Electrode Potential — Standard reduction potential, SHE
Electrochemistry
9
JEE Qs
8%
Hard
75
min
Thoroughly understand the sign conventions and the relationship between standard reduction potentials and the relative strengths of oxidizing/reducing agents, as this forms the basis for predicting reaction spontaneity and cell configuration.
🧮 Key Formulas
✅ Key Points for JEE
- 1Electrode potential is the potential difference developed between the electrode and the electrolyte when a metal is placed in a solution of its own ions.
- 2Standard Electrode Potential (E°) is measured under standard conditions: 1 M concentration for ions, 1 atm pressure for gases, and 298 K (25°C) temperature.
- 3The Standard Hydrogen Electrode (SHE) acts as a reference electrode, arbitrarily assigned a standard reduction potential of 0.00 V, against which all other electrode potentials are measured.
- 4IUPAC convention uses Standard Reduction Potential (SRP). A more positive SRP indicates a stronger tendency for reduction (i.e., the species is a stronger oxidizing agent); a more negative SRP indicates a stronger tendency for oxidation (i.e., the species is a stronger reducing agent).
- 5In a galvanic cell, the electrode with the higher (more positive) standard reduction potential will act as the cathode (reduction occurs), and the electrode with the lower (more negative) standard reduction potential will act as the anode (oxidation occurs).
⚠️ Common Mistakes
- ✕Confusing standard oxidation potential with standard reduction potential; always use reduction potentials for consistency (as per IUPAC convention).
- ✕Incorrectly assigning signs when calculating cell potential (E°_cell = E°_cathode - E°_anode). Students might mistakenly add or subtract values without considering the 'reduction at cathode minus reduction at anode' rule.
- ✕Misinterpreting the relative strengths of oxidizing and reducing agents based on the sign and magnitude of standard electrode potentials.
📝 Practice Questions
See allQ54.The element that does not belong to the same period of the remaining elements (modern periodic table) is: 2025 (23 Jan Shift 1) JEE Main Previous Year Paper (1) Iridium (2) Platinum (3) Osmium (4) Palladium
Q67.For the given cell Fe2+ (aq) + Ag+ (aq) →Fe3+(aq) + Ag(s) The standard cell potential of the above reaction is Ag+ + e−→Ag Eθ = xV Given: Fe2+ + 2e−→Fe Eθ = yV Fe3+ + 3e−→Fe Eθ = zV (1) x + y −z (2) x + 2y (3) x + 2y −3z (4) y −2x
Q58.Which of the following electrolyte can be used to obtain H2 S2O8 by the process of electrolysis? (1) Dilute solution of sodium sulphate. (2) Acidified dilute solution of sodium sulphate. (3) Dilute solution of sulphuric acid (4) Concentrated solution of sulphuric acid
Q66.A solution of aluminium chloride is electrolysed for 30 minutes using a current of 2 A . The amount of the aluminium deposited at the cathode is [Given : molar mass of aluminium and chlorine are 27 g mol−1 and 35.5 g mol−1 respectively. Faraday constant = 96500Cmol−1] (1) 1.660 g (2) 0.336 g (3) 0.441 g (4) 1.007 g 2025 (22 Jan Shift 1) JEE Main Previous Year Paper
Q58.Standard electrode potentials for a few half cells are mentioned below : E∘ = 0.34 V, E∘ = −0.76 V Cu2+/Cu Zn2+/Zn Which one of the following cells gives the most negative value of E∘Ag+/Ag = 0.80 V, E∘Mg2+/Mg = −2.37 V ΔG∘ ? (1) Zn Zn2+(1M) Ag+(1M) Ag (2) Zn Zn2+(1M) Mg2+(1M) Mg (3) Ag Ag+(1M) Mg2+(1M) Mg (4) Cu Cu2+(1M)∥Ag+(1M) Ag
Q57. E∘Cr2O2−7 /Cr3+ = 1.33 V E∘Cl2/Cl(−) = 1.36 V Based on the data given below : the strongest reducing agent is : E∘ = 1.51 V E∘ = −0.74 V MnO−4 /Mn2+ Cr3+/Cr (1) Cr (2) Cl− (3) MnO−4 (4) Mn2+
NCERT Chapters
- Class 12 Chemistry Ch 3: Electrochemistry