Consider the titration of 25 mL of 0.0500 M Sn2 with 0.100 M Fe3 in 1 M HCl to give Fe2 and Sn4 , using Pt indicator electrode and saturated calomel electrode (SCE) . The titration reaction: Sn to the power of 2 plus end exponent plus 2 Fe to the power of 3 plus end exponent space rightwards harpoon over leftwards harpoon space Sn to the power of 4 plus end exponent space plus space 2 Fe to the power of 2 plus end exponent Half-reactions for the indicator electrode: Fe to the power of 3 plus end exponent space plus space straight e to the power of minus space rightwards harpoon over leftwards harpoon space Fe to the power of 2 plus end exponent E to the power of ring operator space equals space 0.732 space straight V Sn to the power of 4 plus end exponent plus 2 straight e to the power of minus space rightwards harpoon over leftwards harpoon space Sn to the power of 2 plus end exponent E to the power of ring operator space equals space 0.139 space straight V SCE electrode potential ESCE