Redox Equilibria I 2020

1. Calculate pe values for the following equilibrium conditions (assuming 25^o C):
   1. An acid solution 10^-6 M in Fe³⁺ and 10^-3 M in Fe²⁺.
   2. A natural water at pH 7.5 in equilibrium with the atmosphere.
   3. A natural water at pH 8 containing 10^-5 M Mn²⁺ in equilibrium with MnO₂(s).
   4. A natural water at pH 7 containing 10^-4 M HS^– and 10^-6 M SO₄^2-.
   5. Different metals are sometimes connected together in household faucets. Determine whether Zn or Ni will dissolve when each are connected together in a galvanic cell at standard conditions.
2. Pure silver (Ag(s)) is placed in two waters; one is surface water in equilibrium with the atmospshere and the other is a groundwater under sulfate reducing conditions (SO₄^2- M and HS^– M). Both water are at pH 7.0.
   1. What will be the concentration of Ag⁺ at equilibrium in both waters?
   2. What volume of water would be required to dissolve 1 mg of silver in both water?