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CH. 17 - Coggle Diagram
CH. 17
Buffers!
In order to resist changes in pH, buffers must have an acid and a base that don't consume each other- weak ones!
Buffer doesn't mean perfect proportion of acid and base, and in that case, you must calculate pH based off of these proportions (whichever way you want.)
calculating pH: use Ka, or HH equation:
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BUFFER CAPACITY: ultimately, the more moles of the buffering component, the more it can "soak up!" Which almost always means a HIGHER CONCENTRATION leads to higher buffer capacity.
pH range: principle is that when concentrations of acid/base buffer components are the SAME is when it works best. And it only works when they do not exceed the other by a factor of 10. MEANING: pH = pKa for ideal buffer, and within +/- 1 of pH (log(10) or log(1/10)) will still work.
TITRATIONS:
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STEP 3: at least in concept, figure out what point of titration you end up at, then proceed with calculations accordingly
- 0 titrant: do basic Ka/H+ calculation.
- Some titrant: use ICE table to get final equations
- Equivalence: if strong/strong, just 7. If weak/strong, all original weak will be the conjugate and probably have to convert Ka/Kb to its inverse to do equilibrium calc. w/just conjugate conc.
- Past equivalence point: all of beaker acid/base will be used up, and excess titrant will be used to calculate pH. Any weak components NEGLIGIBLE compared to excess titrant.
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STEP 1: Figure out if either strong w/strong, or weak w/strong.
BUILDING ON:
Remember that we are STILL talking about acid-base, therefore reversible, therefore equilibrium-tending reactions.
ECEs still work in the same way, but a key is to remember La Chat's as well. With it in mind, it makes sense that existing ion concentration would affect further dissociation.
For the most part, ALL PROBLEMS HERE WILL JUST BE EQUILIBRIUM REACTIONS THAT MAY OR MAY NOT HAVE PREEXISTING IONS (that are easily accounted for, mathematically speaking.)
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