Today we did the buffer capacity lab. I started with the question: What makes a good buffer? After brainstorming for a bit we went with testing 20mL of buffer by adding small amounts of 1 M HCl and 1 MNaOH (in separate trials) until the pH changed by two. Instructions for lab write-up are on google classroom. Smart board crashed so I do not have notes from today…
Reviewed for test – gave you 6 review problems that took all class to solve. Then pointed out the multiple choice
What is on the test?
1) Definitions (Arrhenius and Bronsted-Lowery/ conjugate pairs)
2) Strong vs. Weak (memorize strong acids and bases, definitions of strong/weak, acid/base dissociation constants (Ka, Kb), molecular level pictures, rate of reaction)
3) pH calculations (strong vs weak, relationship with Kw and water ionization (dissociation), ice table, allowed assumption so you don’t have to use quadratic)
4) Salt hydrolysis (relative strength of conjugates, determine if solution will be acidic, neutral or basic, write hydrolysis reactions, identify spectator ions, calculate pH, Kw = Ka*Kb)
5) Buffers (weak a/b + conjugate in relatively significant proportion, can use henderson-hasselbach equation to solve for pH, recognize buffer solutions (including 1/2 titration method), explain how a buffer works, molecular level picture)
6) Titration (explain (relate to salt hydrolysis) and solve for equivalence point, how to get Ka from titration curve, what indicator to use given pKa, end point vs equivalence point, buffering region, molecular level pictures)
Sample questions from today’s review session.
Today we started with the Atomic Emission lab from first year chem b/c we skipped it last year so many of you hadn’t learned anything about it! You measured the wavelengths of all 5 atoms and we briefly talked about why the atoms were different. Here’s a video if you missed it.
Work on Bohr Model lab. Turn in by Tuesday morning.