Piperazine is a diprotic weak base used as a corrosion inhibitor and an insecticide. Its ionization is described by the following equations.

The piperazine used commercially is a hexahydrate, C₄H₁₀N₂ · 6H₂O. A 1.00-g sample of this hexahydrate is dissolved in 100.0 mL of water and titrated with 0.500 M HCl. Sketch a titration curve for this titration, indicating 

(a) The initial pH; 

(b) The pH at the halfneutralization point of the first neutralization; 

(c) The volume of HCl(aq) required to reach the first equivalence point; 

(d) The pH at the first equivalence point;

(e) The pH at the point at which the second step of the neutralization is half-completed; 

(f) The volume of 0.500 M HCl(aq) required to reach the second equivalence point of the titration; 

(g) The pH at the second equivalence point.

Transcribed Image Text:

HN(C₂H8) NH + H₂O = [HN(C4H8) NH₂]+ + OH [HN(C4H8) NH₂] + H₂O = [H₂N(C4H8) NH₂]²+ + OH pKb₁ pKb₂ = 8.67 = 4.22