CHEM 1332
SUMMER 2005
Test 1 Version 1
1.
Which of the following substances has the highest boiling point?
(A)
(D)
Cl2
NH3
2.
Which of the following intermolecular forces exist in all solid substances?
(A)
(D)
Dispersion forces
Ion-dipole forces
3.
Which solvent will be better able to dissolve the given solute?
(I)
(II)
(III)
HCl(g) in water or hexane (C6H14)
methane (CH4) in water or carbon tetrachloride (CCl4)
NaCl in ethanol (C2H5OH) or in hexane
(A)
(C)
(E)
water, water, hexane
hexane, carbon tetrachloride, hexane
water, water, ethanol
4.
Which of the following statements are true?
(I)
(II)
(III)
A positive heat of formation means that a solution will not form.
The entropy of a solution is ALWAYS greater than the entropy of the separate components.
The solubility of a gas in a liquid always increases with pressure
(A)
III only
(B)
(E)
(B)
(E)
(B)
II and III
CH3Cl
Ne
Dipole-dipole forces
Hydrogen bonding
(B)
(D)
(C)
Ethanol (CH3CH2OH)
(C)
Ion-induced dipole forces
water, carbon tetrachloride, ethanol
hexane, water, ethanol
I and III
1
(C)
(D)
II only
(E)
I only
5.
Commercial concentrated nitric acid is 69.0 % by mass HNO3 and has a density of 1.42 g/mL. Calculate the molarity of
concentrated nitric acid.
(A)
0.156 M
BONUS:
(B)
7.71 M
(C)
11.0 M
(D)
15.6 M
(E)
48.6 M
What about this solution appears to violate something you have been taught? Write your answer on the back of your
scantron
6.
Two solutions are formed, one from adding 10 g of glucose (C6H12O6) to 1 L of water and the other by adding 10 g of sucrose
(C12H22O11) to 1 L of water. Which solution has the
(I)
(II)
(III)
lower vapor pressure
lower freezing point
lower boiling point
(A)
(D)
glucose, sucrose, glucose
sucrose, sucrose, sucrose
7.
How much naphthalene (C10H8, MM = 128 g/mol) must be dissolved in 500. g of benzene (C6H6, MM = 78 g/mol) to produce a
solution that has a freezing point of 0.38 ºC. (You might want to know that the freezing point of benzene is 5.5 ºC and the value of Kf
is 5.12 ºC/m).
(A)
(D)
4.75 g naphthalene
128 g naphthalene
8.
Which of the following aqueous solutions would be expected to have the highest vapor pressure?
(A)
(D)
0.01 m NaCl
0.02 m CaCl2
(B)
(E)
(B)
(E)
(B)
(E)
sucrose, sucrose, glucose
glucose, sucrose, sucrose
9.52 g naphthalene
256 g naphthalene
0.05 m methanol (CH3OH)
0.03 m ethanol (C2H5OH)
2
(C)
(C)
(C)
glucose, glucose, sucrose
64 g naphthalene
0.01 m K2SO4
9.
(A)
6.42 g of an unknown non-electrolytic substance is dissolved in sufficient water to make 225 mL of solution. If the osmotic
pressure at 25.0 ºC is 35.1 torr, calculate the molar mass of the substance.
1.56 x 106g/mol
(B)
2014 g/mol
(C)
15,100 g/mol
(D)
1.28 x 105 g/mol
(E)
1266 g/mol
10.
Consider the reaction, 8 A + 5 B → 8 C + 6 D. If [C] is increasing at the rate of 4 M/s, at what rate is [B] changing (I am being
nasty here!!!)?
(A)
-2.5 M/s
11.
The units of the rate constant for a zero-order reaction could be:
(A)
(D)
M/s
M-2.s-1
12.
For the reaction A(g) + 2B(g) → 2C(g)
Determine the correct rate law for this reaction.
Trial
1
2
3
4
Initial [A]
(mol/L)
0.125
0.375
0.250
0.375
(A)
Rate = k[A]2[B]
13.
