Chern 201
Spring
Fall 2010
1. EXAM 2 - FORM A
What is the
Ksp
page 1
expression for iron(lI) hydroxide?
(a) [Fe2+]2[OH-]
B:Fe"HOH-l'
(b) [Fe2+][02-]
(c) [Fe3+][OH-]3
(eJ [Fe3']2[0'-]'
(ab) [Fe3+][02-]
- Kp :o[Fe~+l [ O/el l
2. What is the molar solubility of iron(II) hydroxide in pure water?
4.87x1O- 17
(b) LOx 10- 10 M
@2.3X1O- 6 M
(a) 7.0xlW 9 M
(d) 8.9xlO- 14 M
fe~(-i) 2
t:Sf
3. 4s?:>
t S-
S
)
oY
Ksp
of iron (II) hydroxide
(c) 3.7xlO-5 M
AX 2
~~ ~; -::: i;re­
4.8:j,,(jl
.......
'"'-
4
-(
2. s' io Ii
What will happen if HCI is added to a saturated aqueous solution of iron(lI) hydroxide in water?
("Saturated solution" means that there is solid iron (II) hydroxide present and the system is at
equilibrium.)
(a) The iron(II) hydroxide solubility equilibrium shifts to the LEFT and more solid iron(II)
hydroxide dissolves.
(c) The iron(ID hydroxide solubility equilibrium shifts to the LEFT and more iron(lI) hydroxide
precipitates out of solution.
(b) The iron(II) hydroxide solubility equilibrium shifts to the RIGHT and more iron (II) hydroxide
eciPitates out of solution.
(d) The iron(II) hydroxide solubility equilibrium shifts to the RIGHT and more solid iron(ID
ydroxide dissolves.
I(
-1- ~ LL
je) Nothing happens.
eG: <;:
fl
etrl.A 1 - S" IP.s.
~
He (
~-do(-f) ~ ~~i"fPU- ,
4. t 'f . 0
r
1-\~O+t 0 t-{ - ~ 2 J-h....
Alum~~ ion forms a cothplex ion WIth 6 fluoride ions. What is the Kf expression for the
formation this complex ion?
(a) ®
[AIF/+]
[AP+]6[F]
(b)
[AI 3+][FJ6
[AIFi+]
[AIFtJ lAI 3+][F-]6 (e)
[AIF6]
[AI][F6J
Al 1 -r +- 6 F-
<~
At F6
3­
(c) [A1 3+][FJ6
">
Chern 201
EXAM2
FORMA
page 2
Spring 2010
Fall
5. What is the minimum amount of sodium phosphate that would need to be added to 5.00 L of a
1.00xlO- 3 M solution of silver nitrate to cause silver phosphate to precipitate out of solution?
Ksp of silver phosphate = 8.89xlO- 17
("A" question)
Cfa))ust above 7.29xlO- 5 g
(d)Just above 0.733 g
(b) just above 2.91xlO- 2 g
(e) just above 0.582 g (c) just above 1.81 g PO"
+
3;
Na-Alt}
[A,+J ,/?otJ
KSf';::
yz-,4
\ J> 4 »
t
2:TC\'
~;;:
6.
~
(c)
(d) 7. The total energy of the universe is constant. The total entropy of the universe is constant. The total energy of the universe is increasing with time.
The total entropy of the universe is decreasing with time.
Imagine that you have 6 gas molecules distributed between 2 connected containers as shown
below. Which one of the two states has the HIGHEST entropy? Why?
eJ
00
0
00
0
State 1 (a) (b) (f!)
(d) State 1 has
molecules.
State 1 has
State 2 has
molecules.
State 2 has
()
(d
0
0
0
State 2
the highest entropy because it represents a more probable distribution of the
the highest entropy because it represents a more ordered state.
the highest entropy because it represents a more probable distribution of the
the highest entropy because it represents a more ordered state.
