Page 194 - Modern Analytical Chemistry

1400-CH06 9/9/99 7:41 AM Page 177

Chapter 6 Equilibrium Chemistry 177

3. Calculate the potential for the following redox reaction when Calculate the solubility of CaF 2 in a solution buffered to a pH
2+
2+
3+
the [Fe ] = 0.050 M, [Fe ] = 0.030 M, [Sn ] = 0.015 M and of 7.00. Use a ladder diagram to help simplify the calculations.
4+
[Sn ] = 0.020 M How would your approach to this problem change if the pH
is buffered to 2.00? What is the solubility of CaF 2 at this pH?
3+
2+
2+
4+
2Fe (aq)+Sn (aq) t Sn (aq) + 2Fe (aq)
11. Calculate the solubility of Mg(OH) 2 in a solution buffered to
4. Balance the following redox reactions, and calculate the a pH of 7.00. How does this compare with its solubility in
standard-state potential and the equilibrium constant for unbuffered water?
+
each. Assume that the [H 3 O ] is 1 M for acidic solutions, and
–
that the [OH ] is 1 M for basic solutions. 12. Calculate the solubility of Ag 3 PO 4 in a solution buffered to a
–
2+
a. MnO 4 (aq)+H 2 SO 3 (aq) t Mn (aq)+ pH of 9.00.
2–
SO 4 (aq) (acidic solution) 13. Determine the equilibrium composition of saturated solution
–
–
b. IO 3 (aq)+I (aq) t I 2 (s) (acidic solution) of AgCl. Assume that the solubility of AgCl is influenced by
–
–
–
–
c. ClO (aq)+I t IO 3 (aq)+Cl (aq) (basic solution) the following reactions.
5. Sulfur can be determined quantitatively by oxidizing to AgCl(s) t Ag (aq)+Cl (aq)
–
+
2–
SO 4 and precipitating as BaSO 4 . The solubility reaction
+
–
for BaSO 4 is Ag (aq)+Cl (aq) t AgCl(aq)
2–
2+
–
–
BaSO 4(s) t Ba (aq)+SO 4 (aq) AgCl(aq)+Cl (aq) t AgCl 2 (aq)
How will the solubility of BaSO 4 be affected by (a) decreasing 14. Calculate the ionic strength of the following solutions
the pH of the solution; (b) adding BaCl 2 ; (c) decreasing the a. 0.050 M NaCl
volume of the solution? b. 0.025 M CuCl 2
c. 0.10 M Na 2 SO 4
6. Write charge balance and mass balance equations for the
following solutions 15. Repeat the calculations in problem 9, this time correcting for
a. 0.1 M NaCl activity effects.
b. 0.1 M HCl 16. With the permission of your instructor, carry out the
c. 0.1 M HF following experiment. In a beaker, mix equal volumes of
d. 0.1 M NaH 2PO 4 0.001 M NH 4 SCN and 0.001 M FeCl 3 (the latter solution
e. MgCO 3 (saturated solution) must be acidified with concentrated HNO 3 at a ratio of 4
–
f. 0.1 M Ag(CN) 2 (from AgNO 3 and KCN) drops/L to prevent the precipitation of Fe(OH) 3 ). Divide
g. 0.1 M HCl and 0.050 M NaNO 2 solution in half, and add solid KNO 3 to one portion at a
7. Using the systematic approach, calculate the pH of the ratio of 4 g per 100 mL. Compare the colors of the two
following solutions solutions (see Color Plate 3), and explain why they are
different. The relevant reaction is
a. 0.050 M HClO 4
–7
b. 1.00 ´10 M HCl Fe (aq) + SCN (aq) t Fe(SCN) (aq)
–
2+
3+
c. 0.025 M HClO
d. 0.010 M HCOOH 17. Over what pH range do you expect Ca 3 (PO 4 ) 2 to have its
minimum solubility?
e. 0.050 M Ba(OH) 2
f. 0.010 M C 5 H 5N 18. Construct ladder diagrams for the following systems, and
8. Construct ladder diagrams for the following diprotic weak describe the information that can be obtained from each
acids (H 2L), and estimate the pH of 0.10 M solutions of H 2L, a. HF and H 3 PO 4
– 2– 4–
2–
–
HL , and L . Using the systematic approach, calculate the pH b. Ag(CN) 2 , Ni(CN) 4 and Fe(CN) 6
3+
2–
3+
of each of these solutions. c. Cr 2 O 7 /Cr and Fe /Fe 2+
a. maleic acid 19. Calculate the pH of the following acid–base buffers
b. malonic acid a. 100 mL of 0.025 M formic acid and 0.015 M sodium
c. succinic acid formate
9. Ignoring activity effects, calculate the solubility of Hg 2 Cl 2 in b. 50.00 mL of 0.12 M NH 3 and 3.50 mL of 1.0 M HCl
the following c. 5.00 g of Na 2 CO 3 and 5.00 g of NaHCO 3 in 0.100 L
a. A saturated solution of Hg 2Cl 2 20. Calculate the pH of the buffers in problem 19 after adding
–4
b. 0.025 M Hg 2(NO 3) 2 saturated with Hg 2Cl 2 5.0 ´10 mol of HCl.
c. 0.050 M NaCl saturated with Hg 2Cl 2 21. Calculate the pH of the buffers in problem 19 after adding
–4
10. The solubility of CaF 2 is controlled by the following two 5.0 ´10 mol of NaOH.
reactions 22. Consider the following hypothetical complexation reaction
2+
–
CaF 2 (s) t Ca (aq)+F (aq) between a metal, M, and a ligand, L
+
–
HF(aq)+H 2 O(l) t H 3 O (aq) +F (aq) M(aq)+L(aq) t ML(aq)