CHEM 1332
SPRING 2004
FIRST EXAM - FEBRUARY, 20th – Version 1
1.
For the following types of bonding or non-bonding (intermolecular) forces, rank them from the strongest (first) to weakest
(last): Ion-dipole; H bond; dispersion (London); ionic
(A)
(C)
(E)
ion-dipole, H bond, dispersion (London), ionic
ionic, dispersion(London), H-bond, ion-dipole
H bond, ion-dipole, dispersion (London), ionic
2.
In a standard phase diagram that plots temperature versus pressure, which one of the following statements is TRUE?
(A)
(B)
(C)
(D)
(E)
Three phases coexist at equilibrium at any point along one of the lines that separate regions (areas) on the phase diagram.
Two phases coexist at equilibrium at the triple point on the phase diagram.
The gas-solid line ends at a critical point on the phase diagram, beyond which evaporation cannot occur.
The gas-liquid line ends at the critical point on the phase diagram, beyond which a gas cannot be compressed to form a liquid.
In fact, all the above statements are false.
3.
Consider the compounds CH3OH, CCl4, and CH3Br. For each compound, list the strongest intermolecular force that operates
within a sample of that compound.
(A)
H-bonding is the strongest intermolecular force in CH3OH, dispersion is the strongest intermolecular force in CCl4, and dipoledipole is the strongest intermolecular force in CH3Br.
Dispersion is the strongest intermolecular force in CH3OH, dispersion is the strongest intermolecular force in CCl4, and
dispersion is the strongest intermolecular force in CH3Br.
Ion-dipole is the strongest intermolecular force in CH3OH, Ion-dipole is the strongest intermolecular force in CCl4, and dipoledipole is the strongest intermolecular force in CH3Br.
Dipole-induced dipole is the strongest intermolecular force in CH3OH, dispersion is the strongest intermolecular force in CCl4,
and dipole-dipole is the strongest intermolecular force in CH3Br.
Ion-induced dipole is the strongest intermolecular force in CH3OH, dispersion is the strongest intermolecular force in CCl4,
and H-bonding is the strongest intermolecular force in CH3Br.
(B)
(C)
(D)
(E)
(B)
(D)
1
ionic, ion-dipole, H bond, dispersion (London)
dispersion (London), ionic, H-bond, ion-dipole
4.
From the data below, calculate the total heat (in J) needed to convert 12.0 g of ice at -5.0 ºC to liquid water at 0.5 ºC:
ΔHfus= 6.02 kJ/mol
csolid = 2.09 J/g y ºC
Melting point 0.0 ºC
cliquid = 4.18 J/g y ºC
(A)
(D)
–2.2 x 103 J
4.2 x 103 J
5.
Which of the following statements is true?
(A)
(B)
(C)
(D)
(E)
An ionic compound with a high lattice energy will probably be soluble in water.
Some mixtures that have an ENDOTHERMIC heat of solution will still form due to a decrease in entropy.
Hydrogen bonding will only occur in a solution for which both the solute and solvent exhibit hydrogen bonding as pure
substances.
The solubility of a gas in a liquid decreases as the external pressure increases.
All of these statements are false.
6.
Which of the following substances should be the most soluble in ethanol (CH3CH2OH)?
(A)
C3H8
7.
Calculate the molarity of an aqueous solution that is 5.20% by mass CaCl2, given that the density of the solution is 1.19 g/mL.
(A)
(D)
6.19 M
0.557 M
8.
Calculate the molality and mole fraction of water, respectively, of a solution that is made by dissolving 3.50 g of potassium
nitrate in 50.0 g of water. The final volume of the solution is 56.0 mL.
(A)
(C)
(E)
6.18 x 10-1 m; 0.935
6.18 x 10-1 m; 0.988
6.93 x 10-1 m; 0.988
(B)
(E)
(B)
Cl2
2.1 x 102 J
2.2 x 103 J
(C)
(B)
(E)
(C)
CaCO3
0.468 M
0.394 M
(D)
(C)
(B)
(D)
2
6.93 x 10-4 m; 0.935
6.93 x 10-1 m; 0.935
–2.1 x 102 J
KCl
(E)
Fe
5.20 M
9.
Which of the following solutions will have the LOWEST freezing point?
(A)
(B)
(C)
(D)
(E)
0.100 M NaCl
0.100 M CaCl2
0.100 M K3PO4
0.100 M C3H8O3
All will have the same freezing point as they are all the same concentration.
