Question

The groundwater sample was analysed. The measured pH of the test water at 25°C had a value, pH = 3.8. The concentration of Zn2+ ions in water was also determined to be 4.132·10-2 mol/L.

Groundwater is in equilibrium with sediment containing MnO2 and ammonia. Calculate the

concentration of NH4+ ions under these conditions.

Standard reduction electrode potentials for reactions:

Zn 2++ 2e →Zn E°= -0.76V

 2MnO 2 + 2NH4+ 2e → Mn2O3 +2NH3+ H2O

 E°= 0.74 V

Write a sum cell reaction.

Answer 1

The sum cell reaction and potential of the cell can be calculated by Nerst equation.