Gen. Chem. Exam 3 Prep

Acidic, Basic, or Neutral Salts

100

What makes anions acidic?

being a conjugate base of a weak acid

200

What is used to determine the pH of salts if one is acidic and the other is basic?

K_a and K_b

300

Is this salt acidic, basic, or neutral:

NaI

neutral

400

Is the salt acidic, neutral, or basic:

NH₄NO₃

Acidic

500

Is the salt acidic, basic, or neutral

Pb(CN)₄

K_a=10^-6

K_b=2.5*10^-5

Basic

Weak Acids

100

What is the general equation of ionization Weak Acids

Ha + H2O ↔ A^- + H3O⁺

200

What is the equilibrium constant expression for weak acids

K_a = [H₃O⁺][A^-]/[HA]

300

Benzoic acid, HC₇H₅O₂, is a weak monoprotic acid. What is the K_a if we have .0500 M with a pH of 2.876?

3.63*10^-5

400

Acetic acid, HC₂H₃O₂, is a weak monoprotic acid. What is the pH if the Ka=1.75*10^-5 and we have .645M?

2.47

500

What is the % ionization of the last problem? 

Acetic acid, HC₂H₃O₂, is a weak monoprotic acid. What is the pH if the Ka=1.75*10^-5 and we have .645M?

.34%

Weak Bases

100

What is the general equation of ionization for Weak Bases

B + H2O ↔ HB⁺ + OH^-

200

What is the equilibrium constant expression for weakbases

K_b=[OH^-][HB⁺]/[B]

300

Quinine is a weak base. what is the K_b if we have .00962 M with a pH of 11.96?

.166 M

400

Methylamine, CH₃NH₂, is a weak base. what is the pH if the K_b=4.4*10^-4 and we have .348 M?

12.08

500

What is the % ionization of the last problem?

Methylamine, CH₃NH₂, is a weak base. what is the pH if the K_b=4.4*10^-4 and we have .348 M?

1.2%

Buffers/Titrations

100

Are buffers completely resistant to pH changes or are they just resistant to pH changes? How?

just resistant

conj. base can react with a H⁺ donor added to the system, conj. acid reacts with a H⁺ acceptor to the system and can self balance

200

What is the Henderson-Hasselbach equation? Where can it be used?

pH=-log(Ka)+log([A^-]/[HA])

300

If we are doing a titration of a weak base with a strong acid, where would we think the end point would lie?

below 7

400

When doing a titration with a weak polyprotic acid, are there multiple equivalence points? If so why?

yes there is, due to the H being reacted with. the first H is reacted, first equivalence point, then another is reacted with, a second equivalence point, and so on.

500

What is the pH of a buffer that contains a mixture of .265 M of HNO₂ and .197 M of NO₂^-? K_a=7.1*10^-5

4.022

Common Ion Effect and Weakly Soluble Salts

100

What is the chemical equations and K_sp equation for Ca(OH)₂?

Ca(OH)_2(s) ↔ Ca²⁺_(aq)+2OH^-_(aq)

K_sp=[Ca²⁺][OH^-]²

200

If I add CaCO₃ to Ca(OH)₂, will the solubility not change or decrease?

decrease

300

If I add NaOH to CaCO₃, will the solubility not change or decrease

no

400

What is the K_sp of Mercury (II) Bromide if HgBr₂=4.9*10^-3?

4.71*10^-7

500

What is the concentration of Iron (III) Hydroxide if the K_sp=2*10^-39 and what is the solubility of Fe(OH)₃ in g/200 mL

MM=106.867

9.28*10^-11 M

1.98*10^-9 g/200mL