CHEM 1031 - PRACTICE EXAM I - CLASS - SPRING 2017 ANSWER KEY
1. At room temperature, one football weighs 22.5 g and a second football weighs 23.1 g. This
statement is best described as a
A) theory
B) qualitative observation
C) law
D) quantitative observation
2. A cube of solid Au has a mass of 53.1 g and Au has a density of 19.32 g/cm3. What is the
length of a side of the cube in centimeters?
A) 1.40
B) 2.75
C) 1025
D) 2.05
3. A different sample of Au weighs 1.562 x 10-4 g, how much does it weigh in micrograms?
B) 1.562 x 10-10
A) 15.62
C) 156.2
C) 1.562 x 106
4. A 10.0 g sample of CO2 is found to have a ratio of O to C of 2.66. A 25.0 g sample of CO2 is
found to have ratio of O to C of 2.66. This is an example of the law of
A) conservation of mass B) definite proportions C) multiple proportions D) none of the above
5. J.J. Thomson’s cathode ray experiment did not identify what about electrons:
A) electrons are negatively charge
C) the charge-to-mass ratio of an electron
B) the numerical value of charge of an electron
D) cathode ray was produced by many elements
6. A scientist repeats Milliken’s oil drop experiment finding a drop of oil has a charge of
-3.2 x 10-19 coulombs. How many electrons are added to the oil drop?
A) 5
B) 10
C) 2
D) 1
7. Rutherford’s gold foil experiment discovered what about the atom?
A) most of the mass was found in the nucleus
C) Both A or B
B) the nucleus was negatively charged
D) none of the above
8. Select the subatomic particle(s) found in the nucleus of an atom
A) proton
B) proton, electron C) neutron
D) proton, neutron E) proton, neutron, electron
9. An imaginary element, Wentzonium, has 2 stable isotopes, 121Wz (122.132 amu) and 124Wz
(123.904 amu). The natural abundance is 23.12 % of 121Wz and 76.88 % of 124Wz. What is the
average atomic mass of Wentzonium?
A) 123.500
B) 122.132
C) 123.904
D) 123.494
10. The number of protons, neutrons, and electrons in the ion formed by 27Al are
A) 13, 14, 10
B) 13, 27, 13
C) 10, 14, 10
D) 13, 27, 10
11. What is the mass of 1.974 x 1023 atoms of copper in grams?
A) 20.83
B) 1.87 x 1045
C) 25.83
D) 1.25 x 1025
12. What is the percent mass of nitrogen in Mg(NO3)2?
A) 16.4 %
B) 64.7 %
C) 18.9 %
D) 22.2 %
13. What is the mass of nitrogen in a 8.14 g sample of Mg(NO3)2 in grams?
A) 0.58
B) 1.54
C) 1.81
D) 3.44
14. What is the charge of titanium in the compound, TiS ?
A) Ti2+
B) Ti4+
C) Ti2-
D) Not enough information
15. Ammonium nitrate is a(n) _____ compound
A) covalent compound
B) ionic compound C) heterogeneous mixture D) homogeneous mixture
16. N2O5 is a(n) ____ compound and is named _____.
A) ionic, dinitrogen pentoxide
C) molecular, nitrogen (V) oxide
B) ionic, nitrogen (V) oxide
D) molecular, dinitrogen pentoxide
17. A compound containing Fe2+ and chlorine would have what formula unit
A) Fe2Cl3
B) FeCl3
C) FeCl2
D) Fe(ClO)2
18. The formula for the compound formed between barium and carbonate ions is
A) BaCO3
B) Ba2(CO3)3
C) BaC
D) BaPO4
19. The name of the compound from question 18 is
A) barium(I) carbonate
C) barium carbonate
B) barium(III) carbonate
D) dibarium tricarbonate
20. What is the name of the H2CO3 ?
A) dihydro carbonate
C) hydrocarbonic acid
B) carbonic acid
D) hydrogen carbon oxide
21. A 7.36 g sample of an unknown compound contains 54.53% C, 9.15% H, and 36.32% O.
Calculate the empirical formula of the unknown compound.
A) C6HO4
B) CHO
C) C2H4O
D) C4H8O2
22. If the molar mass of the compound in Question 21 is determined to be 176.21 g/mol, what
is the molecular formula?
A) C2H4O
B) C8H16O4
C) C2H4O
D) C4H8O2
23. Balance the following chemical equation:
a sodium phosphate + b calcium sulfide  c sodium sulfide + d calcium phosphate
A) 3,2,1,3
B) 2,2,6,1
C) 2,1,1,2
D) 2,3,3,1
24. Balance the following chemical equation:
a phosphorus pentafluoride + b dihydrogen monoxide  c phosphoric acid + d hydrofluoric acid
A) 1,1,1,1
B) 1,4,1,5
C) 2,4,1,5
D) 2,5,2,10
25. The reaction from question 24 occurred and produced 10.0 g phosphoric acid, which
represents a 92.5 % yield. Calculate the theoretical yield of the reaction.
A) 9.25 g
B) 11.3 g
C) 10.8 g
D) none of these is correct
26. Assume dihydrogen monoxide is the limiting reactant in the reaction from question 24.
Calculate the mass of dihydrogen monoxide that was used in the reaction.
A) 5.74 g
B) 8.00 g
C) 7.94 g
D) 1.84 g
27. If correctly measured and calculated, a percent yield cannot exceed 100.%
A) true
B) false
Problem A: A reaction between elemental aluminum and elemental oxygen produced
aluminum oxide. Using this information, please answer the below questions:
(a) What type of compounds are each of the reactants and the product (molecular, ionic, etc)?
(b) What is the balanced chemical reaction?
(c) Based on what you know about the law of conservation of mass, what must be true about the
reaction?
(a) Al is an atomic element, O2 is a diatomic element, Al2O3 is an ionic compound
(b) 4 Al + 3 O2  2 Al2O3
(c) The law of conservation of mass would require that the mass of Al and O 2 equals the mass of
Al2O3.
Problem B: A 530.5 g sample of C3H8 gas was combusted in 275.3 g of oxygen. Using this
information, please answer the below questions:
(a) What is the balanced chemical formula?
(b) What is the limiting reactant?
(c) What is the theoretical yield of carbon dioxide?
(a) C3H8 + 5 O2  3 CO2 + 4 H2O
(b) O2 is the limiting reactant
(c) 227.2 g CO2 is the theoretical yield
BONUS: Within 10 years (either way) in what year did J.J. Thomson publish his cathode-ray
tube experiments? 1896 (1886-1906 acceptable answers)
Useful information
NAv = 6.02 x 1023 mole-1
charge e- = -1.6x10-19 C