The rate constant for the reaction 3A → 4B is 6.00 × 10-3 L mol-1min-1. How long will it take the concentration of A to drop from
0.75 M to 0.25 M?
(A)
5.5 × 10-3 min
(B)
0.40 M/s
(B)
(E)
Initial [B]
(mol/L)
0.200
0.200
0.400
0.400
(B)
(B)
(C)
2.5 M/s
M-1.s-1
None of these
+
2D(g),
(D)
4.0 M/s
(C)
s-1
(E)
6.4 M/s
the following data were collected at constant temperature.
Initial Rate
(mol/(L·min))
7.25
21.75
14.50
21.75
Rate = k[A][B]2
l80 min
(C)
(C)
Rate = k[A][B]
2.2 × 10-3min
3
(D)
(D)
Rate = k[B]
3.0 × 10-3min
(E)
(E)
Rate = k[A]
440 min
14.
For the decomposition reaction 2N2O5(g) → 4NO2(g) + O2(g), the rate constant is 2.80 x 10-3 s-1 at 60 ºC. How long will it take for
75% of the initial N2O5 concentration to decompose?
(A)
0.021 s
15.
The rate law for the change of CH3NC to CH3CN at 800 K is rate = (1300 s-1)[CH3NC]. What is the half-life for this reaction if one
starts with 0.2 M CH3NC?
(A)
5.3 x 10-4 s
(B)
(B)
5.60 x 10-3 s
1.9 x 10-3 s
(C)
(C)
495 s
(D)
3.95 x 10-3 s
(D)
248 s
520 s
(E)
(E)
0.042 s
1920 s
16.
For a given reaction, the value of the activation energy is 51.2 kJ/mol. Given that the rate constant at 25 ºC is 1.55 x 10-3 1/s, what
is the value of the rate constant at 45 ºC in 1/s?
(A)
4.23 x 10-4
17.
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.
A reaction of the form, 2 A + B → products, will usually have a one-step mechanism.
The rate of the bimolecular reaction A + B → products is proportional to the frequency of collisions between A and B.
The transition state is a short-lived, high energy state, intermediate between reactants and products.
18.
The decomposition of N2O(g) in the presence of Cl2 is thought to follow the mechanism shown below. The second step occurs
twice for each occurrence of the first and third steps. Which are the catalysts and which are the intermediates in this mechanism?
1.
2.
3.
Cl2 → 2 Cl
N2O + Cl → N2 + ClO
2 ClO → Cl2 + O2
(A)
(C)
(E)
catalysts: Cl2 and Cl; intermediates: ClO
catalysts: ClO and Cl; intermediates: Cl2
catalysts: Cl2; intermediates: Cl
(B)
1.55 x 10-3
(C)
1.77 x 10-3
(B)
(D)
4
(D)
5.69 x 10-3
catalysts: Cl; intermediates: Cl2
catalysts: Cl2; intermediates: ClO and Cl
(E)
2.63 x 1054
19.
Which of the following mechanisms is consistent with the observed rate law, rate = k[NO2], for the reaction 2 NO2 → 2 NO(g) +
O2(g)?
Mechanism 1:
NO2 + NO2 → N2O4
N2O4 → N2 + 2 O2
N2 + O2 → 2 NO
slow
fast
fast
Mechanism 2
NO2 → N + O2
NO2 + N → N2O2
N2O2 → 2 NO
slow
fast
fast
Mechanism 3
NO2 → NO + O
O + NO2 → NO + O2
slow
fast
(A)
(D)
All 3 mechanisms
Mechanisms 2 and 3 only
(B)
(E)
Mechanisms 1 and 2 only
Mechanism 1 only
20.
The effect of a catalyst is to:
(A)
(B)
(C)
(D)
(E)
decrease the “effective concentrations of the reactants”
increase the local temperature of the reactants
lower the activation energy of a reaction
increase the energy of the reactants
increase the number of collisions between reactants
5
(C)
Mechanisms 1 and 3 only