CHEM 1411 Exam #1 (1,2, and 3)
Name:
_______________
Score
Part I. Multiple choice questions. ( 4 points each)
Direction- Please write your correct choice in space provide.
____1. The distance between carbon atoms in ethylene is 134 picometers. Which of the
following express the distance in meters?
A. 1.34x10-13 m
B. 1.34x10-10 m
C. 1.34x10-7 m
D. 1.34x10-6 m
____ 2. Acetic acid boils at 244.2 0F. What is boiling point in degrees celsius?
A. 167.7 0C
B. 153.4 0C
C. 117.8 0C
D. 103.7 0C
____ 3. Which of the following expressed measurement 52,030.2 m in correct scientific
notation?
A. 5.20302x104 m
B. 5.203x104 m
C. 5.20x104 m
D. 5.2x104 m
____ 4. Select the answer with correct number of decimal places for the following sum.
4.65 g + 2.0 g + 19.6442 g =
A. 26.2942 g
B. 26.29 g
C. 26 g
D. 26.3 g
C. Os
D. I
____ 5. Which of the following is a non-metal?
A. Li
B. Be
____ 6. Bromine is the only non-metal that is liquid at room temperature. Consider the
isotope bromine-81, 3581 Br. Select the combination which list the correct atomic
number, neutron number , and mass number respectively.
A. 35,46,81
B. 35,81,46
C. 81,46,35
D. 46,81,35
____ 7. Which of the following name is correct for given chemical formula?
A. I2O5 , iodine pentoxide
C. PbO , lead(I) oxide
B. LiNO3 , lithium nitrate
D. H2SO4 , hydrosulfuric acid
____ 8. Which of the following chemical formula is not correct for given chemical name?
A. ferric oxide , Fe2O3
B. calcium hydroxide , Ca(OH)2
C. tetrasulfur dinitride , S4N2
D. potassium chlorite , KClO3
____9. What is the mass in grams of 0.250 mole common antiacid, calcium carbonate?
A. 4.00x102 g
C. 4.00x10-2 g
B. 25.0 g
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D. 2.50x10-3 g
____ 10. Which one of the following reactions is not balanced?
A. 2C6H6(l) + 15O2(g)  12CO2(g) + 6H2O(g)
B. B2O3(s) + 6HF(l)  2BF3(g) + 3H2O(l)
C. UO2(g) + 4HF(l)  UF4(s) + 4H2O(l)
D. 2B5H9(l) + 12O2(g)  5B2O3(s) + 9 H2O(g)
____11. Which identification is INCORRECT for the element?
A. Na, sodium
B. S, sulfur
C. P, potassium
D. Zn, zinc
____12. Which of the following is not a chemical change?
A. burning coal
C. boiling an egg
B. making bread rise using baking soda
D. boiling water
____13. Which ion has a -1 charge?
A. CO3
B. HSO3
C. NH4
D. SO4
____14. Which of the following is improperly labeled?
A. Cu- transition metal
C. Br- halogen
B. Mg- alkaline earth metal
D. U- noble gas
____15. How many carbon atoms are in CH3-CH2-COO-CH3
A. 1
B. 2
C. 3
D. 4
Part II. Show all your work for complete credit.
16. The density of mercury , the only metal to exist as liquid at room temperature, is 13.6
g/cm3 . What is the density in pounds per cubic inch (lb/in3) ? ( 1 lb=454 g , 1 in =2.54 cm)
( 8 points)
17. The speed needed to scape the pull of earth,s gravity is 11.3 km/s. What is this speed in
mi/hr ? ( 1 mi=1.6094 km) ( 6 points)
18. Lithium , is used in dry cells and storage batteries and in high temperature lubricants, it
has two naturally occurring isotopes, 6Li and 7Li. Calculate the atomic mass of lithium.
( 8 points)
isotopes isotopic mass(amu) abundance(%)
6
Li
6.01521
7.50
7
Li
7.016003
92.50
2
19. Terphthalic acid , used in the production of polyester fibers and films, is composed of
carbon, hydrogen, and oxygen. when 0.6943 g of acid is subjected to combustion analysis
it produced 1.471 g CO2 and 0.391 g H2O. What is its empirical and molecular formula if
its molar mass is 172 g/mol. ( 8 points)
20. Aluminum reacts with oxygen to produce aluminum oxide which can be used as an
absorbent, desiccant or catalyst for organic reactions. ( 10 points)
4 Al(s) + 3 O2(g)  2 Al2O3(s)
A mixture of 82.4 g of aluminum (M=26.98 g/mol) and 117.65 g of oxygen (M=32.00 g/mol)
is allowed to react.
a) Identify the limiting reactant.
b) Calculate the mass of aluminum oxide formed.
c) Determine the mass of the excess reactant present in the vessel when the reaction is
complete.
d) What is the percentage yield for the reaction if reaction mixture produce 120 g of
aluminum oxide?
