079 Version Make up 1 laude (51635)
This print-out should have 30 questions.
Multiple-choice questions may continue on
the next column or page nd all choices
before answering.
Constants R = 8.314 JK1 mol1
[C]c[D]d
[A]a [B]b
G H TS
Q
Denitions
Kw [H+ ][OH ]
pH log [H+ ]
pOH log [OH ]
Equations
G = H T S
Hvap 1
1
P2
=
ln
P1
R
T1 T2
= M RT
Tb = iKb m
Tf = iKf m
Pi = Pi i
P=
Pi
i
q = mcT
q = mH
G = RT ln K
G
RT
K=e
K2
H 1
1
ln
=
K1
R
T1 T2
Q = K [at equil.]
[H+ ] = (Ka Ca )1/2
[OH ] = (Kb Cb )1/2
[H+ ] = Ka (Ca /Cb )
pH = pKa + log(Cb /Ca )
[OH ] = Kb (Cb /Ca )
pOH = pKb + log(Ca /Cb )
001 6.0 points
Rank following bases from most to least basic:
ammonia (NH3 )
pKb = 4.74
aniline (C6 H5 NH2 )
pKb = 9.42
pyridine (C5 H5 N)
pKb = 8.77
methylamine (CH3 NH2 )
1
pKb = 3.34
1. NH3 > C5 H5 N > C6 H5 NH2 > CH3 NH2
2. C6 H5 NH2 > CH3 NH2 > NH3 > C5 H5 N
3. C5 H5 N > C6 H5 NH2 > CH3 NH2 > NH3
4. CH3 NH2 > NH3 > C5 H5 N > C6 H5 NH2
correct
Explanation:
The value of pKb is inversely proportional
to the basicity (strength) of the base. By
ranking from the smallest (3.34) to the smallest (9.42) pKb , one is ranking from the most
to least basic.
002 6.0 points
Which of the following phase changes is not
correctly paired with the sign of its change in
enthalpy?
1. vaporization, H is +
2. deposition, H is + correct
3. freezing, H is 4. condensation, H is 5. melting, H is +
Explanation:
Deposition is an exothermic phase change
and H is negative.
003 6.0 points
Assuming you have a pure sample of water, in
which answer choice are all values of Kw correctly paired with their corresponding value
of [H+ ]?
A) Kw = 1.33 1015
B) Kw = 1.46 1014
C) Kw = 1.38 1013
1) [H+ ] = 1.21 107
2) [H+ ] = 3.65 108
3) [H+ ] = 3.71 107
1. A1, B2, C3
Version 079 Make up 1 laude (51635)
2
2. A3, B2, C1
1. CH3 F < (CH3 )2 NH < CBr4 < CH3 Cl
3. A2, B3, C1
2. CH3 Cl < CH3 F < (CH3 )2 NH < CBr4
4. A3, B1, C2
3. (CH3 )2 NH < CBr4 < CH3 Cl < CH3 F
5. A2, B1, C3 correct
4. CBr4 < CH3 Cl < CH3 F < (CH3 )2 NH
correct
6. A1, B3, C2
Explanation:
According the axiom that like dissolves
like, the least miscible will be the non-polar
molecule CBr4 . The most miscible will be
(CH3 )2 NH, which exhibits hydrogen bonding
just as water does. Between the two polar
molecules, CH3 F is the more polar and thus
the more miscible because of the greater electronegativity dierence.
Explanation:
The proton concentration in a sample of
pure water is directly proportional to Kw .
004 6.0 points
30.2 g of glycerine (C3 H8 O3 , with MW
92.1 g/mol) are dissolved in 150 g of water. What is the boiling point of the solution?
(Kb of water = 0.515 C/m )
006 6.0 points
In the derivation of the Clausius-Clapeyron
equation, the Svap term is present in early
steps but isnt present in the nal equation.
Why is this?
1. 0.104C
2. 100.10C
3. 101.13C correct
1. We assume that Svap is independent of
temperature and are able to ignore it.
4. 1.13 C
5. 101.52C
Explanation:
mglyc = 30.2 g
mwater =150 g
2. The Svap term actually is present in the
nal equation.
MWglyc = 92.1 g/mol
Kb = 0.515 C/m
Tb = Kb m
mol glycerol
= Kb
kg water
30.2
mol C3 H8 O3
= (0.515C/m) 92.1
0.150 kg water
= 1.13C
0
Tb = Tb + Tb = 101.13C
005
6.0 points
Rank the following liquids in increasing
order of solubility in water (H2 O): CH3 F,
(CH3)2 NH, CH3 Cl, CBr4 .
3. We assume that Svap = Svap , and we
are able to eliminate the term altogether.
