Phosphoric acid (H₃PO₄) is a triprotic acid; pKa1 = 2.12, pKa2 = 7.21, pKa3 = 12.32. What does the value of pKa signify in this con?
a) Concentration of the acid
b) Temperature sensitivity of the acid
c) Strength of the acid's dissociation
d) Rate of reaction of the acid