Acids, Bases, and Salts
Equilibria
Buffers
Titrations
100
How can you relate Ka and Kb?
Ka*Kb = Kw = E-14
100
What is the pH of a 0.534 M solution of formic acid? (HCO2H Ka = 1.8E-4)
pH = 2.01
100
What happens to the pH of an acidic buffer solution when we add a small amount of a strong base?
It doesn't change much.
100
What is a titration curve?
A titration curve is a plot of some solution property versus the amount of added titrant.
200
Determine which species are acting as a Lewis acid and Lewis base for the following reaction:
ZnCO3(s) + 4NH3(aq) --> Zn(NH3)42+(aq) + CO32-(aq)
Lewis acid: Zn2+
Lewis base: NH3
200
Find the pOH of a 0.25 M solution of (CH3)3N. (Kb = 6.3E-5)
pOH = 2.40
200
What is a buffer capacity?
The amount of acid or base that can be added to a buffer before the pH changes significantly.
200
What is the equivalence point?
It's the point during titration when the moles of the acid are equal to the moles of the base.
300
Which of the following acids has the strongest conjugate base?
a) H2Se
b) H2S
c) H2Te
d) H2O
d) H2O
300
What is the pH of a 0.50 M solution of NaHSO4, a weak base? (Ka = 1.2E-2)
pH = 1.14
300
Select an approximate weak base to make a buffer with a pH of 8.49. How many moles of the salt will you need to add if you have 1.0 L of a 0.175 M basic solution? (NH3 Kb = 1.8E-5, C5H5N Kb = 1.7E-9, (C2H5)3N Kb = 5.6 E-4)
a) NH3, 1.030 mol salt
b) (C2H5)3N, 0.551 mol salt
c) C5H5N, 0.73 mol salt
d) (C2H5)3N, 0.057 mol salt
e) NH3, 0.030 mol salt
a) NH3, 1.030 mol salt
300
Which titration curve would describe mixing 22 mL of 0.245 M sertraline (C17H17Cl2N, Ka = 3.2E-4) with 0.125 M HClO4? Is pH at the equivalence point greater than, less, or equal to 7?
Second graph, pH < 7.
400
How many acidic hydrogens are there in malonic acid, HOOCCH2COOH?
2
400
What is the %ion of a solution of 0.716 M lactic acid (HC3H5O3, pKa = 3.85)?
1.40%
400
You have a beaker with 5.0 mL of 0.1 M CH3CH2COONa. You add 5.0 mL of 0.1 M HClO4. What is the type of the solution before and after the addition of HClO4?
Before: basic salt
After: weak acid
400
Calculate the pH of 22 mL of 0.245 M sertraline (C17H17Cl2N, Kb = 3.2E-4) titrated with 17.5 mL of 0.125 M HClO4.
pH = 10.67
500
Identify the molecules as acidic, basic, or amphoteric. List their conjugate acid, or base (or both).
C6H5NH2, CH2ClCOOLi, (CH3)3NHNO3, H2O, HOOCCH2COO-, CH3CH2COOH
C6H5NH2 - basic, CA: C6H5NH3+
CH2ClCOO-|Li+ - basic, CA: CH2ClCOOH
(CH3)3NH+|NO3- - acidic, CB: (CH3)3N
H2O - amphoteric, CA: H3O+,CB: OH-
HOOCCH2COO- - amphoteric, CA: HOOCCH2COOH, CB: -OOCCH2COO-
CH3CH2COOH - acidic, CB: CH3CH2COO-
500
Calculate the pH of a 0.10 M Al(H2O)63+. (Ka = 1.4E-5)
pH = 2.92
500
Calculate the pH of a solution that contains 50 mL of 0.095 M (CH3CH2)2 and 20 mL of 0.17 M HNO3. (Kb = 5.9E-4)
pH = 10.37
500
What is the pH at the equivalence point of the titration of 22 mL of 0.245 M sertraline (C17H17Cl2N, Ka = 3.2E-4) with 0.125 M HClO4.
pH = 5.79