CHEM 1152 – Quiz #9 – Spring 2002 – Dr. Thrush
Name: ________________________________________________________
April 5, 2002
INSTRUCTIONS: Clearly print your name on the top line. Point values are given for each problem. For all
multiple choice questions, please circle the correct answer. Show all work – partial credit will be given.
Be sure to give all numerical answers in the proper number of significant figures and the correct
units.
Potentially Useful Information:
x=
-b ± √ b2 – 4ac
Kw = 1.0 x 10-14
2a
pH = pKa + log [base]
[acid]
1. (4 points) Which species listed below is present in the greatest concentration in a 0.1 M solution of
CH3COONa?
A.
B.
C.
D.
E.
CH3COONa
CH3COONa+
CH3COOH
OH-
2. (7 points) Calculate the pH of a buffer solution, which contains 0.50 M benzoic acid (C6H5COOH) and
0.15 M sodium benzoate (C6H5COONa). Given Ka = 6.5 x 10-5.
pH = _____________
Will this buffer solution have more capacity for neutralizing added acid or added base? Why?
3. (5 points) Methyl red is a common acid-base indicator. It has a Ka = 6.3 x 10-6. Its undissociated form
is red and its anionic form is yellow. What color would a methyl red solution have at pH = 7.8? Why?
4. (6 points) The solubility of lead iodide is 0.064 g / 100 ml at 20°C. What is the solubility product for
PbI2? Atomic Weight of Pb = 207.2 amu and Atomic Weight of I = 126.9 amu.
5. (8 points) Write the net reactions that occur in a CO32- / HCO3- buffer solution when:
(a) a strong acid is added
(b) a strong base is added
CHEM 1152 – Quiz #9 – Spring 2002 – Dr. Thrush
Name: ________________________________________________________
April 5, 2002
INSTRUCTIONS: Clearly print your name on the top line. Point values are given for each problem. For all
multiple choice questions, please circle the correct answer. Show all work – partial credit will be given.
Be sure to give all numerical answers in the proper number of significant figures and the correct
units.
Potentially Useful Information:
x=
-b ± √ b2 – 4ac
Kw = 1.0 x 10-14
2a
pH = pKa + log [base]
[acid]
1. (5 points) Methyl red is a common acid-base indicator. It has a Ka = 6.3 x 10-6. Its undissociated form
is red and its anionic form is yellow. What color would a methyl red solution have at pH = 7.8? Why?
2. (8 points) Write the net reactions that occur in a CO32- / HCO3- buffer solution when:
(a) a strong acid is added
(b) a strong base is added
3. (4 points) Which species listed below is present in the greatest concentration in a 0.1 M solution of
CH3COONa?
A.
B.
C.
D.
E.
CH3COOH
CH3COOOHNa+
CH3COONa
4. (7 points) Calculate the pH of a buffer solution, which contains 0.15 M benzoic acid (C6H5COOH) and
0.50 M sodium benzoate (C6H5COONa). Given Ka = 6.5 x 10-5.
pH = _____________
Will this buffer solution have more capacity for neutralizing added acid or added base? Why?
5. (6 points) The solubility of lead iodide is 0.064 g / 100 ml at 20°C. What is the solubility product for
PbI2? Atomic Weight of Pb = 207.2 amu and Atomic Weight of I = 126.9 amu.