Transcript Slide 1

Revision for second Midterm
Dr. Ali Bumajdad
1- When a system ________ , E is always negative.
A)
B)
C)
D)
E)
absorbs heat and does work.
gives off heat and does work.
absorbs heat and has work done on it.
gives off heat and has work done on it.
none of these is always negative.
2- Using the following data:
C(s) + H2O(g)  CO(g) + H2(g)
CO(g) + H2O(g)  CO2(g) + H2(g)
CO(g) + 3H2(g)  CH4(g) + H2O(g)
H0 = +131.3 kJ
H0 = -41.2 kJ
H0 = -206.1 kJ
Calculate the heat of reaction for the coal gasification process:
2C(s) + 2H2O(g)  CH4(g) + CO2(g)
A)
B)
C)
D)
E)
3-
+15.3 kJ
378.6 kJ
-116.0 kJ
-378.6 kJ
-157.2 kJ
A 1.80 g sample of octane, C8H18, was burned in a bomb calorimeter
whose total heat capacity is 11.66 kJ/0C. The temperature of the
calorimeter plus its contents increased from 21.360C to 28.780C. What
is the heat of combustion (kJ/g) of octane?
A)
B)
C)
D)
E)
+48.1
+48.5
–48.1
–84.1
+84.1
3-
The vapor pressure of pure water at 250C is 23.8 torr. What is the vapor
pressure (torr) of water above a solution prepared by dissolving 18 g of a
nonelectrolyte, (MW = 180 g/mol) in 95 g of water?
A)
B)
C)
D)
E)
4-
An aqueous solution of sodium carbonate was prepared containing
14.0% Na2CO3 by weight. What is the mole fraction of Na2CO3 in this
solution?
A)
B)
C)
D)
E)
5-
24.3
23.4
0.451
0.443
23.8
0.0724
1.724
0.167
0.0269
3.24
The phrase “like dissolves like” refers to the fact that _______:
A)
B)
C)
D)
E)
polar solvents dissolve polar solutes and nonpolar solvents dissolve
nonpolar solutes.
solvents can only dissolve solutes of similar molar mass.
condensed phases can only dissolve other condensed phases.
polar solvents dissolve nonpolar solutes and vice versa.
all of these.
7- Which liquid will have the lowest freezing point?
A)
B)
C)
D)
E)
8-
pure water
aq. 0.05 M glucose (C6H12O6)
aq. 0.05 M CoCl2
aq. 0.05 M AlCl3
aq. 0.05 M NaCl
The activation energy of a first-order reaction that has a rate constant of
4.41 x 103 s1 at 351K and rate constant of 9.79 x 102 s1 at 588 K is
______ kJ/mol (R=8.31 J/mol-K).
A)
B)
C)
D)
E)
2.67
2.90
0.0589
22.4
0.450
8-
A compound decomposes according to the first order kinetics with a halflife of 112 days. The compound is found to be at a concentration of
0.106 M after decaying for 25 days. What was the concentration at the
start of the 25 days?
A)
B)
C)
D)
E)
10-
0.0908 M
0.124 M
0.704 M
0.201 M
0.321 M
The rate law of the stoichiometric equation:
A + B  C is
2
rate = K[A] . Which of the following will not increase the rate of
the reaction?
A)
B)
C)
D)
E)
increasing the concentration of reactant A.
increasing the concentration of reactant B.
increasing the temperature of the reaction.
adding a suitable catalyst.
none of these will increase the reaction rate.
11- Initial rate data have been determined at a certain temperature for the
gaseous reaction: 2NO + 2H2  N2 + 2H2O
[NO]0
0.10
0.10
0.20
[H2]0
0.20
0.30
0.20
Initial rate (M/s)
0.0150
0.0225
0.0600
The numerical value of the rate constant is:
A)
B)
C)
D)
E)
7.5
3.0 x 103
380
0.75
3.0 x 104
12- What is the equilibrium expression Keq for the following reaction?
P4(g) + 5 O2 (g)
A)
5
Keq = PO2 - PP4
B)
Keq =
P
P4O10
C)
Keq =
1
5
PP4 .PO2
D)
Keq =
E)
Keq =
P4O10(s)
PP4 .PO10
PP4 .PO52
PP4 .PO52
PP4 .PO
10
13- The equilibrium constant for the reaction, A
Which of the following statement is true?
