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Houston Community College System
Chemistry 1413
EXAM # 3
The Periodic Table of the Chemical Elements
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CHEM 1413 Exam #3
Name: __________________
Dr. Violeta Coarfa
Score:
Part I. Multiple choice questions. ( 3 points each)
Direction- Please write your correct choice in space provide.
1. In a solution, the solvent
A) is a liquid.
B) can be a liquid or gas.
C) can be a solid, liquid, or gas.
D) is never a solid.
E) is the substance present in the smallest concentration.
2. Oil does not dissolve in water because
A) oil is polar.
B) oil is nonpolar.
C) water is nonpolar.
D) water is saturated.
E) oil is hydrated.
3. In water, a substance that ionizes partially in solution is called a
A) weak electrolyte.
B) nonelectrolyte.
C) semiconductor.
D) nonconductor.
E) strong electrolyte.
4. Double and triple bonds form because
A) the atoms involved have high electronegativities.
B) one of the atoms in the molecule has more than 8 valence electrons.
C) single covalent bonds do not give all of the atoms in the molecule eight valence electrons.
D) the ions involved have charges larger than one.
E) there is at least one hydrogen atom involved in the bond.
5. The VSEPR theory allows us to determine the
A) charge on an ion.
B) shape of a molecule.
C) color of a compound.
D) bond type for a molecule.
E) formula for a compound.
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6. What is the molarity of a solution containing 10.0 moles of KCl in 4.0 L of solution?
A) 2.5 M
B) 1.0 M
C) 5.0 M
D) 10. M
E) 2.0 M
7. The boron trifluoride molecule is
A) a polar molecule with polar bonds.
B) a nonpolar molecule with polar bonds.
C) a nonpolar molecule with nonpolar bonds.
D) a polar molecule with nonpolar bonds.
E) a polar molecule with ionic bonds.
8. According to the Arrhenius concept, if NH3 is dissolved in water, it would act as
A) a base.
B) an acid.
C) a source of H+ ions.
D) a source of H- ions.
E) a proton donor.
9. According to the Bronsted-Lowry definition,
A) an acid is a proton acceptor.
B) a base produces H + ions in aqueous solutions.
C) a base is a proton donor.
D) a base is a proton acceptor.
E) an acid acts as the solvent10. Double and triple bonds form because
10. The shape of ammonia is
A) linear.
B) tetrahedral.
C) pyramidal.
D) bent
E) octagonal.
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11. The conjugate acid of H 2 O is ________.
A) H 3O +
B) OH 
C) H 2 O
D) O 2 
E) H 2 O has no conjugate base.
12. What is the [ H 3O + ] in a solution with [ OH  ] = 11012 M ?
A) 11012 M
B) 1102 M
C) 1107 M
D) 1108 M
E) 1.0 102 M
13. What is the pH of a solution with [ OH  ] = 1104 M ?
A) 10.0
B) -10.0
C) 4.0
D) -4.0
E) 1.0 1010
14. Which of the following is correctly identified?
A) NH3 , strong acid
B) RbOH, strong base
C) HCl, weak acid
D) H2CO3 , strong acid
E) Ca(OH)2 , weak base
15. The function of a buffer is to
A) change color at the end point of a titration.
B) maintain the pH of a solution.
C) be a strong base.
D) maintain a neutral pH.
E) act as a strong acid
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16. Which of the following could be a buffer?
A) NaF
B) HF + NaF
C) HF + H 2 O
D) NaF + H 2 O
E) NaCl + HF
17. The product from the alpha decay of
A)
235
93
Np
B)
239
94
Pu
C)
231
90
Th
D)
233
80
Ra
E)
236
92
U
235
92
u is ________.
18. The gas with an initial volume of 24.0 L at a pressure of 565 mmHg is compressed until the volume is 16.0
L. What is the final pressure of the gas, assuming the temperature does not change?
A) 377 mmHg
B) 760 mmHg
C) 848 mmHg
D) 500. mmHg
E) 465 mmHg
19. What is the radioactive particle released in the following nuclear equation?
90
38
Sr 
90
39
Y?
A) alpha particle
B) beta particle
C) gamma ray
D) proton
E) neutron
20. At 570. mm Hg and 25 °C, a gas sample has a volume of 2270 mL. What is the final temperature at a
volume of 1250 mL if pressure remains constant?
A) 1560 mm Hg
B) 210 mm Hg
C) 7000 mm Hg
D) 690 mm Hg
E) 470 mm Hg
21. A 5.00-L tank contains helium gas at 1.50 atm. What is the pressure of the gas in mm Hg?
(1 atm = 760 mmHg)
A) 1.50 mm Hg
B) 507 mm Hg
C) 760 mm Hg
D) 1140 mm Hg
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E) 3800 mm Hg .
22. The half-life of a radioisotope is
A) one-half of the time it takes for the radioisotope to completely decay to a nonradioactive isotope.
B) the time it takes for the radioisotope to become an isotope with one-half of the atomic weight of the original
radioisotope.
C) the time it takes for the radioisotope to become an isotope with one-half the atomic number of the original
radioisotope.
D) the time it takes for the radioisotope to lose one-half of its neutrons.
E) the time it takes for one-half of the sample to decay.
23. Iodine-123, which is used for diagnostic imaging in the thyroid, has a half-life of 13 hours. If 50.0 mg of I123 were prepared at 8:00 A.M. on Monday, how many mg remain at 10:00 A.M. on the following day?
A) 50.0 mg
B) 25.0 mg
C) 12.5 mg
D) 6.25 mg
E) 3.13 mg
24.) Complete the following statement: In Charles' law, the volume of a gas ________ when the ________
decreases.
A) increases, temperature
B) increases, quantity of gas
C) increases, pressure
D) decreases, temperature
E) decreases, pressure
25. The half-life of bromine-74 is 25 min. How much of a 4.0 mg sample is still active after 75 min?
A) 0.50 mg
B) 1.0 mg
C) 2.0 mg
D) 0.25 mg
E) 4.0 mg
Part II. Show all your work for complete credit. ( 5 points each)
26) What is the concentration, in m/m%, of a solution prepared from 50.0 g NaCl and 250.0 g of water?
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27. a. Rubbing alcohol is 70.% isopropyl alcohol by volume. How many mL of isopropyl alcohol are in a 1
pint (473 mL) container?
b. What is the concentration, in m/v%, of a solution prepared from 50. g NaCl and 2.5 L of water?
28. What volume of a 0.12 M KOH solution is needed to react with 23. mL of 0.22 M HCl?
The reaction is: KOH  HCl  KCl  H 2 O
29. a. Write the chemical equation for the neutralization of H3PO4 with Ca(OH)2
b. Ba and Cu are put in an aqueous solution of hydrochloric acid. Write the reaction(s) we
have for this situation.
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30. 25.0 mL of 0.212 M NaOH is neutralized by 13.6 mL of an HCl solution. Calculate the molarity of the HCl
solution.
Part III. Bonus Questions. (3 points each). Show your work for full credit!
1. A 10.0 mL of 0.121 M H 2SO4 is neutralized by 17.1 mL of KOH solution. Calculate the molarity of the
KOH solution.
2. How many grams of glucose are needed to prepare 400. mL of a 2.0%(m/v) glucose solution?
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3. Krypton-79 has a half-life of 35 hours. How many half-lives have passed after 105 hours?
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