TABLE 16.3 Acid-Dissociation Constants of Some Common Polyprotic Acids Name Formula K1 K2 Ascorbic H2CH¿O6 8.0 x 10-5 1.6 x 10-12 Carbonic Н.СО, 4.3 x 10-7 5.6 x 10-1" Citric H;C,H5O7 7.4 x 104 1.7 x 10-5 4.0 x 107 Охalic HOOC-COOH 5.9 x 10-2 6.4 x 10-5 Phosphoric Н,РО, 7.5 x 10-3 6.2 x 10-8 4.2 x 10-13 Sulfurous H,SO, 1.7 x 10 2 6.4 x 108 Sulfuric H2SO4 Large 1.2 x 10-2 Tartaric С-Н.О,(СООН)2 1.0 x 10- 4.6 x 10-5

Citric acid, which is present in citrus fruits, is a triprotic acid
. (a) Calculate the pH of a 0.040 M solution of
citric acid. (b) Did you have to make any approximations
or assumptions in completing your calculations? (c) Is the
concentration of citrate ion (C₆H₅O₇^3-) equal to, less than,
or greater than the H⁺ ion concentration?