18. Tris is the basic form of a common biological buffer. What volume of 0.100 M HBr would have to be added to a 125 mL solution of 0.0250 M Tris to make a buffer with pH 7.5? (Hint: Work in moles, not final concentrations.) Data: Ka(TrisH) 8.51 10-9 = A) 23.0 mL B) 62.0 mL C) 60.4 mL D) 24.6 mL E) 28.2 mL