01:160:162 Lecture Notes - Lecture 18: Buffer Solution, Conjugate Acid, Weak Base
18 Nov 2016
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C2h3o2- ions) (a) common ion effect- solution contains two substances (hc2h3o2 and nac2h3o2) that share a common ion (c2h3o2-) 0. 100+x: ka=[h3o+][c2h3o-]/[hc2h3o2] x(0. 100+x)/0. 100-x x=1. 8*10^-5 [h3o+]=x=1. 8*10^-5 m ph=-log[h3o+]=- log(1. 8*10^-5) 4. 74, the henderson-hasselbalch equation, consider a buffer containing the generic weak acid ha and its conjugate base a-. Ka by the ratio of the concentrations of the acid and the conjugate base (a) [h3o+]=ka[hc2h3o2]/[c2h3o2-]=ka. 0. 125 mol (1) neutralizing 0. 025 mol of the strong acid (h+) requires. 0. 025 mol of the weak base (a-) so a- decreases by 0. 025 mol and ha increases by 0. 025 mol (1:1:1 stoichiometry of the neutralization reaction: the equilibrium calculation, ha(aq)+h2o(l) h3o(+)(aq)+a-(aq) 0. 125/0. 075 ph=-log[h3o+] (1) since the expression for x contains a ratio of concentrations. [ha]/[a-] we can substitute the amounts of acids and base in moles in place of concentration because in a single buffer solution, the volume is the same for both the acid and the base (a) volumes cancel: (i)
