"Solubility and Complex Equilibria Worksheet With Answer Key - Chemistry 1b, Siraj Omar, Berkeley City College"

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Chem 1B
Name:_______________________
Chapter 16 Exercises
Solubility and Complex Equilibria
1.
Determine the solubility in (i) in mol/L, and (ii) in gram/L of each of the following salts:
10
(a) AgCl, K
= 1.6 x 10
sp
13
(b) AgBr, K
= 5.0 x 10
sp
12
(c) Ag
CrO
, K
= 9.0 x 10
2
4
sp
o
2.
The solubility of calcium hydroxide, Ca(OH)
, in water at 25
C is 0.51 g/L. Determine the solubility
2
product constant (K
) for calcium hydroxide.
sp
3.
A saturated solution of magnesium hydroxide, Mg(OH)
, has a pH = 10.42. What is the solubility of
2
Mg(OH)
in mol/L? Determine the K
of magnesium hydroxide.
2
sp
32
4.
Calcium phosphate, Ca
(PO
)
, has solubility product, K
= 1.3 x 10
. (a) What are the concentrations
3
4
2
sp
2+
3
of Ca
and PO
, respectively, in a saturated solution of Ca
(PO
)
. (b) If a hard water contains 75 ppm
4
3
4
2
2+
3
(75 mg/L) of Ca
, at what concentration of PO
would a precipitate of Ca
(PO
)
begin to appear?
4
3
4
2
5.
A solution containing 0.010 M AgNO
and 0.050 M Pb(NO
)
is titrated with 0.050 M NaCl solution.
3
3
2
(a) At what concentration of Cl
(i) AgCl begins to precipitate; (ii) PbCl
begins to precipitate?
2
+
(b) Determine the concentration Ag
in solution when the precipitation of PbCl
begins.
2
10
6.
Determine the solubility of AgCl (K
= 1.6 x 10
) in 0.010 M NaCl solution.
sp
7.
(a) Will precipitate of PbCl
form when a 30.0-mL solution of 0.20 M NaCl is added 20.0 mL of 0.20 M
2
2+
Pb(NO
)
solution? (b) If precipitate is formed, what are the concentrations of Pb
and Cl
,
3
2
respectively, in the saturated solution of PbCl
? (c) Determine if a precipitate will form if the initial
2
5
concentrations of Pb(NO
)
and NaCl were each 0.020 M? (K
= 1.6 x 10
).
3
2
sp
1
Chem 1B
Name:_______________________
Chapter 16 Exercises
Solubility and Complex Equilibria
1.
Determine the solubility in (i) in mol/L, and (ii) in gram/L of each of the following salts:
10
(a) AgCl, K
= 1.6 x 10
sp
13
(b) AgBr, K
= 5.0 x 10
sp
12
(c) Ag
CrO
, K
= 9.0 x 10
2
4
sp
o
2.
The solubility of calcium hydroxide, Ca(OH)
, in water at 25
C is 0.51 g/L. Determine the solubility
2
product constant (K
) for calcium hydroxide.
sp
3.
A saturated solution of magnesium hydroxide, Mg(OH)
, has a pH = 10.42. What is the solubility of
2
Mg(OH)
in mol/L? Determine the K
of magnesium hydroxide.
2
sp
32
4.
Calcium phosphate, Ca
(PO
)
, has solubility product, K
= 1.3 x 10
. (a) What are the concentrations
3
4
2
sp
2+
3
of Ca
and PO
, respectively, in a saturated solution of Ca
(PO
)
. (b) If a hard water contains 75 ppm
4
3
4
2
2+
3
(75 mg/L) of Ca
, at what concentration of PO
would a precipitate of Ca
(PO
)
begin to appear?
4
3
4
2
5.
A solution containing 0.010 M AgNO
and 0.050 M Pb(NO
)
is titrated with 0.050 M NaCl solution.
3
3
2
(a) At what concentration of Cl
(i) AgCl begins to precipitate; (ii) PbCl
begins to precipitate?
2
+
(b) Determine the concentration Ag
in solution when the precipitation of PbCl
begins.
2
10
6.
Determine the solubility of AgCl (K
= 1.6 x 10
) in 0.010 M NaCl solution.
sp
7.
(a) Will precipitate of PbCl
form when a 30.0-mL solution of 0.20 M NaCl is added 20.0 mL of 0.20 M
2
2+
Pb(NO
)
solution? (b) If precipitate is formed, what are the concentrations of Pb
and Cl
,
3
2
respectively, in the saturated solution of PbCl
? (c) Determine if a precipitate will form if the initial
2
5
concentrations of Pb(NO
)
and NaCl were each 0.020 M? (K
= 1.6 x 10
).
3
2
sp
1
Chem 1B
Name:_______________________
Chapter 16 Exercises
8.
Which of the following compounds the solubility is influenced by the pH of the solution?
Write chemical equations that show how pH will increase (or decrease) their solubility.
(a) PbCl
2
(b) PbCO
3
(c) CaF
2
(d) Ag
PO
3
4
(e) AgBr
–12
9.
