CHM 2046
Exam 2
March 9, 2006
Bubble in A, B or C as the test form code at the top right of your answer sheet.
VERSION 0
For this version the correct answer to each question is a.
Predict the sign of ΔSºrxn for the following reaction: 2 C (s) + O2 (g) → 2 CO (g)
a.
positive
b.
depends on ΔSuniv
c.
negative
d.
cannot be predicted
e.
zero
1.
2.
What is the solubility of the salt M2X3 (containing M3+ and X2- ions) if its Ksp = 2.6 x 10-4?
a.
b.
c.
d.
e.
3.
7.5 x 10-2 M
1.3 x 10-1 M
1.9 x 10-1 M
2.6 x 10-4 M
none of these
Addition of which of the following very soluble salts is most likely to increase the
solubility of MgCO3 in water?
a.
b.
c.
d.
e.
NH4Cl
KCl
Na2CO3
MgI2
NaNO3
4.
Which of the following substances will have the greatest molar entropy?
a.
C3H8 (g)
b.
CH4 (g)
c.
C6H6 (l)
d.
C2H6 (g)
e.
C4H10 (l)
5.
Which of the following is always true for a spontaneous reaction?
a.
b.
c.
d.
e.
6.
A solution is prepared that contains [Pb2+ (aq)] = 1.4 x 10-2 M, and [I- (aq)] = 2.0 x 10-4 M.
Will a precipitate of PbI2 (s) form? (Ksp for PbI2 is 7.9 x 10-9).
a.
b.
c.
d.
e.
7.
none of these
ΔSsurr > 0
ΔSrxn > 0
ΔSrxn < 0
ΔSuniv > ΔSrxn + ΔSsurr
no
none of the other answers
only if Na+ (aq) ions are also added
yes
cannot be determined
The solubility product expression (Ksp) for BaF2 (s) in water is:
a.
b.
c.
d.
e.
Ksp = [Ba2+ (aq)][F- (aq)]2
none of these
Ksp = [Ba2+ (aq)][F- (aq)]
Ksp = [Ba2+ (aq)][F- (aq)]2/[BaF2 (s)]
Ksp = [Ba2+ (aq)][F- (aq)]/[BaF2 (s)]
8.
Calculate the pH when 100 mL of 0.100 M Ca(OH)2 solution is added to 200 mL of 0.200
M HCl solution.
a.
b.
c.
d.
e.
9.
The following reaction has ΔSºrxn = 197.9 J/K and ΔHºrxn = 49.7 kJ. Is the reaction
spontaneous as written?
A (g) + B (g) → products
a.
b.
c.
d.
e.
10.
AlCl3 (s) dissolving in water
a solid warming from 10 ºC to 20 ºC
a tennis ball falling
ice at 0 ºC melting to water at 0 ºC
none of these
Calculate ΔSº for the reaction: H2 (g) + Cl2 (g) → 2 HCl (g)
Sº values (J/mol.K): H2 (g) = 130.6; Cl2 (g) = 223.0; HCl (g) = 186.8
a.
b.
c.
d.
e.
14.
1.5 x 10-4 M
1.5 x 10-5 M
7.2 x 10-3 M
7.2 x 10-4 M
none of these
For which of the following changes is ΔSºsys negative?
a.
b.
c.
d.
e.
13.
Na2CO3
KCl
NaNO3
KI
NH4Cl
What is the solubility of BaF2 (s) in a 0.10 M solution of NaF? (Ksp of BaF2 (s) = 1.5 x
10-6).
a.
b.
c.
d.
e.
12.
cannot be determined without the temperature
yes
no
only if ΔSuniv < 0
only if ΔSuniv = 0
Addition of which of the following salts is most likely to decrease the solubility of MgCO3
in water?
a.
b.
c.
d.
e.
11.
1.18
7.00
1.00
0.88
none of these
20.0 J/K
-84 J/K
none of these
154 J/K
-166.8 J/K
At the equivalence point of the titration of a 0.15 M NH3 solution with 0.15 M HCl
solution, the pH will be:
a.
b.
c.
d.
e.
less than 7.00
7.00
greater than 7.00
cannot be determined
none of these
15.
Predict the sign of ΔSºrxn for the following reaction:
H2 (g) + 2 O3 (g) → 2 O2 (g) + H2O2 (l)
a.
negative
b.
positive
c.
zero
d.
cannot be predicted
e.
depends on ΔHºrxn
16.
Which of the following acids is best suited for preparing a buffer solution with pH = 5.00
and a high buffer capacity: C6H5COOH, HNO2, HClO, CH3CH2COOH?
a.
CH3CH2COOH
b.
C6H5COOH
c.
cannot be determined
d.
HClO
e.
HNO2
17.
