CHEM 1305
Exam # 3 (Chap. 9-12)
Name:___________________________
Score:
Multiple choice questions (3 points each)
Direction-Please write your correct choice in space provided
_____1. What is the term for a chemical formula that expresses the simplest whole number ratio
of atoms of each element in a molecule?
A) Atomic formula
B) Elemental formula
C) Empirical formula
D) Molecular formula
_____2. Which of the following is equal to 1.00 mole of substance?
A) 6.02 x 1023 sodium atoms, Na
B) 6.02 x 1023 iodine molecules, I2
23
C) 6.02 x 10 sodium iodide formula units, NaI
D) All of the above
_____3. What is the molar mass of cholesterol, C27H45OH?
A) 30.03g/mol
B) 386.73g/mol
C) 4321.78g/mol
D) 432.79g/mol
_____4. Which of the following gases occupies 22.4 L at STP?
A) 1 mol hydrogen, H2
B) 1 mol nitrogen, N2
C) 1 mol oxygen, O2
D) All of the above.
_____5. Benzene has been used as a solvent for varnishes, waxes, and oils. In 1981 the EPA
listed benzene as a carcinogen. What is the molecular formula of benzene if the empirical
formula is C1H1 and the approximate molar mass is 78g/mol?
A) CHO
B) CH2O
C) CH2O6
D) C6H6
_____6. What principle states that equal volumes of gases, at the same temperature and pressure,
contain equal numbers of molecules?
A) Avogadro’s theory.
B) Law of combining volumes.
C) Law of conservation of mass. D) None of the above
_____7. What term refers to the volume occupied by 1 mol of any gas at STP?
A) Avogadro’s volume
B) Molar volume
C) Standard volume
D) none of the above.
_____8. What is the term for the substance in a chemical reaction that controls the maximum
amount of product?
A) Limiting reactant
B) Limiting product
C) maximum reactant
D) maximum product.
____9. Starting with 3.56g of salicylic acid, a student prepares 1.56g of aspirin. If the calculated
mass of aspirin is 1.88g, what is the percentage yield?
A) 83.0%
B) 89.1%
C) 93.1%
D) 107%
____10. Assuming similar conditions, how many liters of chlorine gas react to produce 2Lof
hydrogen chloride gas? H2(g) + Cl2( g)
2HCl(g)
A) 1L
B) 2L
C) 3L
D) 4L
____11. Which of the following instruments measures atmospheric pressure?
A) Aerometer
B) Barometer
C) Spectrophotometer
D) None of these
____12. Which of the following states that the volume and Kelvin temperature are directly
proportional for a gas at constant pressure?
A) Boyle’s law
B) Charles’ law
C) Dalton’s law
D) Gay-Lussac’s law
____13. What is the term that describes two variables having an opposite relationship; for
example, if one variable doubles, the other variable halves?
A) Directly proportional
B) Inversely proportional
C) Theoretically proportional D) None of the above
____14. If the partial pressure of carbon dioxide gas in a blood capillary is 45mmHg, what is the
pressure expressed in inches of mercury? (760mmHg = 29.9 in. Hg)
A) 0.059 in.Hg
B) 0.87 in. Hg
C) 1.8 in. Hg
D) 4.5 in. Hg
____15. A sample of helium gas is at a pressure of 1.00atm. If both the volume and Kelvin
temperature each double, what is the final pressure?
A) 0.250 atm
B) 0.500 atm
C) 1.00 atm
D) 2.00 atm
____16. What is the term for the valence electrons in a molecule that are shared?
A) Bonding electrons
B) Core electrons
C) Nonbonding electrons D) none of the above
____17. Given the electro negativity values of H (2.1), C (2.5), P (2.1), S (2.5), and I (2.5),
which of the following molecules have polar bonds?
A) carbon tetraiodide, CI4
B) phosphine, PH3
C) carbon disulfide, CS2
D) none of the above
____18. Given the electro negativity values of Br (2.8) and F (4.0), illustrate the polarity in a
bromine monofluoride molecule, BrF, using delta notation.
A) δ+Br-F δ+
B) δ+Br-Fδδδ+
C) Br-F
D) δ-Br-F δ____19. A hydronium ion, H3O+, is produced when a hydrogen ion bonds to a water molecule.
What is the term for the resulting bond?
A) ionic bond
B) nonpolar covalent bond
C) polar covalent bond
D) coordinate covalent bond
____20. Which of the following shows a general increasing trend for electro negativity in the
periodic table?
A) down a group of metals
B) down a group of nonmetals
C) across a series of metals from right to left
D) none of the above
___21. What is the volume occupied by 0.33 mol of nitric oxide, NO, at STP?
A) 0.333L
B) 7.46L
C) 13.4L
D) 67.2L
___22. If the pressure of 50.0mL of oxygen gas at 100oC increases from 735 mm Hg, what is the
final volume when the pressure increased to 925.65mm Hg? Assume temperature is constant.
A) 39.7 mL
B) 48.4 mL C) 50.0 mL
D) 51.7 mL
___23. A 40 mL volume of ethane gas is heated from 25.0oC to 50.0oC. If the pressure remains
constant, what is the final volume?
A) 20.0 mL
B) 36.9 mL C) 40.0 mL
D) 43.4 mL
___24. If a volume of nitric oxide gas at 25.0oC increases from 2.00L to 3.00L, what is the final
celcius temperature? Assume the pressure remains constant.
A) -74oC
B) 17oC
C) 38oC
D) 174oC
___25. A sample of hydrogen sulfide gas, at 25.0oCand 319 mm Hg. If the volume remains
constant, what is the final pressure of the gas at -75.0oC?
A) 106 mm Hg B) 182 mm Hg C) 212 mm Hg
D) 480 mm Hg
Show all your work
1. Lindane is a toxic insecticide that causes dizziness and diarrhea in humans. Find
the molecular formula for lindane given its percentage composition: 24.78% C,
2.08% H, 73.14% Cl. The approximate molar mass is 290g/mol
2. If 1.500g of vanadium metal react with oxygen gas to give 2.679g of vanadium
oxide, what is the empirical formula of the product?
3. Galactose and glucose compose lactose, which is referred to as milk sugar. What
is the molecular formula of galactose if the empirical formula is CH2O, and the
approximate molar mass is 180g/mol?
4. An emerald gemstone is an impure form of the mineral beryl, Be3Al2Si16O18.
What is the percentage of beryllium in the mineral?
5. In an experiment, 1.202g of carbon reacts with 6.414g of powered sulfur. Using
the conservation of mass law, predict the mass of product
6. How many moles of hydrogen gas are produced from 0.500 mol of water?
Ca(s) + 2H2O(l)
Ca(OH) 2(g) + H2(g)
7. If a nitrogen gas sample occupies a volume of 2.55L at 22.00C and 0.860 atm,
what is the mass of the N2 gas? ( R = 0.0821 L.atm/mol.K)
8. How many moles of ammonia contain 1.51 x 1024 NH3 molecules?
9. Draw the electron dot formula for sulfur trioxide, SO3. How many pairs of
nonbonding electrons are in sulfur trioxide molecule?