122H, Chemistry Section 1 Exam 1, S06
INSTRUCTIONS - YOU MUST: SHOW YOUR WORK CLEARLY in the spaces provided for each question. Use unit analysis and round all numerical answers to the correct number of significant figures. Use pencil and erase mistakes. FAILURE TO DO THIS WILL RESULT IN REDUCED OR ZERO CREDIT. Please keep your eyes on your own paper and your answers covered. Use the back of this page for scratch paper. I will not grade anything on this page. Turn in the entire exam when you are done. GOOD LUCK !!
USEFUL INFORMATION Standard Molar Enthalpies of Formation (kJ/mol) CH4(g) 75 CO2(g) 394 NO2(g) 33.2 H2O(g) 242 H2O(l) 286 NH3(g) 46 Mg(OH)2(s) 602 CO(g) 111
h= c= 1 mole = R=
6.626 x 10-34 J sec/photon 2.998 x 108 m/sec 6.02 x 1023 things 0.0821 L atm/mol K = 8.314 J/mol K
1m= 1 Hz = 1 mile = 1 atm = 1 kg = 1 cal =
109 nm 1 sec-1 5280 ft 760 mm Hg 2.20 lb 4.184 J
Magnesium Lead Graphite Methanol Water
Csp (J/g0) 1.02 0.159 0.711 2.55 4.184
PERIODIC TABLE OF THE ELEMENTS
1A
1
2A
3B
4B
5B
6B
7B
8B
8B
8B
1B
2B
3A
4A
5A
6A
7A
8A
2
H
4
He
4.003
1.008
3
Li
6.939
Be
9.012
5
B
6
C
7
N P
8
O S
9
F
10
Ne
20.18
10.81
12.01
14.01
16.00
19.00
11
Na
22.99
12
Mg
24.31
13
Al
26.98
14
Si
28.09
15
16
17
Cl
35.45
18
Ar
39.95
30.97
32.07
19
K
20
Ca
40.08
21
Sc
44.96
22
Ti
47.90
23
V
24
Cr
52.00
25
Mn
54.94
26
Fe
55.85
27
Co
58.93
28
Ni
58.71
29
Cu
63.55
30
Zn
65.39
31
Ga
69.72
32
Ge
72.61
33
As
74.92
34
Se
78.96
35
Br
79.90
36
Kr
83.80
39.10
50.94
37
Rb
85.47
38
Sr
87.62
39
Y
40
Zr
91.22
41
Nb
92.91
42
Mo
95.94
43
Tc
(99)
44
Ru
101.1
45
Rh
102.9
46
Pd
106.4
47
Ag
107.9
48
Cd
112.4
49
In
114.8
50
Sn
118.7
51
Sb
121.8
52
Te
127.6
53
I
54
Xe
131.3
88.91
126.9
55
Cs
132.9
56
Ba
137.3
57
La
138.9
72
Hf
178.5
73
Ta
181.0
74
W
75
Re
186.2
76
Os
190.2
77
Ir
192.2
78
Pt
195.1
79
Au
197.0
80
Hg
200.6
81
Tl
204.4
82
Pb
207.2
83
Bi
209.0
84
Po
(209)
85
At
(210)
86
Rn
(222)
183.8
87
Fr
(223)
88
Ra
226.0
89
Ac
227.0
104
105
106
107
108
109
Unq
(261)
Unp
(262)
Unh
(263)
Uns
(262)
Uno
(265)
Une
(266)
FIRST NAME________________________ Exam 1, S06
LAST NAME________________________ PLEASE USE PENCIL !!!
1. Please fill out the following table. Chemical Name calcium phosphide ____________ ammonium nitrite Formula ____________ NCl3 ____________
2. The reaction between nitrogen dioxide and fluorine is first order in nitrogen dioxide and first order in fluorine. 2NO2 + F2 -------> 2 NO2F Propose a two step mechanism where the first step is slow that is consistent with this rate law. Step 1:
Step 2:
3. Radioactive gold, 198Au, is used in the diagnosis of liver problems and has a half-life of 2.69 days. If you are initially given 3.40 mg of the isotope, how long will it take for it to decay to 0.00100 mg ?
Exam 1, S06
Page 2
4. A Meals Ready to Eat packet, MRE, uses the reaction below to heat food on the battle field. Based on standard heats of formation, calculate the amount of energy generated when magnesium and water react.
