CHEMISTRY 101 Name ______Hour Exam I September 25, 2018 Signature ______McCarren Section ______

“You cannot hope to build a better world without improving the individuals. To that end each of us must work for his own improvement and at the same time share a general responsibility for all humanity, our particular duty being to aid those to whom we think we can be most useful.” – Marie Curie

This exam contains 17 questions on 9 numbered pages. Check now to make sure you have a complete exam. You have one hour and thirty minutes to complete the exam. Determine the best answer to the first 15 questions and enter these on the special answer sheet. Also, circle your responses in this exam booklet. Show all of your work and provide complete answers to questions 16 and 17.

1-15 (30 pts.) ______

16 (12 pts.) ______

17 (18 pts.) ______

Total (60 pts) ______

Useful Information:

PV = nRT K = C + 273

R = 0.08206 L•atm/mol•K Density = mass / volume

Avogadro’s number = 6.022 × 1023

1 L = 1000 mL

1 atm = 760. torr

Assume atmospheric pressure is 1.00 atm (unless explicitly told otherwise).

Always assume ideal behavior for gases (unless explicitly told otherwise).

Exam I, Fall 2018 Page 2

Part 1: Multiple Choice Consider the series of molecular diagrams below to answer the next two questions. Assume that each circle represents an atom and the dark and light circles represent atoms of different elements.

1. How many of the diagrams are not mixtures and instead show pure substances? a) 1 b) 2 c) 3 d) 4 e) 5

2. Which two of the diagrams include a molecular element? a) I and IV b) I and VI c) III and VI d) I and V e) III and IV

3. Consider the following formulas for several ionic compounds. For which formula is the cation named correctly? Formula Name a) K3PO4 (I) phosphate b) MnCl2 chloride c) Cu2O (I) d) Co2(SO4)3 (II) sulfate e) ZnS (IV) sulfide

Exam I, Fall 2018 Page 3

4. Consider the following names for several ionic compounds. For how many of the compounds are the formulas written correctly? Name Formula chloride CaCl2 chlorate Ba(ClO3)2 carbonate MgCO3 nitride Sr3N2 Ammonium oxide (NH4)2O

a) 1 b) 2 c) 3 d) 4 e) 5 (All compounds have correct formulas)

5. In which of the following compounds is the number of electrons in the cation identified correctly?

Compound Electrons in Cation

a) CuCl3 29 b) NaBr 12 c) AlP 13

d) LiF 10 e) KNO3 18 6. A compound is 82.6% by mass and the rest . What is its empirical formula? a) CH3 b) C2H5 c) CH2 d) CH5 e) C2H4

7. An unknown compound containing only and has a of 90.0 g/mol. How many of the following have the same empirical formula as this compound? I. Nitrogen monoxide II. III. Dinitrogen dioxide IV. Dinitrogen monoxide V. Trinitrogen hexoxide

a) 1 b) 2 c) 3 d) 4 e) 5 (all have same empirical) Exam I, Fall 2018 Page 4

In the first part of your “Empirical and Molecular Formula” lab activity, you measured the mass of a piece of aluminum foil and calculated the number of atoms it contained. Use this idea to answer the next two questions. 8. A particular sheet of aluminum foil has mass 7.60 g. How many atoms of aluminum are in this foil? a) 0.282 atoms Al b) 1.70×1023 atoms Al c) 7.60×1023 atoms Al d) 4.58×1024 atoms Al e) 1.23×1026 atoms Al

9. The sheet of aluminum foil with mass of 7.60 g has the same number of atoms as another sheet of a different element. This new sheet has a mass of 33.4 grams. What is the sheet of the other element made of? a) Sn b) Cu c) Li d) Ag e) Cs

10. In the second part of your “Empirical & Molecular Formula” lab, you measured mass percentages of various compounds using hypothetical elements A and B. A hypothetical compound has formula AB and is 40% B by mass. If element A is magnesium, what is the identity of element B? a) oxygen b) c) d) e) potassium

11. A gas at constant temperature occupies a volume of 9.94 L and exerts a pressure of 890. torr. What volume (in L) will the gas occupy at a pressure of 510. torr? a) 5.70 L b) 17.3 L c) 1730 L d) 5700 L e) 13,200 L

Exam I, Fall 2018 Page 5

12. A 25.0 L gas tank holds 200. g of argon gas at a pressure of 5.0 atm. What is the temperature of the gas in the container (in C)? a) -265C b) 0.131C c) 7.61C d) 31.5C e) 305 C

13. A closed, rigid container of gas is present at 25C and some initial pressure. The temperature of gas increases to 75.C. How does the final pressure (P2) in the container compare to the initial pressure (P1)? a) P2 is three times P1. b) P2 is greater than twice P1 but less than three times as great as P1. c) P2 is twice P1. d) P2 is greater than P1 but less than twice as great. e) P2 is equal to P1.