Calculate ΔSº for the reaction between NO2 (g) and H2 (g) to give one mole of N2 (g) and
the correct number of moles of H2O (g). Sº values (J/mol.K): NO2 (g) = 240.0, H2 (g) =
130.7, N2 (g) = 191.6, H2O (g) = 188.8.
a.
-56 J/K
b.
+9.7 J/K
c.
-9.7 J/K
d.
-28.6 J/K
e.
none of these
18.
What is the pH of a 0.40 M solution of sodium acetate (Na+CH3COO-)?
a.
9.18
b.
4.82
c.
7.88
d.
11.23
e.
none of these
19.
A particular reaction is non-spontaneous, and has ΔSºrxn > 0. Which of the following
statements must be true?
a.
ΔHºrxn > 0
b.
ΔHºrxn < 0
c.
ΔSºsurr > 0
d.
ΔSºuniv > 0
e.
none of these
20.
Which of the following salts is most soluble in water at 20 ºC? CaSO4 (Ksp = 2.4 x 10-5);
BaSO4 (Ksp = 1.1 x 10-10); PbSO4 (1.6 x 10-8).
a.
CaSO4
b.
PbSO4
c.
cannot be determined
d.
they are all equally soluble
e.
BaSO4
21.
What is the pH of a solution that is 0.050 M in NH3 (aq) and 0.060 M in NH4+ (aq)?
a.
9.17
b.
none of these
c.
9.33
d.
9.43
e.
9.25
22.
A buffer solution is prepared containing equal concentrations of CH3COOH (aq) and
CH3COO- (aq). What is the pH of this solution?
a.
none of the other answers
b.
4.98
c.
1.30
d.
2.00
e.
3.70
23.
Which of the following substances will have the greatest molar entropy?
a.
C2H5OH (g)
b.
CH4 (g)
c.
CH3COOH (l)
d.
CH3OH (l)
e.
CH3CHO (g)
24.
Consider two buffer solutions A and B: A contains 0.25 M NH3(aq) and 0.25 M
NH4+(aq). B contains 0.34 M NH3(aq) and 0.34 M NH4+(aq). Which of the following
statements is true?
a.
b.
c.
d.
e.
The pH of both solutions is the same, but buffer B has a higher buffer capacity than
A.
Buffer A has a lower pH and lower buffer capacity than B.
Buffer A has a lower pH and higher buffer capacity than B.
The pH of both solutions is the same, but buffer A has a higher buffer capacity than
B.
Buffer A has a higher pH and a higher buffer capacity than B.
25.
Calculate ΔSº for the reaction: 2 N2O5 (g) → 4 NO2 (g) + O2 (g)
Sº values (J/mol.K): N2O5 (g) = 346, NO2 (g) = 239.9, O2 (g) = 205.0
a.
473 J/K
b.
-246 J/K
c.
819 J/K
d.
299 J/K
e.
99 J/K
26.
Which of the following salts will give an acidic solution when dissolved in water?
a.
FeBr3
b.
NaF
c.
K2CO3
d.
CaBr2
e.
none of these
27.
Which of the following will increase the solubility of AgBr (s)?
a.
addition of NH3 (aq)
b.
addition of HBr
c.
addition of AgNO3 (s) (a very soluble salt)
d.
addition of NaNO3 (a very soluble salt)
e.
none of these
28.
Which of the following salts will give a basic solution when dissolved in water?
a.
none of these
b.
NH4Br
c.
NaI
d.
KNO3
e.
KClO4
29.
What is the final pH after 10.0 mL of 0.200 M NaOH are added to a 50.0 mL solution of
0.400 M CH3COOH?
a.
3.78
b.
4.12
c.
4.42
d.
2.49
e.
4.87
30.
Calculate the Ksp at 25 ºC of a salt MX2 whose solubility is 3.2 x 10-4 M.
a.
1.3 x 10-10
b.
3.3 x 10-11
c.
6.5 x 10-11
d.
2.1 x 10-7
e.
none of these
Useful Information: Acid Ka values
Equations
-----------------------------------------------------------------------------------------------------------------HIO3
1.6 x 10-1
pH = -log[H3O+]
-2
HClO2
1.12 x 10
KW = [H3O+][OH-] = 1.0 x 10-14 (at 25oC)
HNO2
7.1 x 10-4
HF
6.8 x 10-4
pH = pKa + log([base]/[acid])
-4
HCOOH
1.8 x 10
C6H5COOH
6.3 x 10-5
CH3COOH
1.8 x 10-5
CH3CH2COOH 1.3 x 10-5
HClO
2.9 x 10-8
HBrO
2.3 x 10-9
HCN
6.2 x 10-10
HIO
2.3 x 10-11
Kb Values
-------------------------------NH3
1.76 x 10-3