A)
B)
C)
D)
E)
B is 8.0 x 1016.
at the equilibrium the concentration of B is greater than that of A.
adding a catalyst will increase the value of the equilibrium
constant.
adding more A will increase the value of the equilibrium constant.
at the equilibrium the concentration of A is greater than that of B.
adding a catalyst will increase the equilibrium concentration of B.
14- Given the following equilibria:
H2(g) + I2(g)
2HI(g)
N2(g) + 3H2(g)
2NH3(g) Keq = 1.04 x 104
Keq = 54.0
Determine the value of the equilibrium constant for the reaction:
2NH3(g) + 3I2(g)
A)
B)
C)
D)
E)
1.51 x 109
2.72 x 108
3.87 x 104
6.74 x 104
none of these.
6HI(g) + N2(g)
15- At 4600C, Keq = 85.0 for the reaction:
SO2(g) + NO2(g)
NO(g) + SO3(g)
A mixture of these gases has the following concentrations of the
reactants and products: [SO2] = 0.040 M, [NO2] = 0.50 M,
[NO] = 0.30 M, [SO3] = 0.020 M. Is this system at equilibrium?
If
not, in which direction must the reaction proceed to reach
equilibrium?
A)
B)
C)
D)
E)
at equilibrium and proceeds to the right
at equilibrium and proceeds to the left
not at equilibrium and proceeds to the right.
not at equilibrium and proceeds to the left.
none of these.
16-A system absorbed 55 kJ of heat, and a work equivalent to 40 kJ
was done on it. The changes in the internal energy of the system
is:
A)
B)
C)
D)
E)
15 kJ
-15 kJ
-95 kJ
95 kJ
55 kJ
17-The molar enthalpy of evaporation of water is 44 kJ mol1.
H2O (ℓ)

H2O (g)
The enthalpy change in the evaporation of 1.8 g of water is:
A)
B)
C)
D)
E)
18 kJ
1.8 kJ
44 kJ
4.4 kJ
180 kJ
18-Given the following reactions:
2H2 (g) + O2(g)  2H2O (g) H = -483.6 kJ
3O2 (g)  2O3 (g)
H = +284.6 kJ
The enthalpy, H, for the reaction is:
A)
B)
C)
D)
E)
-199 kJ
199 kJ
-867.7 kJ
-147 kJ
-303.5 kJ
19-Which of the following reactions corresponds to the standard enthalpy
formation, Hf0, of CH3OH (ℓ):
A)
B)
C)
D)
E)
CO (g) + 2H2(g) → CH3OH (ℓ)
C (g) + 2H2(g) + ½ O2 (g) → CH3OH (ℓ)
C (g) + H2O(g) + H2 (g) → CH3OH (ℓ)
CH4 (g) + ½ O2 (g) → CH3OH (ℓ)
C (s, graphite) + 2H2(g) + ½ O2 (g) → CH3OH (ℓ)
20-Calculate the concentration of CO2 in a soft drink after the bottle
is opened and equilibrates at 250C under a CO2 partial pressure of
3.0 x 104 atm. The Henry’s law of constant for CO2 in water at this
temperature is 3.1 x 102 mol/L.atm.
A) 1.0 x 102 M
B) 9.7 x 103 M
C) 3.1 x 102 M
D) 9.3 x 106 M
E) 0.0 M
21-The molality of 13.0% by mass of an aqueous solution of ethanol
(C2H5OH) is:
A)
B)
C)
D)
E)
3.25
2.83
28.2
130
13.0
m
m
m
m
m
22-Which of the following aqueous solution will have the highest boiling point?
A)
B)
C)
D)
E)
0.1 m Na2SO4
0.20 m glucose (C6H12O6)
0.25 m sucrose (C12H22O11)
0.1 m NaCl
0.1 m MgSO4
23-An aqueous solution of a soluble compound (a nonelectrolyte) is prepared
by dissolving 33.2 g of the compound in water to form 250 ml of solution. The
solution has an osmotic pressure of 1.2 atm at 250C. What is the molar mass
of the compound? [R = 0.0821 L.atm/mol.K]
A)
B)
C)
D)
E)
1.0 x 103 g/mol
2.7 x 103 g/mol
2.3 x 102 g/mol
6.8 x 102 g/mol
28 g/mol
24-Which of the following statements is incorrect?
A)
Heterogeneous catalysts are used in automotive catalytic
converters.
B) Adding a catalyst for the reaction will lower the activation energy for
a reaction.
C) In general, as the temperature goes up, reaction rate stays the
same if the reaction is first order.
D) A solution with a solute concentration greater than the solubility is
called supersaturated.
