyze their fundamental thermodynamic and operational definitions: * **Electrochemical Cell (Galvanic/Voltaic Cell):** A device that converts chemical energy released during a spontaneous chemical reaction into electrical energy. * **Electrolytic Cell:** A device that utilizes external electrical energy to drive a thermodynamically non-spontaneous chemical reaction. Step 2 - Analyze Option (A): Spontaneous or non-spontaneous nature of the chemical process The thermodynamic feasibility of reactions within both cells is defined as: * In an electrochemical cell, the cell reaction proceeds spontaneously in the forward direction. The Gibbs free energy change ($\Delta G$) is negative, and the actual cell potential ($E_{\ce{cell}}$) is positive: $$\Delta G < 0 \quad \text{and} \quad E_{\ce{cell}} > 0$$ * In an electrolytic cell, the chemical reaction is non-spontaneous. It requires external electrical work to be forced through the system. The thermodynamic criteria are: $$\Delta G > 0 \quad \text{and} \quad E_{\ce{cell}} < 0$$ Since spontaneity vs. non-spontaneity is a fundamental difference, **Option (A) successfully differentiates** between the two cells. Step 3 - Analyze Option (B): Chemical reactions occurring at the electrodes The IUPAC definition of electrodes in any electrochemical system is strictly based on the specific type of chemical reaction taking place on their surfaces: * **Anode:** The electrode where **oxidation** (loss of electrons) occurs: $$\ce{Red -> Ox + n e^-}$$ * **Cathode:** The electrode where **reduction** (gain of electrons) occurs: $$\ce{Ox + n e^- -> Red}$$ Because oxidation universally occurs at the anode and reduction universally occurs at the cathode in both cell types, the basic nature of electrode chemistry **does not differentiate** between an electrochemical cell and an electrolytic cell. Thus, **Option (B) is incorrect**. Step 4 - Analyze Option (C): Positive and negative nature of anode The electrical charge (polarity) of the electrodes is determined by the source of electrons: * **Electrochemical Cell:** The anode is the site of spontaneous oxidation, which continuously releases electrons onto the electrode's surface. This accumulation of negative charge makes the anode the **negative terminal ($-$)**. * **Electrolytic Cell:** To force non-spontaneous oxidation, the anode must be connected to the positive terminal of an external DC power source (which pulls electrons away from the species). Thus, the anode is the **positive terminal ($+$)**. Since the anode is negative in an electrochemical cell and positive in an electrolytic cell, the polarity of the anode **successfully differentiates** between the two types of cells. Thus, **Option (C) is correct**. Step 5 - Analyze Option (D): Dependence on Faraday's law Faraday's laws of electrolysis relate the mass ($w$) of a substance deposited or liberated at an electrode to the total quantity of electric charge ($Q$) passed through the electrolyte: $$w = Z \cdot I \cdot t$$ These laws are derived from the fundamental principles of the conservation of charge and stoichiometry of redox reactions. Consequently, Faraday's laws apply universally to any redox process occurring at an electrode interface under an electric current, regardless of whether the cell operates spontaneously as a galvanic cell or is driven externally as an electrolytic cell. Since both cell types obey Faraday's laws, this dependence **does not differentiate** between them. Thus, **Option (D) is incorrect**. $$\text{Correct Options: } \boxed{\text{A, C}}$$