10.
Calculate the boiling point of a solution in which 12.8 g of naphthalene (C10H8) is dissolved in 200. g of benzene (C6H6). The
normal boiling point of C6H6 is 80.1 ºC and the value of Kbp = 2.54 ºC/m.
(A)
(D)
81.4 ºC
101.3 ºC
11.
Calculate the osmotic pressure of a solution of glucose that is made by dissolving 10.0 g of glucose (C6H12O6) in enough water
to make 350. mL of solution at 25 ºC.
(A)
(D)
0.159 atm
6.60 atm
12.
222 mg of an unknown biomolecule was dissolved in enough water to produce 58.0 mL of solution. If the osmotic pressure at
30.0 ºC was found to be 11.1 torr, calculate the molar mass of the molecule.
(A)
(D)
6.51 x 106 g/mol
378 g/mol
13.
Which of the following lowers the activation energy of a reaction?
(A)
(C)
(E)
adding reactants
removing products
raising the temperature
(B)
(E)
(B)
(E)
(B)
(E)
80.1 ºC
98.7 ºC
(C)
0.325 atm
3.93 x 102 atm
(C)
8.57 x 103 g/mol
6510 g/mol
(B)
(D)
3
(C)
78.8 ºC
3.88 atm
6.60 x 105 g/mol
lowering the temperature
adding a catalyst
14.
What is the rate law for the following reaction and its mechanism?
2 HgCl2 + C2O42- → 2 Cl- + 2 CO2 + Hg2Cl2 (overall reaction)
HgCl2 + C2O42- → HgCl2C2O42HgCl2C2O42- + C2O42- → Hg + 2 C2O4Cl2Hg + HgCl2 → Hg2Cl2
2 C2O 4Cl2- → C2O42- + 2 Cl- + 2 CO2
Step 1.
Step 2.
Step 3.
Step 4.
(A)
(D)
Rate = k[HgCl2][C2O42-]
Rate = k[HgCl2][C2O42-]2
15.
For 2 NO + O2 → 2NO2, initial rate data are:
(B)
(E)
[NO], M
[O2], M
0.010
0.010
0.030
0.010
0.020
0.020
fast
slow
fast
fast
Rate = k[HgCl2]2[C2O42-]
Rate = k[HgCl2]2[C2O42-]2
(C)
Rate = k[Hg2Cl2]
(C)
second order
initial rate, mM/s
2.5
5.0
45.0
The order with respect to NO is
(A)
(D)
zero order
third order
(B)
(E)
16.
The rate constant for a reaction is k = 0.00073 s-1. What is the percent of reactant that has decomposed after 500 s?
(A)
(D)
69%
31%
(B)
(E)
first order
fourth order
57%
43%
(C)
4
37%
17.
The rate constant for a reaction is k = 0.175 M-1s-1. Which of the following statements is true about this reaction,
I.
II.
III.
IV.
V.
the sum of the exponents in the rate law is equal to one.
The sum of the exponents in the rate law is equal to two.
The sum of the exponents in the rate law is equal to three.
The half-life is not constant,
The half-life is constant.
(A)
(D)
I and IV
1 and V
18.
Substance A decomposes by a first-order reaction. Initially [A] = 2.00 M but after 150 min [A] = 0.50 M. What is the half-life
for this reaction?
(A)
(D)
150 min
15.0 min
19.
A first-order reaction has a half-life of 55.0 min at 25 ºC and 6.8 min at 100 ºC. What is the activation energy for this reaction?
(A)
(D)
–25.8 kJ/mol
25.8 kJ/mol
20.
Which of the following statements is false?
(A)
(B)
(C)
(D)
(E)
In order for a reaction to occur, reactant molecules must collide.
A catalyst alters the rate of a reaction and is neither a product nor a reactant in the overall equation.
According to collision theory, only those collisions with energy greater than Ea can lead to reaction.
Bimolecular reactions involve a collision between three molecules.
The transition state is a short-lived, high energy state, intermediate between reactants and products.
(B)
(E)
(B)
(E)
(B)
(E)
II and IV
III and IV
(C)
37.5 min
300 min
(C)
–38.8 kJ/mol
38.8 kJ/mol
(C)
5
I, III, and V
75.0 min
347 kJ/mol