CHEM 112 Lecture Notes - Lecture 2: Deprotonation, Quadratic Equation, Hydrogen Bond
Document Summary
Polyprotic aid: compound which can donate more than one proton. The titrations of polyprotic acids with a strong base are similar to that of a monoprotic acid, except that there are additional stoichiometric points associated with the addition acidic hydrogens. Pka values are horizontal slopes on ph vs volume graphs. In the middle of the buffer zone, ph=pka. Vertical slopes are stoichiometric point for equilivance points. The hydrogen bonding between carboxylates oxygen and the hydrogen on the hydroxyl group stabalize this species towards dissociation of the proton. H2 so4 (aq) + h2o(l) hso4 - (aq) + h3o+ (aq) The conjugate base, hso4 - , is a weak acid (pka = 1. 92), such that the second equilibrium involving deprotonation of hso4 - , also contributes to the concentration of h3o+ . Hso4 - (aq) + h2o(l) so4 2- (aq) + h3o+ (aq) We can solve for x using the quadratic equation, and find that x = 4. 3 x 10-3 .
