{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

Lecture15_S08 - Feb 22 2008 Lecture 15 Chapter 16 Acids and...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Feb. 22, 2008 Lecture 15, Chapter 16: Acids and Bases Dissolving weak base in pure water only partly ionize H 2 O to give OH - gives basic solution: use K b Base (aq) + H 2 O (l) H(Base) + (aq) + OH- (aq) K b = [H(base) + ][OH - ] [Base] Caffeine is a weak base. A 0.15 M solution has pH = 8.45, find K b caffeine (aq) + H 2 O (l) H(caffeine) + (aq) + OH- (aq) I Find pOH from pH, find [OH - ] eq from pOH pOH = 14-pH = 14.00-8.45 = 5.55; [OH-] eq = 10 -pOH = 10 -5.55 = 2.82x10 -6 0 M 0 M K b = [H(caffeine) + ][OH - ] [caffeine] C E 0.15 M - x (0.15-x) M + x x M + x x M [OH-] eq = 2.82x10 -6 M = [H(caffeine) + ] eq [caffeine] eq = (0.15 – 2.82x10-6)M = 0.15 M K b = [H(caffeine) + ][OH - ] [caffeine] = (2.86x10 -5 ) 2 (0.15) = 5.30x10 -11
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Most remaining questions will ask to find pH of salt solutions This depends on your ability to recognize whether ions in the salt are acids, bases, or spectators Spectator ions do not affect pH : Li + , Na + , K + , Mg 2+ , Ca 2+ , Ba 2+ Cl - , Br - , I - , NO 3 - , ClO 3 - , ClO 4 - , HSO 4 - Ions of strong acids or bases have zero tendency to reform acid or base conjugate acid cations or high oxidation state metals cations Make solutions Acidic : NH 4 + , CH 3 NH 3 + , Al 3+ , Fe 3+ , Cr 3+ Anions, conjugate bases
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}