Question

1. What is half cell reaction (both left and right) and the net cell reaction from the following line notation?

Pt(s) | UO 2 2+(0.050 M) , U4+(0.050 M), HCO2H(0.10 M), HCO2Na(0.30 M) || Fe3+(0.050 M), Fe2+(0.025 M) | Pt(s)

2. How a pH works? and the reason why the junction potential at the outer surface of the ion selective membrane depends on pH?

Answer 1

1 ) Left reaction ,

UO²⁺ + HCOOH ----------> UO4⁺ + 2e^- + CO₂

Right reaction,

Fe ³⁺ + 1 e^- -----------> Fe ²⁺

Net cell reaction,

  

UO²⁺ + HCOOH ----------> UO4⁺ + 2e^- + CO₂

Fe ³⁺ + 1 e^- -----------> Fe ²⁺

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   UO²⁺ + HCOOH +    Fe ³⁺ + 1 e^- ---------> UO4⁺ + 2e^- + CO₂ + Fe ²⁺

2 ) Many electron-transfer reactions involve hydrogen ions and hydroxide ions. The standard potentials for these reactions therefore refer to the pH, either 0 or 14, at which the appropriate ion has unit activity. Because multiple numbers of H⁺ or OH^– ions are often involved, the potentials can vary greatly with the pH.