Bonus question( 10 points)- show all your work.
a) When 11.2 g CaCO3 reacts with excess hydrochloric acid, as below, 4.61 g of CO2 is
produced. What is the percent yield of CO2? Do not type the units with your answer.
CaCO3(s) + 2 HCl(aq)  CO2(g) + CaCl2 (aq) + H2O(l) (not balanced)
b) Calcium reacts with oxygen to make calcium oxide, CaO. What is the theoretical yield
of CaO(s) that could be prepared from 7.63 g of Ca(s) and 2.56 g of O2(g)?
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CHEM 1411 SAMPLE EXAM # 1 - KEY (1, 2, and 3)
PART-I
1. B (pico = 10 -12 , 134 x 10 -12 m = 1.34 x 10 -10 m)
2. C
C = 5/ 9(F-32) = 5/ 9(244.2 - 32) = 5/ 9(212.2) = 117.9 oC
3. A
4. D sum = 26.2942 g , round off to the least number of decimal point (one), sum = 29.3 g
5. D
6. A
7. B
LiNO3 is Lithium nitrate
8. D
9. B
CaCO3 = 1(40) + 1(12) + 3(16) = 100 g/ml
11. C
P is the symbol for phosphorous
13. B
HSO3‾ (bisulfite)
12. D
potassium chlorate, KClO3
10. C
2H2O(l)
boiling water is a phase change from liquid to vapor
14. D Uranium is an inner transition metal
15. D four carbon atoms
PART-II
1 lb
------------ x
454 g
(2.54 cm)3
------------------ = 0.491 lb/ in3
1 in3
16.
13.6 g
----------- x
cm3
17.
11.3 km
------------- x
sec
18.
Ave. atomic wt. of Li = (7.50/100) (6.01521) + (92.50/100) (7.016003) = 6.95 a.m.u.
19.
mc = (3/11) mCO2 = (3/11)(1.471) = 0.4012 g , mH = (1/9) mH2O = (1/9) (0.391) = 0.0434 g
1 mi
3600 sec
---------------- x ---------------- = 2.53 x 104 mi/hr
1.6094 km
1 hr
mO = m - (mc + mH) = 0.6943 - (0.4012 + 0.0434) = 0.2497 g
C = 0.4012/12 = 0.0334
, 0.0334/0.01561 = 2.14 = 2
H = 0.0434/1 = 0.0434
, 0.0434/0.01561 = 2.78 = 3
O = 0.2497/16 = 0.01561 , 0.01561/0.01561 = 1 = 1
empirical formula is C2H3O = 2(12) + 3(1) + 1(16) = 43
X = ( 172/ 43) = 4
,
(C2H3O)4
or
C8H12O4
4
20a)
(4x27) g
(3x32) g
4 Al
+
(2x102) g
3 O2

2Al2O3
82.4 g
117.65 g
Xg
(82.4) (2) (102)
Al2O3 from Al = ------------------------ = 155.64 g = 156 g
4 x 27
(117.65) (2) (102)
Al2O3 from O2 = ------------------------ = 250.00 g
3 x 32
So, Al produce smaller amount of Al2O3. Al is the limiting reagent.
b)
156 g Al2O3 formed
c)
(4x27) g
4 Al
(3x32) g
+
82.4 g
3 O2

2Al2O3
Xg
(82.4) (3) (32)
-----------------------4 x 27
O2 (excess) = 117.65 - 73.2 g = 44.4 g
O2 used up in the reaction =
=
73.2 g
120
% yield = ----------- x 100 = 77%
156
BONUS QUESTION:
d)
a) CaCO3(s) + 2 HCl(aq)  CO2(g) + CaCl2 (aq) + H2O(l)
(11.2 g, CaCO3) x ( 1 mole CaCO3 / 100 g Mwt. ) ( 1mole CO2 /1 mole CaCO3) (44 g CO2 / 1 mole CO2)
= 4.928 g CO2
% yield = ( g, actual value / g, theoretical value) x 100 = 93.5 %
b)
2 Ca + O2  2 CaO
(7.63 g Ca) (1 mol Ca / 40 g) ( 1 molO2 /2 mol Ca) ( 32 g O2 / 1 mol O2) = 3.052 g O2
3.052 g O2 requried to react woth 7.63 g Ca. Since have only 2.56 g O2 in the reaction, therefore O2 is
limiting reagent.
(2.56 g, O2) ( 1 mol / 32 g O2) ( 2 mol CaO / 1 mol O2) (56 g CaO / 1 mol CaO )
= 8.96 g CaO , theoretical value of CaO
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