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Chemistry Exam 3 for Course CHEM 151: Multiple Choice Questions and Problems, Exams of Chemistry

The third exam for the introductory college chemistry course, chem 151. The exam consists of 23 questions, including multiple choice questions and problems. Topics covered include ionic compounds, lewis structures, molecular shapes, hybrid orbitals, and bonding in diatomic molecules. Students are required to use the periodic table and show their work for problems.

Typology: Exams

2009/2010

Uploaded on 08/14/2010

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NAME (write legibly) _________________
CHEMISTRY 151
EXAM 3
Dr. Hascall 11/19/09
23 questions on pages. DO NOT OPEN UNTIL INSTRUCTED TO DO SO
There is a Periodic Table and other useful information at the end of
the exam. You may detach that page.
It is your responsibility to check that you have all of the pages.
Pay attention to the point value of questions and plan your time accordingly. If
you are not sure how to answer a question, move on to another one and come
back later if you have time.
Show all work on problems and make sure your work and final answer are clear,
and contain appropriate units and numbers of significant figures. Use the backs
of the sheets to make notes.
CHEATING IN ANY FORM WILL NOT BE TOLERATED
Good luck!
pf3
pf4
pf5

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Download Chemistry Exam 3 for Course CHEM 151: Multiple Choice Questions and Problems and more Exams Chemistry in PDF only on Docsity!

NAME (write legibly) _________________

CHEMISTRY 151

EXAM 3

Dr. Hascall 11/19/

23 questions on pages. DO NOT OPEN UNTIL INSTRUCTED TO DO SO

  • There is a Periodic Table and other useful information at the end of the exam. You may detach that page.
  • It is your responsibility to check that you have all of the pages.
  • Pay attention to the point value of questions and plan your time accordingly. If you are not sure how to answer a question, move on to another one and come back later if you have time.
  • Show all work on problems and make sure your work and final answer are clear, and contain appropriate units and numbers of significant figures. Use the backs of the sheets to make notes.
  • CHEATING IN ANY FORM WILL NOT BE TOLERATED
  • Good luck!

1 – 18 Multiple choice questions (3 pts each): Bubble in the correct answer on the Scantron.

  1. Which of these compounds is most likely to be ionic? (a) BaCl 2 (b) CO (c) SO 2 (d) SF 4
  2. Which of these bonds would be considered polar covalent? (a) Na–Cl (b) Cl–Cl (c) S–Cl (d) Na–S
  3. On the Lewis structure of the bromate ion shown at right, the formal charge of the bromine atom is: (a) – 2 (b) – 1 (c) 0 (d) +
  4. Which of these molecules contains an atom that does not obey the octet rule? (a) CO 2 (b) Cl 2 (c) SF 4 (d) NF 3
  5. Complete this statement: A double bond is __________ than a single bond: (a) longer and stronger (b) longer and weaker (c) shorter and stronger (d) shorter and weaker
  6. Which of these elements has the greatest electronegativity? (a) Mg (b) Si (c) Ge (d) Ba
  7. Which of these molecules is polar? (a) CH 4 (b) CF 4 (c) CO 2 (d) CH 2 Cl 2
  8. What type of orbitals overlap to form π bonds? (a) s (b) p (c) sp (d) sp^2 Br O O O
  1. If 9.0 L of NO reacts with excess O 2 at STP, what volume (in L) of NO 2 is produced? 2 NO ( g ) + O 2 ( g ) → 2 NO 2 ( g ) (a) 9.0 L (b) 4.5 L (c) 18 L (d) 6.2 L

  2. Which of these gases has the greatest average molecular speed at 25 °C? (a) Kr (b) Cl 2 (c) Ar (d) All would have the same average speed.

  3. Which of these gas molecules has the highest average kinetic energy at 25 °C? (a) H 2 (b) O 2 (c) N 2 (d) All would have the same average kinetic energy.

  4. (5 pts each) In each case draw a Lewis structure and sketch or name the molecule’s 3D shape, then state if the molecule is polar. (a) PF 5 (b) NF 3

  5. (6 pts) On the figure below, sketch the orbitals involved in the C=C double bond, showing how they overlap. Label the σ and π bonds.

C C

21 – 23: Problems: Show your work clearly!

  1. (12 pts) 0.293 g of a liquid hydrocarbon with the empirical formula CH was vaporized in a flask with a volume of 185 mL. Its pressure was 374 mmHg at 23 °C. What is the molecular formula of this compound? Be sure to show all your calculations.
  2. (8 pts) 1.03 g of zinc metal reacts with excess hydrochloric acid. What volume of hydrogen gas, at standard temperature and pressure (STP), would be produced? Zn ( s ) + 2 HCl ( aq ) → ZnCl 2 ( aq ) + H 2 ( g )

Equations and Constants:H^0 rxn = ∑ BE (reactants) – ∑ BE (products) Pressure units: 1 atm = 760 mmHg = 14.7 psi = 101325 Pa PV = nRT R = 0. Volume of 1 mol ideal gas at STP = 22.4 L KE = KE = €

RT u rms = €

3 RT

M

rate 1 rate 2

M 2

M 1

P total = P 1 + P 2 +... + P n P 1 = χ 1 × Ptotal

L • atm mol• K