Chern 201
Fall 2010
Spring
8. EXAM 2 - FORM A
page 3
Calculate i\S a for the following reaction:
=
=
=
SO of CH4(g) 186.1 J/(K'mol); So ofH2S(g) 205.6J/(K-mol); So ofH2S(aq) 122
J/(K-mol); S a of CS 2(g) 237.8 J/(K-mol); So of CS 2(l) 151 J/(K-mol); So of H2(g) 130.6
J/(K'mol)
=
(a) 162.9 J/(K-mol)
(d) 233.0 J/(K-mol)
=
=
(c) -233.0 J/(K-mol)
(ab) 368.4 J/(K-mol)
@162.9 J/(K-mol)
(e) - 368.4 J/(K-mol)
t1~ ~ S~S2- + 45~l- - 2S~~}
.z 3>=1. 2 + 4 9.
I ~O.,
-
Z· liJ'::l.' -
(86. f
What is i\Go at 25°C for a reaction with i\Ho
(a) -62 kJ/mol
'Qe) 24.5 kJ/moI
J
(b) 24.5 kJ/mol
(ab) -128 kJ/mol
T
4
s:O
=
50.0 kJ/mol and i\So
(c) 62.0 kJ/mol
:=
(d) 128 kJ/mol
-s-o..J+.2 9 g(.......
25:0
1000
- + 2-'1, S-
10. = -250. J/(K'mol)?
kJI
J-1O
Which one of the following statements would be true for the reaction in the preceding question?
(a) (b) @
(d) This reaction is favorable (spontaneous) at all temperatures.
This reaction is unfavorable (non-spontaneous) at all temperature.
This reaction is favorable (spontaneous) at low temperatures, but unfavorable (non­
spontaneous) at higher temperatures.
This reaction is favorable (spontaneous) at high temperatures, but unfavorable (non­
spontaneous) at lower temperatures.
Chern 201
Fall 2010
Spring
EXAM2
FORMA
page 4
How is an aqueous solution of ethyl ammonium chloride, [CH3CH2NH 3 ]Cl, best characterized?
11.
SOIUtiOn of a strong acid
(c 1 olution of a weak acid
e) neutral solution
(b) solution of a strong base (d) solution of a weak base (ab) buffer solution i
ttc. (-
S. 't..--­
What is the pH of a 0.25 M aqueous solution of [CH3CH 2NH 3]CI?
12.
(c) 8.72
(e) 8.32
(d) 0.60
Cff3
c)f2
_ k "'"
NH2.
-K(
(O" vJeR l ",-~ol~
,f C~A >'). k
pH::: -~
[1-(1::
I~~,?:$ ZL/~~t6iJ
13.
What is the pH of an aqueous mixture of 0.10 M [CH3CH2NH 3]CI and 0.85 M CH 3CH2NH2 ?
(b) 10.52
vJ
f
i..sc
\-I -=
(c) 9.81
..........I ;+15 S.J+
b
1
::
(b) 4.18
1<d)11.67~]
f~
~~V-
~A + -bi [Ctf3 C'\''h. NlfJ
lo,"1~~L
_ ::
\I C (..Hjct( Nf-f + J
1
+
O_~2-~'(
"Ii"
(e) 3.03
"> H H ~t....:Ao,,p
~f~ _~
,~. b ·ID
II, n:f(
.j,
t.
'~III{,iJ
(J
O.l?.>'"
O~ 10
Chern 201
Spring
Fall 2010
14. EXAM 2 - FORM A
page 5
What buffer component ratio would be needed to make a pH 4.75 buffer with benzoic acid,
C6HsC02H, and sodium benzoate, Na[C 6HsC02]?
B
(b) 0.28
(e) 1.6
HH er·--hp·~
[C,Hi 090 -)
(d) 0.63
r~ ~
\0
CC. He U>ol-0
1>+1 -
(e) 1.0
tk<t +
~t~~H::U~
pktt
I
:=
~
15. How much solid Na[C6HsC02] (mw = 145.11 g/mol) would need to be added to 250. mL of a
C6HsC02H solution to make a pH 4.75 buffer?
