Lect+23+08 - Lecture 23 Goals Examples for calculating...

Info iconThis preview shows pages 1–6. Sign up to view the full content.

View Full Document Right Arrow Icon
Lecture 23 Goals Examples for calculating concentrations and pH of weak acid solutions You will have a plain language understanding of buffers and the species that control buffering. Examples for calculating concentrations and pH of buffers and stressed buffer solutions You will have a conceptual understanding of Acid Base Titration curves and be able to figure out the primary species during titration Calculating the response of pH to titration You will have a plain language understanding of polyprotic acids and their neutralization
Background image of page 1

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

View Full DocumentRight Arrow Icon
Hydrolysis 4 + 3
Background image of page 2
Weak Base Hydrolysis Prob. 10.38 The pH = 11.5 at 298 K of an aqueous solution of Na(CN) WHAT IS THE [CN - ] CONCENTRATION? Is HCN a weak Acid? CN - (aq) + H 2 O(l) HCN(aq) + OH - (aq) K a = 6.17 x 10 -10 and K a K b =10 -14 so K b = 1.6 x 10 -5 K b = [OH - ][HCN]/[CN - ] But [CN - ]= [OH - ] because weak base pOH = 2.50 since pH + pOH =14 and pH = 11.5 So [OH - ] = 10 -2.5 = 3.2 x 10 -3 = [HCN] [CN - ] = ([OH - ][HCN]/ K b )= 0.62M
Background image of page 3

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

View Full DocumentRight Arrow Icon
Buffers A buffer is a solution which maintains a relatively constant pH despite small additions of acid or base. HA(aq) + H 2 O(l) H 3 O + (aq) + A - (aq) If we add both HA and A - to the solution then there is chemical resistance to pH change when we add either acid or base. The equilibrium damps the effect of adding acid or base [ H 3 O + ]= K a ([HA]/[A - ]) and if both HA and A - are large then the [ H 3 O + ] is buffered Many physiological systems are buffered
Background image of page 4
Calculations with buffers Calculations are similar to the equilibrium calculations in chapter 14 where both
Background image of page 5

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

View Full DocumentRight Arrow Icon
Image of page 6
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 04/01/2008 for the course CHEM 230 taught by Professor Sharp during the Winter '08 term at University of Michigan.

Page1 / 17

Lect+23+08 - Lecture 23 Goals Examples for calculating...

This preview shows document pages 1 - 6. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online