The pH of natural waters falls in the range of 5 - 8.5, with some exceptions. Most surface waters are dominated by the carbonate system so that H2CO3 (pKa = 6.35) and HCO3- (pKa = 10.33) are the principal acids. At pH's of 5.35, 6.35, and 7.35, calculate the ratio H2CO3 / HCO3- in the water. Ignore differences between activity and concentration.