Consider the Following Three Buffer Reactions

Short Answer

Consider the following three buffer reactions.
Buffer 1: protein-H⁺ and protein
Buffer 2: H₂CO₃ and HCO₃^-
Buffer 3: H₂PO₄^- and HPO₄^2-
Fill in the blank with the appropriate integer (1,2,or 3)to indicate the buffer system described.
-Buffer______________________can have a variable pK_a value.