Week 6 Notes

When would you consider the autoionization of water?

when pH is 6-8

when does dissolving salts result in a neutral solution?

when salts have a strong acid and strong base

when does dissolving salts result in a basic solution?

when salts have a strong base and/or weak acid

when does dissolving salts result in an acidic solution?

when salts have a strong acid and/or weak base

What is Kw in relation to Ka and Kb

Kw=KaKb

What happens when a salt is derived from both a weak acid and base? How is acidity determined?

both the cation and anion hydrolyze, aciditiy is determined by whether Ka or Kb is larger

lower temperature on pH and Kw (explain in chatalier’s principle)

pH rises above 7 but is still neutral, Kw lowers because heat, a reactant, is reduced, causing a shift to reactants

higher temperature on pH and Kw (explain in chatalier’s principle)

pH lowers below 7 but is still neutral, Kw raises because heat, a reactant, is increased, causing a shift to products

What is the order of Ka when polyprotic acids are ionized? What is the exception?

Ka1>Ka2>Ka3, second ionization doesn’t affect pH too much except sulfuric acid

when two strong acids are combined, what happens?

the stronger acts as an acid while the weaker acts as a base

how does the common ion affect equilibrium?

since there are more ions in products, it will shift to reactants, preventing further ionization

look at the following reaction. describe what happens with CH3COOH + CH3COONa?

there will be more ions in products than H+ protons, thus shifting equilibrium to the left, and decreasing Ka

what is the henderson-hasselbalch equation?

pH=pKa+log(conj base/acid)

buffer solutions

resist change in pH up to a point

imagine a buffer of HA and A-. describe what happens if a strong acid is added

the proton of the strong acid will combine with A-, the weak base, and results in more HA than A-

imagine a buffer of HA and A-. describe what happens if a strong base is added

the proton from HA will be taken by the stong base, resultins in more A- than HA

what is and isn’t a simple buffer solution generally made of?

a weak acid/base with its conjugate base/acid , no strong acids/bases

how to calcualte pH of buffers?

pH = pKa+log(initial conjugate base conc/initial acid conc)