Acids/Bases
What is the Bronsted-Lowry definition of an acid?
a compound that donates a proton
The concentration of hydroxide ions, [OH-], of window cleaner is 0.0020 mol/L at 250C. What is the concentration of hydronium ions, [H3O+], in the sample? Is the window cleaner acidic, basic, or neutral?
[H3O+] = 5.0x10-12 mol/L
[OH-]>[H3O+]; solution is basic
Calculate the Kb value for the conjugate base of hydrosulfuric acid (Ka = 8.9x10-8).
Kb = 1.1x10-7
Buffered solutions contain a mixture of...
A weak acid and its conjugate base OR
a weak base and its conjugate acid
Write the equilibrium reaction and the equilibrium expression for the dissolving of silver carbonate.
Ag2CO3(s) <--> 2Ag+ + CO3+2
Ksp = [Ag+]2[CO3+2]
What is the conjugate acid of this reaction:
HCl + NH3 <--> NH4+ + Cl-
NH4+
If a solution has a hydronium concentration of 3.2x10-4 mol/L, what is the pH of the solution?
pH = 3.49
Calculate the Ka value for the conjugate acid of dimethylamine (Kb = 5.4x10-4).
Ka = 1.9x10-11
resists change in pH
Determine the concentrations of calcium ions and carbonate ions at equilibruim, if Ksp for calcium carbonate is 3.36x10-9.
[Ca+2] = [CO3-2] = 5.80x10-5 mol/L
Complete this reaction and identify the acid and conjugate base:
HF + H2O <-->
HF + H2O <--> H3O+ + F-
acid = HF
conjugate base = F-
A solution was prepared with [H3O+] of 0.50 mol/L. What is the pH, pOH, and [OH-] of the solution?
pH = 0.30
pOH = 13.70
[OH-] = 2.0x10-14 mol/L
Write the Ka expression for sulfuric acid.
Ka = [HSO4-][H+]/[H2SO4]
Suggest a salt that could be combined with acetic acid, CH3COOH(aq) to form a buffer.
Answers may vary
(ie. sodium acetate)
The Ksp for barium fluoride, BaF2, is 1.7x10-6. What is its molar solubility? How soluble is barium fluoride?
7.5x10-3 mol/L
solubility is low
The greater the number of oxygen atoms, the stronger the acid
Determine the pH of 0.12 mol/L of NaOH solution at 250C.
pH = 13.08
(pOH = 0.92)
Write the Kb expression for ammonia (NH3).
Kb =[NH4+][OH-] /[NH3]
Write the hydrolysis reaction equation for each ion and determine whether the ion forms an acidic or basic solution?
1) CO32-
2) NH4+
1) CO32- (aq) + H2O(l) ↔ H2CO3(aq) + OH-(aq) = basic
2) NH4+(aq) + H2O(l) ↔ NH3(aq) + H3O+(aq) = acidic
If exactly 200mL of 0.0040 mol/L barium chloride solution, BaCl2(aq), is mixed with exactly 600 mL of 0.0080 mol/L potassium sulfate solution, K2SO4(aq), the particles dissociate, and the only possible precipitate that can form is BaSO4(s) (Ksp = 1.08x10-10). Will a precipitate form?
Qsp = 6.0x10-6
Qsp > Ksp
A precipitate forms
When given the salt of an acid/base reaction, how do you determine if the solution of the salt will be acidic, basic, or neutral?
SA + WB = acidic
SA + SB = neutral
WA + SB = basic
WA + WB = determine Ka and Kb
Using your knowledge of strong/weak acids and bases, predict if the solution for the following salts are acidic, basic, or neutral:
1) LiBr
2) CaS
3) NH4I
1) neutral
2) basic
3) acidic
A 0.10 mol/L solution of propanoic acid, C2H5COOH(aq), is prepared. The pH of the solution is 2.96. Determine the Ka.
Ka = 1.2x10-5
The Ka for four acids are: H2SO3 1.4x10-2, H2S 8.9x10-8, HF 6.3x10-4, C6H8O6 9.1x10-5.
The pH's of 0.75 mol/L of each solution of these acids were measured. List the acids in order from the highest pH to the lowest pH.
H2S
C6H8O6
HF
H2SO3
To determine the Ksp for silver nitrate, a piece of zinc is placed into 1.0L of saturated solution of silver nitrate at room temperature. After a day, there is 0.35g less of the zinc piece than when the experiment first began. What is the Ksp for silver nitrate at room temperature?
moles of the Zn reacted = 5.35x10-3 mol
Balanced equation = Zn(s) + 2AgNO3(aq) --> 2Ag(s) + Zn(NO3)2(aq)
Original concentration of the silver ions = 2(5.35x10-3) = 1.07x10-2
Ksp = 1.14x10-4