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In class notes for November 28, 2007

# In class notes for November 28, 2007 - -o Plug into weak...

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General Chemistry Lecture 102a In class notes for November 28, 2007 Regrade requests for Exam #3 are due on Monday. Last lecture o Buffers Today o Buffers and CO 2 worksheet Summary of what to do with buffers Add acid or base to existing buffer (HA and A - mixture) o Calculate new amounts Calculate original moles of added acid or base and weak acid (HA) and weak base (A - ) Neutralize added acid or base with buffer HA + OH - → A - + H 2 O A - + H 3 O + → HA + H 2 O Calculate new amounts of HA and A - Convert to new concentrations of HA and A
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Unformatted text preview: -o Plug into weak acid equilibrium to get new pH HA + H 2 O ⇌ A-+ H 3 O + += [ ][ -] H3O Ka HA A =- [ ][ -] pH pKa log HA A • Now we will do an example and add hydroxide to the buffer system. • SEE A • Buffer design o Large amount of HA and A-relative to added H 3 O + or OH-o Ratio should be within 0.2 to 4 ([HA]/[A-]) original o Approximately equal amounts of HA and A-o Pick weak acid so that pH desired is about pKa of acid...
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