Assume the pe of the surface water of a lake is controlled by the O,/H,O half-reaction. What would the concentration of ferrous iron (Fe2") be in the system if it has a pH of 8 and it is in equilibrium with the atmosphere (Po2 = 0.21 atm)? Assume the temperature is 25 °C. log K pe O2(g) + 4H* + 4e = 2H2O 83.1 20.78 FEOOH(s) + 3H* + e = Fe2* + 2H20 13.5 13.50

Each row of the table below describes an aqueous solution at 25 °C. The second column of the table shows the initial components of the solution. • Use the checkboxes in the third column to explain the type of the initial solution. The fourth column describes a change in the solution. • Use the fifth column to predict how the change in the solution will change its pH. solution initial components A B C D H₂O H₂O, NaOH H₂O H₂O, NaOH initial type (check all that apply) acidic basic neutral acidic basic neutral acidic basic neutral acidic basic оо 00 neutral change add HCl add Na Br add K Cl add H Br effect of change on pH (check one) pH higher pH lower ο ο1ο ο ο ο ο ο pH the same pH higher pH lower pH the same pH higher pH lower pH the same pH higher pH lower pH the same

Consider the reaction below. Co(H,O),* (aq) + 4 Cl¯ (aq) = COC1," (aq) + 6 H,O (1I) The equilibrium constant expression (K) of the reaction does not include the concentration of H,O even though the reaction produces six moles of water. Explain.