4. We assume ideal behavior for the gas, and
the Svap term reduces to a constant and is
eliminated. correct
Explanation:
Because we assume that the gas behaves
ideally, Svap is the same regardless of the
gas in question, and taking its base e exponent results in constant which can be readily
eliminated.
007
6.0 points
Consider the reaction,
A(aq ) + B(aq ) C(aq )
Version 079 Make up 1 laude (51635)
The equilibrium constant, K , is 2. If the
concentrations of A, B and C are 2 M, 2 M
and 10 M, respectively, which of the following
would occur?
2. K1 = 10, K2 = 100
3. K1 = 100, K2 = 10
4. K1 = 10300 , K2 = 1 correct
1. not enough information
2. nothing would occur
3. the reaction would move right
4. the reaction would move left correct
Explanation:
[C]
10
Q=
=
= 2. 5
[A] [B]
22
Since Q > K , the reaction would move
right.
008 6.0 points
What would be molar solubility of a very expensive salt, awesomium, which is composed
of 3 cations and 2 anion (X3 Y2 ) and whose
Ksp is 1.08 1018 ?
1. 1 109 M
Explanation:
Since the reaction is exothermic, the value
of K should be inversely proportional to T . So
the higher temperature must have the smaller
value of K . This eliminates two of the answer choices. Since H = 5, 500 kJ mol1
is a very large number, it also means that
dramatic changes in K are expected in response to changes in T , eliminating two answer choices, and leaving only one that satises both criteria.
010 6.0 points
Consider the reaction below:
2NH3 (g) 3H2 (g) + N2 (g)
If K is 1080 which of the following is a
good estimate of equilibrium concentrations
of NH3 , H2 and N2 , respectively?
1. 5 M, 0 M and 0 M, respectively correct
2. 0.0001 M correct
2. 0 M, 15 M and 5 M, respectively
3. 1 M
3. 5 M, 7.5 M and 2.5 M, respectively
4. 6.1 107 M
4. 1 M, 9 M and 4.5 M, respectively
Explanation:
For a salt of the form X3 Y2
molar solubility = x =
x=
3
1.08 1018
27 4
009
Ksp
27 4
0.2
0.2
Explanation:
The magnitude of K is suciently small
that we can infer that none of the reactants
will convert into products.
= 0.0001 M
6.0 points
The combustion of octane has a
standard change in enthalpy, H =
5, 500 kJ mol1. If the reaction were performed at T1 = 200 K and T2 = 300 K, which
pair of equilibrium constants might be correct?
1. K1 = 1, K2 = 10300
011 6.0 points
An animal cell assumes its normal volume
when it is placed in a solution with a total
solute molarity of 0.3 M. If the cell is placed
in a solution with a total solute molarity of
0.1 M,
1. water enters the cell, causing expansion.
correct
2. no movement of water takes place.
Version 079 Make up 1 laude (51635)
3. the escaping tendency of water in the cell
increases.
4. water leaves the cell, causing contraction.
Explanation:
012 6.0 points
What would be the pOH of a solution of
Sr(OH)2 (strontium hydroxide) prepared by
dissolving 122 g of the base into 10 L of pure
water (H2 O)?
1. 0.7 correct
4
5. 1164 torr
Explanation:
Ptotal = a Pa + b Pb + ...
Ptotal = 0.25 1515 torr + 0.75 38 torr
Ptotal = 407 torr
014 6.0 points
Which of the following is a possible combination of values for Hlattice , Hhydration and
Hsolution , respectively, for a salt whose dissolution is exothermic.
1. +380, 351, and 29 kJ mol1
2. 260, 278, and 18 kJ mol1
2. 13
3. +302, 274, and 28 kJ mol1
3. 1
4. +461, 465, and 4 kJ mol1 correct
4. 13.3
Explanation:
1 mol
= 1 mol Sr(OH)2
122 g Sr(OH)2
122 g
1 mol Sr(OH)2
= 0.1 M Sr(OH)2
10 L H2 O
Explanation:
Hsolution = Hlattice + Hhydration - the
problem stipulates that Hsolution be negative (exothermic) and this limits the values
the other two terms can have.
015
Sr(OH)2 (aq) Sr2+ (aq) + 2 OH (aq)
[OH ] = Cb 2 = 0.1M 2 = 0.2M
pOH = log[OH ] = log(0.2) = 0.7
013 6.0 points
If ammonia has a pure vapor pressure of
1515 torr and propanol has a pure vapor pressure of 38 torr, a mixture of 6 moles of ammonia and 18 moles of propanol would have
what total vapor pressure?