E) Two solutions of identical osmotic pressure are called isotonic.
25-For the reaction A + B → C + D , the following experiments were carried
out:
Exp.
1
2
3
[A] M
0.15
0.15
0.45
[B] M Initial Rate
0.30
0.60
0.30
4.60
4.60
41.4
The rate law for this reaction is:
A)
B)
C)
D)
E)
k [A]2[B]2
k [A]2
k [A][B]2
k [A]2[B]
k [B]2
26-The reaction: CH3NC 
CH3CN
is a first-order reaction. At 230.30C, k = 6.29 x 104 s1. If the initial
concentration of CH3NC is 1.00 x 103 M, the concentration of CH3NC
after 1000 seconds is:
A)
B)
C)
D)
E)
5.33 x 104 M
2.34 x 104 M
1.88 x 103 M
4.27 x 103 M
1.00 x 106 M
27-A particular first-order reaction has a rate constant of 1.35 x 10 2 s−1 at
250C. What is the rate constant, k at 750C if Ea = 85.6 kJ/mol? [R=8.31
J/mol.k]
A)
B)
C)
D)
E)
3.47 x 104 s1
1.36 x 102 s1
670
s1
3.85 x 106 s1
1.93 x 104 s1
28-Which of the following is a wrong statement for a first order reaction?
A  products
A)
B)
C)
D)
E)
Plot of ln [A] vs. time gives a straight line
The order of the reaction is one
The rate constant, k, has units s-1
The half-life time of the reaction is independent of the concentration
of the reactant
The activation energy can be obtained from a plot of ln[A] vs. time
29-The following equilibrium pressure were observed for the Haber
process at 1270C:
[NH3] = 3.1 x 10−2 mol/L
[N2] = 8.5 x 10−1 mol/L
[H2] = 3.1 x 10−3 mol/L
N2(g) + 3H2(g)
2NH3(g)
Calculate the value for the equilibrium constant K at this temperature.
A)
B)
C)
D)
E)
2.6 x 10−5
3.8 x 104
11.8
3.2 x 104
120
30-The equilibrium expression K, for the reaction below is:
4CuO(s) + CH4(g)
CO2(g) + 4Cu(s) + 2H2O(g)
PCH 4
A)
PCO 2 PH2 2O
B)
[Cu ]PCO 2 PH2 2O
[CuO ] 4 PCH 4
PCO 2 PH2 2O
C)
PCH 4
D)
E)
PCO 2 PH2 2O
4
PCuO
PCH 4
4
PCH 4 PCuO
2
PH 2O PCO2
31- From the following reaction:
2KClO3(s)  2KCl(s) + 3O2(g)
H = -89.4 kJ
H for the decomposition of 12.3 g KClO3 is:
A)
B)
C)
D)
E)
+4.48 kJ
-4.48 kJ
-9.48 kJ
+9.48 kJ
-4.58 kJ
32-Calculate the standard enthalpy of formation of solid Mg(OH)2 given
that:
Mg(s) + ½ O2 (g)

MgO(s)
H0 = -601.5
kJ
Mg(OH)2(s)  MgO(s) + H2O()
H2(g) + ½ O2(g)  H2O()
H0 = +37.1 kJ
H0 = -285.8 kJ
A) -924.8 kJ
B) -924.4 kJ
C) +924.4 kJ
D) +924.0 kJ
E) -924.0 kJ
33-A solution is prepared by dissolving 6.00 g of an unknown nonelectrolyte in
enough water to make 1.00 L of solution. The osmotic pressure of this
solution is 0.750 atm at 25.00C. What is the molecular weight (g/mol) of this
unknown solute?
A)
B)
C)
D)
E)
16.4
196
110
30.6
5.12 x 103
34-Concentrated sulfuric acid is 96.0% H2SO4 by weight. What is the molality
of H2SO4?
A)
B)
C)
D)
E)
4.5 x 102 m
5.4 x 102 m
2.4 x 102 m
1.6 x 102 m
3.9 x 103 m
35-Which one of the following substances would be the most soluble in CCl 4?
A)
B)
C)
D)
E)
CH3CH2OH
H2O
NH3
C10H22
NaCl
36-At 1500C, the equilibrium constant for the reaction below is 280:
2 IBr(g)
I2(g) + Br2(g)
Suppose that 0.200 mole of IBr is placed in a closed one-liter reaction
vessel and the reaction was allowed to reach equilibrium, what is the
concentration of I2 at equilibrium?
