Question

1. Consider the following half-cell redox reaction involving NO3^- at a concentration of 10^-5M (mol/L) and ammonium at a concentration of 10^-3 M in groundwater with a pH of 8. What is the Eh of the system at 25 degrees Celsius?

1/8NO3^- + 5/4H^+ +e^- ↔ 1/8 NH^4+ +3/8H2O

Thermodynamic data Delta Gf (KJ/mol)

Al^3+ -485.0

Ni^2+ -45.6

NH4^+ -79.31

NO3^- -108.74

SO4^2- -177.75

HS^- 2.93

H2O -237.129