Calculate the solubility (in mol/L) of magnesium hydroxide (Mg(OH)
; K
= 8.9 x 10
) in a solution
2
sp
buffered at pH 10.00?
–10
10.
What is the solubility of silver chloride (K
= 1.6 x 10
) in water and in 3.0 M NH
solution,
sp
3
+
+
7
respectively? [Ag
+ 2NH
Ag(NH
)
, K
= 1.7 x 10
]
(aq)
(aq)
(aq)
3
3
2
f
11.
Certain transition metal cations have the ability to form complex ions with ammonia (NH
) and
3
-
hydroxide ion (OH
). The formation of complex ions significantly increases the solubility of slightly
soluble compounds containing these cations. Identify compounds from the following list which
solubility will significantly increase: (i) in excess NH
, and (ii) in excess NaOH solution.
3
(a) Cr(OH)
3
(b) Fe(OH)
3
(c) Cu(OH)
2
(d) Zn(OH)
2
(e) AgOH
(f) Pb(OH)
2
+
2+
12.
A solution contains Ag
and Ba
ions. What reagents would you use to separate and extract the two
cations from the mixture? Explain your choice of the reagents and the process involved.
2
Chem 1B
Name:_______________________
Chapter 16 Exercises
13.
In a qualitative experiment, you are given a solution that contains a mixture of the following cations:
+
2+
3+
3+
2+
Ag
, Ba
, Cr
, Fe
, and Cu
. Create a flow chart to show how these cations are separated. Indicate
specific reagents used in each separation step.
(Available reagents are 0.1 M NaCl, 0.1 M Na
SO
, 6 M HNO
, 6 M NaOH, and 6 M NH
)
2
4
3
3
14.
Given the following equilibria:
–13
+
AgBr
Ag
+ Br
;
K
= 5.0 x 10
(s)
(aq)
(aq)
sp
+
2–
8
Ag
+ S
O
Ag(S
O
)
;
K
= 7.4 x 10
(aq)
(aq)
(aq)
2
3
2
3
f1
2–
3–
4
Ag(S
O
)
+ S
O
Ag(S
O
)
;
K
= 3.9 x 10
(aq)
(aq)
(aq)
2
3
2
3
2
3
2
f2
(a) What is the equilibrium constant (K
) for the following equilibrium?
c
2–
3–
AgBr(s) + 2S
O
Ag(S
O
)
+ Br
(aq)
(aq)
(aq)
2
3
2
3
2
(b) Calculate the solubility of AgBr (in mol/L) in 0.50 M Na
S
O
solution.
2
2
3
(c) How many grams of AgBr will dissolve in 100. mL of 0.50 M Na
S
O
?
2
2
3
15.
Given the following equilibria:
–10
+
AgCl
Ag
+ Cl
;
K
= 1.6 x 10
(s)
(aq)
(aq)
sp
+
+
7
Ag
+ 2NH
Ag(NH
)
;
K
= 1.7 x 10
(aq)
(aq)
(aq)
3
3
2
f
(a) Calculate the equilibrium constant, K
, for the following eqiolibrium:
c
+
AgCl
+ 2NH
Ag(NH
)
+ Cl
(s)
(aq)
(aq)
(aq)
3
3
2
(b) Predict whether precipitates of AgCl will form when each of the following solutions are mixed.
(i) 5.0 mL of 0.10 M AgNO
+ 5.0 mL of 0.20 M NaCl
+ 10.0 mL of 1.0 M NH
;
(aq)
(aq)
(aq)
3
3
(ii) 5.0 mL of 0.10 M AgNO
+ 5.0 mL of 0.20 M NaCl
+ 10.0 mL of 2.0 M NH
;
(aq)
(aq)
(aq)
3
3
+
2+
16.
What are the equilibrium concentrations of Na
, NO
, Pb
, and Br
, respectively, in an equilibrium
3
obtained by mixing equal volumes of 0.10 M Pb(NO
)
and 0.20 M NaBr?
3
2
–6
(PbBr
has K
= 4.6 x 10
)
2
sp
17.
Explain how you would separate the cations in each of the following mixtures using only one reagent.
(For each mixture, find specific reagents that would cause the precipitation of one of the cations, but not
the other. (Hint: use solubility rules and K
values.)
sp
3+
2+
3+
2+
+
2+
2+
2+
(a) Al
from Mg
;
(b) Fe
from Cu
;
(c) Ag
from Pb
;
(d) Cu
from Zn
;
3
Chem 1B
Name:_______________________
Chapter 16 Exercises
Answers:
5
3
7
5
1.
(a) (i) 1.3 x 10
mol/L; (ii) 1.8 x 10
g/L;
(b) (i) 7.1 x 10
mol/L; (ii) 8.2 x 10
g/L;
4
2
(c) (i) 1.3 x 10
mol/L; (ii) 4.3 x 10
g/L
3
6
2.
Solubility = 6.9 x 10
mol/L;
K
= 1.3 x 10
sp
4
12
3.