~.I,9..M
C~ (a) 2.3 g
(b) 0.18 g
-tv ~ pve
VtO " So
(c) 0.067g
flfq)
CCb KsCoo-J
[~HsWOI-/J
rYI
::>
(d) 4.9 g
e~ :
few- V
C~V
L~
~
=--
_ -
~
=- ~.>'1
C·V Mw.
= l.S'l· C:YM~-::-~ ~~~
~~,. .:3,9Hl.IM· o. 2.51: l!i~.11 : : 12. f If -:::. /33
16. The pH of an aqueous H3P04 solution is adjusted to pH 5 by addition of strong base. Which of
the following would be the primary species in solution at this pH?
Chern 201
Spring 2010
EXAM 2 - FORM A
page 6
Consider the following titration for the next 4 questions.
50.0 mL of 0.150 M NaOH(aq) (in flask) is titrated with 0.100 M HBr(aq) (in buret).
17. What is the overall reaction occurring in the titration?
(a) HBr(aq) +
NaOH(aq» .... NaH(aq) + BrOH(aq) NaOH(aq) .... Nat(aq) + OH-(aq) (c) HBr(aq) + NaOH(aq) .... H20(l) + NaBr(aq)
d) 2HBr(aq) + H20(1) .... H30t(aq) + Brz<aq)
(e) Nat(aq) + Br-(aq)"" NaBr(aq)
~
18. How many mLls of the HBr solution need to be added to reach the equivalence point of the
titration?
(a) 50.0 mL ~5.0 mL
Cf
(d) 40.0 mL
(e) 100. mL
VI -=- C l..
V =-
C,
'2.­
'Z-
19. V.. .
~ ~
(c) 30.0 mL
() ,Qt. SOMI:.. ?"S""""""'( Ow\M
aft~
Which of the following are present in the flask
of the HBr(aq) solution have been
added? Mark all correct answers. (Be sure to c~ur answer to the abpve. question in
answering this question.)
D '1-5 - Q -He
~
g >
(a) Brz<aq)
~HBr(aq)
20. (d) NaH(aq) What is the pH of the solution in the flask after 80.0 mL of the HBr(aq) have been added?
(a) 3.77
ro~
\.VeA'€
t;;D + 8~ -- ,
t \--\ t
]
(c) 1.21
(b) 12.79
p;. d- <v.f
~\~
\""'-
~aBr(aq)
(b) NaOH(aq)
(ab) BrOH(aq) r
;
(d) 2.41
(e) 11.58
~ ......... \,JfL
()~
~ [ Hr.,-r J
F\-\ :O',{,O >~ ,lOS ~ [
C~
s-
lo'\..­
))
- V
2.. 'l \ ]
~~f .. O.1M
~O ~ t -+ 8&1 f\1
,
_
_pol;:;r­
ADDITIONAL INFORMATION and EQUATIONS
Some Ka Values at 25°C
1.8 xlO- 5
C6HsC02H
6.3 xlO- 5
H 3B03
5.8 xlO
H 2C03
4.3
H 2C20 4
5.6 xlO-z
lO
X 10- 7
5.6 xlO- 11
HC02H
7.5 xlO- 3
6.2 xlO- 8
very large
1.2 xlO- 2
4.8 xlO
3.5 xlO- 4
HF
Some Kb values at 25°C
Kb
NH3
1.8 xlO- 5
CH3NHz
4.4 xlO- 4
CH 3CH 2 NH2
5.6 x104
CSH 5N
1.7 xlO- 9
pH
=
[base]
pK + log..!:------"­
a
[acidJ
R = 8.314xlO- 3 kJ/(mol'K)
0° C =273.15 K
13