A)
B)
C)
D)
E)
0.021 M
0.042 M
0.11 M
0.011 M
0.19 M
37-The value of Keq for the following reaction is 2.0 x 1010 at 1000C:
COCl2(g)
CO(g) + Cl2(g)
The value of Keq for the reaction below at 1000C is ________ .
CO(g) + Cl2(g)
COCl2(g)
A) -2.0 x 1010
B) 5.0 x 109
C) 2.0 x 1010
D) -5.0 x 1010
E) 4.0 x 1010
38-The exothermic ammonia synthesis reaction is:
N2(g) + 3H2(g)
2NH3(g)
This reaction was of great importance during World War I. The
conditions of temperature and pressure that produce the maximum
yield of NH3 from this reaction are:
A)
B)
C)
D)
E)
low T, low P
low T, high P
high T, low P
high T, high P
all of the above
39-A 0.010 M NH3 solution was prepared and it was found that the NH3 had
undergone 4.2% ionization. Calculate the Kb for NH3?
A)
B)
C)
D)
E)
1.8 x 105
7.6 x 105
3.4 x 104
4.3 x 104
5.6 x 105
40-What is the pH of a solution that contains 3.98 x 109 M hydroxide
ion?
A)
B)
C)
D)
E)
8.400
5.600
9.000
3.980
7.000
41-What ratio of acetic acid to sodium acetate concentration is
needed to form a buffer whose pH is 5.70? [Ka = 1.8 x 105]
A) 1 : 5
B) 1 : 1
C) 2 : 2
A) 3 : 2
B) 1 : 9
42-The pH of a one-liter solution of a mixture of 0.300 mole acetic acid
HC2H3O2 (Ka = 1.8 x 105) and 0.300 mole sodium acetate is 4.74. What is
the pH of this solution after adding 0.020 mole of sodium hydroxide? (neglect
any volume changes)
A)
B)
C)
D)
E)
4.80
8.40
2.40
7.00
12.1
43-Given the data below for the reaction: yY + zZ  products,
rate law is, rate = ______ :
Expt. No.
[Y]/M
[Z]/M
1
2
3
0.100
0.200
0.100
0.100 M
0.100 M
0.200 M
A)
B)
C)
D)
E)
the
Initial Rate (M/s)
4.0 x 105
1.6 x 104
8.0 x 105
k [Y] [Z]
k [Y]2 [Z]
k [Y]2 [Z]2
k [Y] [Z]2
k [Y]4 [Z]2
44-Which of the following statements is wrong?
A) Reactions proceed faster if the surface area is increased.
B) The reaction rate is the ratio between the change in concentration
and the change in time.
C) A catalyst increases the overall activation energy of a chemical
reaction.
D) In general, as the temperature increases, the reaction rate
increases.
E) The half-life of a first order reaction is independent of the initial
concentration.
45- For the 1st order reaction:
2N2O5(g)  4NO2(g) + O2(g)
The following data were collected:
Time (minutes)
[N2O5] (mol/L)
0
1.24 x 102
10
0.92 x 102
20
0.68 x 102
30
0.50 x 102
40
0.37 x 102
50
0.28 x 102
70
0.15 x 102
The half-life of this reaction is approximately ______ minutes.
A)
B)
C)
D)
E)
15
18
23
36
45
46- The reaction: 2SO2(g) + O2(g)  2SO3(g) at 298K has a standard
entropy change of -189.6 J/mole. The standard enthalpy formation of SO2 = 296.9 kJ/mole, and SO3 = -395.2 kJ/mole. Estimate the value of the standard
free energy change at 298 K for this reaction in kJ.
A)
B)
C)
D)
E)
273.15
–273.15
–140.4
–196.6
insufficient data
47-Which of the following reactions has a positive S?
A)
B)
C)
D)
E)
2H2(g) + O2(g)  2H2O(g)
2NO2(g)  N2O4(g)
H+(aq) + F(aq)  HF(aq)
2O3(g)  3O2(g)
2Hg(ℓ) + O2(g)  2HgO(s)
48-For AgI, Ksp = 1.5 x 1016. If you mix 500.0 mL of 1.0 x 108 M AgNO3 and
500.0 mL of 1.0 x 108 M NaI, what will be observed?
A)
B)
C)
D)
E)
A precipitate forms because Q > Ksp
A precipitate forms because Q < Ksp
No precipitate forms because Q = Ksp
No precipitate forms because Q < Ksp
No precipitate forms because Q > Ksp