Solubility = 1.3 x 10
mol/L;
K
= 9.1 x 10
sp
2+
7
3
7
3
12
4.
(a) [Ca
] = 4.9 x 10
M; [PO
] = 3.2 x 10
M;
(b) [PO
] = 2.6 x 10
M
4
4
8
2
5.
(a) (i) [Cl
] = 1.6 x 10
M AgCl begins to ppt; (ii) [Cl
] = 1.8 x 10
M, PbCl
begins to ppt;
2
2
+
9
(b) If [Cl
] = 1.8 x 10
M, [Ag
] = 8.9 x 10
M
8
6.
Solubility = 1.6 x 10
mol/L
3
,  precipitate will form;
7.
(a) Q
= 1.2 x 10
> K
sp
sp
2+
(b) [Pb
] = 0.031 M; [Cl
] = 0.023 M;
(solved using iteration method)
6
 precipitate will NOT form.
(c) Q
= 1.2 x 10
< K
sp
sp
2+
2
2
+
8.
(b) PbCO
Pb
+ CO
;
CO
+ 2H
H
O + CO
(s)
(aq)
(aq)
(aq)
(aq)
(g)
3
3
3
2
2
2
Acid reacts with CO
, HCO
or H
O and CO
; more solids dissolve to maintain equilibrium;
3
3
2
2
2+
+
(c) CaF
Ca
+ F
;
F
+ H
HF
(s)
(aq)
(aq)
(aq)
(aq)
(aq)
2
2
-
Acid reacts with F
; more solid CaF
dissolves to compensate loss of F
and maintain equilibrium;
2
+
3
3
+
2
(d) Ag
PO
3Ag
+ PO
;
PO
+ H
HPO
;
(s)
(aq)
(aq)
(aq)
(aq)
(aq)
3
4
4
4
4
3
2
3
Acid converts PO
HPO
PO
decreases; more solid to dissolve to maintain equilibrium.
to
; [
]
4
4
4
eq
–4
9.
Solubility = 8.9 x 10
mol/L
5
10.
Solubility of AgCl = 1.3 x 10
mol/L in water; and 0.14 mol/L in 3.0 M NH
;
3
2+
11.
Compounds soluble in NH
: (c) Cu(OH)
(s) + 4NH
(aq)
Cu(NH
)
(aq) + 2 OH
(aq);
3
2
3
3
4
+
(e) AgOH(s) + 2NH
(aq)
Ag(NH
)
(aq) + OH
(aq);
3
3
2
Compounds soluble in excess NaOH: (a) Cr(OH)
(s) + OH
(aq)
Cr(OH)
(aq);
3
4
2
2
.
(d) Zn(OH)
+ 2OH
(aq)
Zn(OH)
(aq)
;
(f) Pb(OH)
(s) + 2OH
(aq)
Pb(OH)
(aq)
2
4
2
4
2+
remains in solution – BaCl
2+
12.
Add HCl or NaCl; AgCl will form ppt and Ba
m is soluble; Ba
can be
2
extracted using Na
SO
to form BaSO
ppt.
2
4
4
+
2+
3+
3+
2+
13.
Mixture-#1: ( Ag
+ Ba
+ Cr
+ Fe
+ Cu
) + NaCl(aq)
precipitate AgCl(s); Centrifuge;
2+
3+
3+
2+
Mixture-#2: (Ba
+ Cr
+ Fe
+ Cu
) + Na
SO
(aq)
precipitate BaSO
(s); Centrifuge;
2
4
4
3+
3+
2+
2+
Mixture-#3: (Cr
+ Fe
+ Cu
) + exs NH
Cr(OH)
+ Fe(OH)
+ Cu(NH
)
; Centrifuge;
(s)
(s)
(aq)
3
3
3
3
4
Mixture-#4: (Cr(OH)
+ Fe(OH)
) + exs NaOH
Cr(OH)
+ Fe(OH)
; Centriguge
(s)
(s)
(aq)
(aq)
(s)
3
3
4
3
14.
(a) K
= 14; (b) solubility = 0.22 mol/L; (c) 4.1 g
c
3
3
 ppt forms; (b) Q
3
 no ppt;
15.
K
= 2.7 x 10
; (a) Q
= 5.0 x 10
> K
= 1.3 x 10
< K
c
c
c
c
c
2+
+
16.
[Pb
] = 0.010 M; [Br
] = 0.021 M; [Na
] = 0.10 M; [NO
] = 0.10 M;
3
2+
17.
(a) Add buffered NH
-NH
Cl; pH~9.5; precipitate of Al(OH)
(s) is formed; Mg
remains in solution;
3
4
3
2+
(b) Add excess NH
; Fe(OH)
(s) is formed, Cu(NH
)
remains in solution;
3
3
3
4
(c) Add NaCl and heat mixture; PbCl
(s) dissolves when heated, AgCl(s) remains as precipitate;
2
(d) Add excess NaOH(aq); Cu(OH)
(s) is formed; Zn(OH)
is soluble in excess OH
(aq)
2
2
4