Normal or Standard Hydrogen Electrode Chemistry Notes
Normal or Standard Hydrogen Electrode (NHE or SHE)
→ Standard hydrogen electrode has plantinum electrode coated with platinum black. It is surrounded by glass tube and platinum electrode is dipped in acidic solution In this, hydrogen gas is passed at 1 atmospheric pressure whose path is above from glass tube. Here, a passage is present towards above in glass tube from where residual hydrogen gas is evolved.
→ The molar concentration of acidic solution is 1 Mand HCl solution is taken. When hydrogen gas is passed through solution then some amount of gas is adsorbed at the surface of platinum, Remaining gas is soluble in molar solution of acid. Due to this reason, an equilibrium is established between adsorbed hydrogen gas and hydrogen ions present in solution at platinum electrode. Hydrogen acts as cathode and anode. When it acts as anode then oxidation takes place on it.
→ The value of electrode potential of standard hydrogen electrode at 298 K is considered as zero. For determining electrode potential of other electrode, it is added with it and we measure e.m.f. of cell. This e.m.f. represents electrode potential of other cell. This electrode potential is standard electrode potential because it determines in standard state. Standard state is 298 K temperature, 1 atmospheric pressure and 1 M concentration.