1. 1145 torr
2. 776 torr
Write the equilibrium expression for the following reaction:
2 N O (aq ) + 4 H2 O( )
3 H2 (aq ) + 2 H + (aq ) + 2 N O3 (aq )
1. K =
[ H 2 ] 3 [ H + ] 2 [ N O3 ] 2
correct
[N O ]2
2. K =
[N O ]2
[ H 2 ] 3 [ H + ] 2 [ N O3 ] 2
[[H + ]2 [N O3 ]2
3. =
[N K O ]2
4. K =
[N O ]2
[ H + ] 2 [ N O3 ] 2
5. K =
[ H 2 ] 3 [ H + ] 2 [ N O3 ] 2
[ N O ] 2 [ H2 O ] 4
3. 388 torr
4. 407 torr correct
6.0 points
Version 079 Make up 1 laude (51635)
Explanation:
Set up K , products in the numerator, reactants in the denominator, all raised to respective stoichiometric coecients.
016 6.0 points
Consider the following exothermic reaction:
CaO(s) + CO2 (g ) CaCO3 (s)
In response to a decrease in temperature, the
system would:
5
018 6.0 points
What would be the pH of a 0.563 M solution of
ammonia (NH3) at room temperature? The
Kb of ammonia is 1.78 105 .
1. 9
2. 2.5
3. 11.5 correct
1. shift right correct
4. 4.5
2. not enough information
5. 7
3. shift left
Explanation:
[OH ] = (Kb Cb )1/2 = (1.78 105 0.563)1/2
4. not change
= (105 )1/2 = 102.5
Explanation:
Decreasing the temperature of an exothermic reaction can, according to the Le Chatelier principle, be thought of as removing some
of the products (on the right) and the system
would respond by shifting right.
017
6.0 points
If 100 mL of 0.2 M CHOOH and 400 mL
of 0.5 M NaCHOO are mixed, what is the pH
of the resulting solution? Assume the pKa of
formic acid is 3.7.
1. 2.2
pOH = log[OH ] = log(102.5 ) = 2.5
pH = pKw pOH = 14 2.5 = 11.5
019 6.0 points
Which of the following is a restatement of
Henrys Law?
1. A mixture of two liquids will have a vapor
pressure that isnt equal to either of the pure
liquids vapor pressures.
2. Heating a solution will decrease the solubility of gases dissolved in it.
2. 4.1
3. 3.7
4. 5.1
5. 4.7 correct
Explanation:
pH = pKa + log [A ]/[HA]
= 3.7 + log (0.4/0.04)
= 3.7 + log (10)
= 3. 7 + 1
= 4. 7
3. Adding a non-volatile solute to a liquid
will lower its vapor pressure.
4. As the partial pressure of a gas above a
liquid increases, the gass solubility in that
liquid also increases. correct
Explanation:
Henrys law, formulated by William Henry
is 1803 states: At a constant temperature,
the amount of a given gas dissolved in a given
type and volume of liquid is directly proportional to the partial pressure of that gas in
equilibrium with that liquid.
Version 079 Make up 1 laude (51635)
6
020 6.0 points
Consider the reaction below:
3. x and z
CaS(aq) + MgSO4 (aq) CaSO4 (s) + MgS(aq)
4. y and x
If K is 20 and the initial concentrations
of CaS, MgSO4 and MgS are 4.5 M, 4.4 M
and 0 M respectively, what is the equilibrium
concentration of MgSO4 ?
5. x and y correct
6. z and y
7. z and x
1. 4 M
Explanation:
Sublimation/deposition occurs at the
solid-gas phase boundary, and vaporization/condensation occurs at the liquid-gas
phase boundary
2. 0.5 M
3. 0.4 M correct
4. 0 M
022 6.0 points
How many phase transitions occur by following the steps described below?
step 1: At 900 K going from 20 atm to 50 atm
step 2: At 50 atm going from 900 K to 550 K
step 3: At 550 K going from 50 atm to 75 atm
Explanation:
I
MgSO4 CaSO4 MgS
4. 5 M 4. 4 M
C -4 M
0M
-4 M
4M
E 0. 5 M 0. 4 M
100
4M
021 6.0 points
Which line segments (x, y and z ) correspond to sublimation/deposition and vaporization/condensation, respectively?
Carbon Dioxide
4
10
80
Pressure, atm
R CaS
60
40
Pressure, bar
20
10
3
10
2
z
0
0
200 400 600 800 1000
Temperature, K
y
101
10
0
200
1. 3 phase boundaries are crossed
x
250
300
350
Temperature, K
1. y and z
400
2. 1 phase boundaries are crossed correct
3. 2 phase boundaries are crossed
4. 0 phase boundaries are crossed
Explanation:
2. not enough information
Version 079 Make up 1 laude (51635)
023
7
6.0 points
1. I, II, III
2. II only correct
3. I only
Molar Gibbs energy, Gm
025
Which of the following statements is/are
true concerning Kw and temperature (T)?
