The pH in a lake the size of 4.0 km X 7.0 km and an average depth of 100 m is found to be 4.5. Calculate the mass of calcium carbonate that must be added to the lake water in order to raise its pH to 6.0, assuming the reaction of H+ with CaCO3 gives CO2 here (answer in grams).
Hint: Calculate volume of lake, change of H+ concentration, mol of calcium carbonate required.