Question 6 The solution of equilibrium problems is essential in the analysis of many weak acid-base systems in surface water and in water treatment. a. Write the mass balance, proton balance and equilibrium relationships for a 0.2M Na2CO3 solution in water. (8) b. Using a spreadsheet, calculate the concentrations of the different carbonate species at different pH-values and draw a pC-pH diagram for the system and show the equivalence point of the solution on the diagram. (12) NB. Please submit your spreadsheets electronically on clickUP. c. Using simplifying assumptions, calculate the equilibrium pH of a solution made by adding acetic acid to water to give a concentration of 1.5102M at 25C. Ignore activity corrections. (8) d. Oxalic acid ( HOOCCOOH) is a diprotic acid with pKAI=1.25 and pKA2=4.28. Using a spreadsheet, determine the equilibrium pH of a solition made by adding enough oxalic acid to water to give a concentration of 102M (5) e. Complete the following table by giving the effect of the addition of X moles/ /h the particular chemical on the parameter as indicated in a closed system. Show 0 for no effect, +X (or 2X ) for increase of X (or 2X ) mole/l and - X (or 2X ) for decrease of X (or 2X) mole/l (6)