Iron concentration given pH and pE values

At pH 6.00 and pE 2.90, what is the concentration of Fe2+ (mol/L) in equilibrium with Fe(OH)3?

radioactive waste

I would like some information as to the pros and cons of radioactive waste. I would like more info on the pros of using nuclear energy to meet our high-energy demands even though there is readioactive waste. How we dispose of it and the safety of the way we dispose of it.

pH and pE are given, need concentration of Fe2+

At pH 6.00 and pE 2.70, what is the concentration of Fe2+ (mol/L) in equilibrium with Fe(OH)3?

given temp, Eh(??) and pH, find disolved amt of Oxygen (ppm)

A ground water sample , at 25 C, has Eh= 0.6 and pH=6.40. Assuming the system is at equilibrium, calculate the amount of dissolved oxygen (ppm) in the groundwater sample.

pH is given, need calcium carbonate dissolved per liter

The average pH of precipitation in rural areas is 5.50. Assuming that the pH is controlled by the carbonate system, i.e., no anthropogenic acid gases are present in the atmosphere, calculate the amount of calcium carbonate (mg) dissolved per liter of rainwater. pKa1=6.33, KCO2=3.388e-02 Hint: PCO2=3.16E-4, I'm confused!