(You may just show the calculation and answer for this question. No detailed work necessary)
Mg(s) + 2H2O(l) ------> Mg(OH)2(s) + H2(g)
5. The kinetics of the dimerization of tetrafluoroethylene to octafluorocyclobutane were studied at 450 K and the following data were obtained. Time (sec) 0 6 18 35 48 72 [C2F4] (M) 0.64 0.55 0.42 0.32 0.27 0.21
2 C2F4(g) ----> C4F8(g)
A. Use the half-life method to determine if this reaction is 0th, 1st, or 2nd order.
YOU MUST SHOW YOUR WORK CLEARLY IN THE SPACE BELOW TO RECEIVE CREDIT FOR THIS PROBLEM.
B. What would you plot to confirm this ? C. How could you get the rate constant ?
X - Axis
___________
Y-Axis _____________
Exam 1, S06
Page 3
6. The reaction between mercury(II) chloride and oxalate ion has been studied at 250C and the following data were collected in moles of CO2(g)/L min. 2 HgCl2 + C2O42 Experiment 1 2 3
-----> Hg2Cl2
+ 2 Cl + 2CO2(g) Rate of Appearance of Hg2Cl2 (M/min) -6 8.90 x 10 -5 8.01 x 10 -5 3.56 x 10
[HgCl2]o M 0.0520 0.0520 0.208
[C2O42] o M 0.150 0.450 0.150
YOU MUST SHOW YOUR WORK CLEARLY IN THE SPACES BELOW TO RECEIVE CREDIT FOR THIS PROBLEM.
A. The order with respect to [HgCl2] is ____________ .
B. order The with respect to [C2O42] is ____________ .
C. The rate law for this reaction is _____________________________ .
7A. What thermodynamic quantity is measured in a bomb calorimetry experiment ?
B. Show how this quantity is obtained from the First Law of Thermodynamics.
Exam 1, S06
Page 4
8A. In class I sprinkled iron filings into a flame. You observed ______________________ B. This was to illustrate (JUST A FEW WORDS ARE NECESSARY):
9. In the General Mills laboratory a nutritionist measured the calorie content of the newest taste sensation, blue cheese pizza. She found that when a 0.567g sample of homogenized freeze-dried pizza was burned in a bomb calorimeter the temperature increased from 22.730C to 27.350C. The calorimeter contained 525.4 g water. The heat capacity of the calorimeter was found in a separate experiment to be 377.3 J/0C. Calculate the number of food calories (kcal) per slice of pizza where one slice weighs 117 grams.
Exam 1, S06
Page 5
10. In class I demonstrated the decomposition of hydrogen peroxide catalyzed by iodide ion. I 2 H2O2 (aq) ---------> 2 H2O (l) + O2 (g) A. The reaction is found to be first order in hydrogen peroxide and second order in iodide ion. The rate law for this reaction is ______________________________ . B. If the concentration of iodide ion is increased from 0.05 M to 0.25 M the reaction rate will increase by a factor of _______________________
The kinetics of this reaction were studied and the following data were obtained:
Decomposition of H2O2
Time (sec) 0 400 800 1200 2400
[H2O2] (M) 2.32 1.72 1.30 0.98 0.39
2.50 2.00 1.50 1.00 0.50 0.00 0 500 1000 1500 t (seconds) 2000 2500 3000
C. The instantaneous rate at 400 seconds is _______________ . (BE SURE TO SHOW YOUR WORK CLEARLY !)
11. Write the standard formation reaction for lithium phosphate. Indicate the state (s, l, g, aq) for each substance.
Exam 1, S06
Page 6
12. The experimentally determined rate law for the reaction between hydrogen gas and nitrogen monoxide is: 2 Rate = k [H2][ NO] Overall reaction: 2 H2(g) + 2 NO(g) ---------> N2(g) + 2 H2O(g) H0 = 664 kJ/mol A. Derive a rate law for this reaction using the following mechanism. Step 1: 2 NO <----> N2O2 Fast equilibrium Step 2: N2O2 + H2 ----> N2O + H2O Slow Step 3: N2O + H2 ----> N2 + H2O Fast
B. Does this rate law agree with the experimentally determined one ?
YES
NO
(CIRCLE ONE)
C. Circle below all substances that are reactive intermediates in the proposed mechanism NO, N2O2, H2 , N2O , H2O , N2, There are no reactive intermediates D. Circle below all substances that ar...