I) Kw gets larger as T decreases
II) Kw = 1014 for water at T = 298 K
III) Kw [OH ] = [H+ ] for water at any T
6.0 points
pure liquid
solid
solvent
Temperature, T
4. III only
5. I, III
6. II, III
7. I, II
Explanation:
All equilibrium processes are temperature
dependent, and because auto-protolysis is endothermic, Kw increases as temperature increase. Kw = [H + ][OH ].
024 6.0 points
For a solution with an [OH ] of 1010 M,
what would be the value of [H+ ] , pH and
pOH, respectively?
1. 1014 M, 4, 10
2. 104 M,
10, 4
3. 104 M,
4, 10 correct
4. 1014 M, 10, 4
5. 104 M,
6. 104 M,
4, 14
4, 10
Explanation:
1014
1014
[H+ ] =
= 10 = 104
[OH ]
10
+
pH = log10 ([H ])
pOH = log10 ([OH ]) = 14 pH
Referring to the graph above, and using
your knowledge of Hsolution , complete the
following statement concerning freezing point
depression:
The molar (enthalpy/entropy) of a pure
liquid is always (greater/less) than that of
a dilute solution. This lowers the value of
Gm for the solvent at all temperatures, thus
lowering the freezing point.
1. enthalpy; less
2. enthalpy; greater
3. entropy; less correct
4. entropy; greater
Explanation:
G = H T S , so in order to decrease G at a
given temperature, we have to either decrease
H or increase S . We know the Hsolution can
be positive or negative depending on the solute, but colligative properties dont depend
on the identity of the solute, so the eect on
the enthalpy is not a good explanation. We
also know that mixtures always have more entropy than pure substances, so that must be
the best explanation.
026 6.0 points
What would be the pH of a solution of hypoiodous acid (HOI) prepared by dissolving
Version 079 Make up 1 laude (51635)
144 grams of the acid in 200 mL of pure water
(H2 O)? The Ka of hypoiodous acid is 2 1011
8
is (spontaneous / nonspontaneous) and K is
(less / greater) than one.
1. 5 correct
1. nonspontaneous; less correct
2. 10
2. spontaneous, less
3. 7
3. nonspontaneous; greater
4. 13
4. None of these; G is not directly related
to K .
5. 1
5. spontaneous, greater
Explanation:
144 g HOI
1 mol
= 1 mol HOI
144 g
1 mol HOI
= 5 M HOI
0. 2 L H 2 O
[H+ ] = (Ka Ca )1/2 = (2 1011 5)1/2
= (1010 )1/2 = 105
pH = log[H+ ] = log(105 ) = 5
027 6.0 points
Rank the following salts from greatest to least
molar solubility:
A) AgI Ksp = 8.52 1017
B) ZnF Ksp = 0.0304
C) PbSO4 Ksp = 2.53 108
D) CsClO4 Ksp = 0.00395
Explanation:
A positive G (standard reaction free
rxn
energy) denotes an endothermic reation,
which is nonspontaneous. Also, G =
rxn
R T ln K , so a positive G would result
rxn
in a K that is between the values of zero and
one.
029 6.0 points
The specic heat of water is 1.00 cal/g C, the
heat of vaporization of water is 540 cal/g, and
the heat of fusion of water is 80 cal/g. How
much heat would be required to convert 10
grams of ice at 0 C to 10 grams of water at
75 C?
1. 61.5 kcal
2. 15.5 cal
1. B > D > C > A correct
3. 1.55 kcal correct
2. D > B > C > A
4. 155 cal
3. D > C > B > A
5. 6150 cal
4. B > D > A > C
Explanation:
All of the salts are composed of a single
cation and anion, so the solubility of each is
the square root of its Ksp .
If
G
rxn
028 6.0 points
is positive, then the forward reaction
Explanation:
10 g
step 1 10 g step 2 10 g
H2 O(s) H2 O( ) H2 O( )
0 C
0 C
75 C
80 cal
Step 1:
(10 g) = 800 cal
g
1 cal
Step 2:
(10 g)(75 0) C = 750 cal
g C
Version 079 Make up 1 laude (51635)
Total = 800 cal + 750 cal
= 1550 cal
= 1.55 kcal
030 6.0 points
Consider two closed containers. Container
X is a 2 L container that contains 0.5 L of
acetone. Container Y is a 3 L container that
contains 1.8 L of acetone. Both containers and
contents are at 28 C. Which of the following
is true?
1. The vapor pressure in container X is
greater.
2. The vapor pressure in container Y is
greater.
3. The vapor pressures in both containers
are equal. correct
4. You would need information about the
shape of the containers to be able to answer
this question.
Explanation:
9