14. An empty gas tank has a mass of 5,000. grams. A typical 3.5 liter tank like the one shown to the right holds an unknown gas at a pressure of 138 atm. The gas is at room temperature of 22.0C. The mass of the gas and tank together is 5,880 grams. Which gas is present in the container? a) (CO2) b) Fluorine (F2) c) Oxygen (O2) d) Argon (Ar) e) Helium (He)

15. In your “Explorations with Gases” lab, you held a ‘hand boiler’ and made observations. Which best explains why the bubbles appeared and the liquid rose after holding the hand boiler?

Due to the heat from your hand…. a) the liquid increases temperature to its boiling point and it begins to vaporize quickly as it moves into the gas phase within the top bulb. b) the molecules in the liquid increase in kinetic energy, and cause the liquid to expand and bubble into the higher bulb. c) the size of the individual gas particles get bigger, increasing the pressure, which cause the gas to bubble and rise in the boiler. d) the kinetic energy of the gas and liquid increase, which causes some of the gas particles to bubble into the higher chamber and return to the liquid state. e) the kinetic energy of the gas particles increases which also increases the pressure on the liquid by the gas, pushing the liquid into the higher chamber and creating bubbles. Exam I, Fall 2018 Page 6

Part 2: Free Response Please write your answers in the spaces below and clearly show all work. 16. Consider the following pairs of substances. Determine which choice in each pair has a greater mass, or if both have equal masses. Explain and/or show work to justify your choice.

Set 1  Choice A consists of 4.0 moles oxygen gas (O2).  Choice B consists of 2.0 moles ozone gas (O3).

Set 2  Choice A is a sample of helium gas contained within a 20.0 ounce bottle. The helium gas has density 0.20 g/L. (1 L = 34 ounces)  Choice B is a sample of 2.0 L of helium gas at 2.0 atm and 25°C.

Please go on to the next page to finish question #16. Exam I, Fall 2018 Page 7

For the following pair of substances, determine which choice contains more oxygen. The samples in choices A and B below both have the same mass. Set 3  Choice A is a sample of .  Choice B is a sample of oxide.

Please go on to question 17 on the next page. Exam I, Fall 2018 Page 8

17. A vacuum chamber, similar to the one seen in lecture, contains 0.50 moles argon gas at room temperature. a. The vacuum chamber is turned on and some of the argon leaves the chamber. As this occurs, determine whether each of the following increases, decreases, or remains the same, considering the argon in the vacuum chamber as the system. Explain your reasoning below using kinetic molecular theory and include a molecular level diagram to support your explanation.

Increase, decrease, or constant? Pressure of argon in chamber

Volume of argon in chamber Temperature of argon in chamber Moles of argon in chamber decrease

b. A balloon containing 0.35 moles nitrogen gas is placed into the original vacuum chamber still holding 0.50 moles of argon and the vacuum pump is turned on. The balloon expands. Fill out the table below stating whether each increases, decreases, or remains constant as the balloon expands, considering the balloon as the system. Then, explain why this happens using kinetic molecular theory.

Increase, decrease, or constant? Pressure inside balloon Temperature inside the balloon Moles of nitrogen inside the balloon Volume of the balloon increase Exam I, Fall 2018 Page 9

The vacuum pump remains on until the balloon pops, at which point only 0.25 moles of argon gas are remaining in the container. The 0.35 moles of nitrogen gas from the original balloon mix with the 0.25 moles argon. a. Determine the partial pressure of the argon gas in the container as well as the total pressure in the container. Assume the temperature of the 10.0 L container is 25.0C.

b. What is the total number of atoms in the container?

STOP This is the end of the exam. Nothing written after this page will be graded.

F2016_Chem_101_LabManual.indd 71

periodic table of the elements

1a 8a 1 key 2 1 h hydrogen 67 he 1 1.008 atomic number symbol helium 2a ho 3a 4a 5a 6a 7a 4.003 3 4 5 6 7 8 9 10 name 164.93 atomic mass 2 Li Be B C n o F ne 2 Carbon nitrogen oxygen Fluorine neon 6.941 9.012 10.81 12.01 14.01 16.00 19.00 20.18

11 12 13 14 15 16 17 18

3 na mg al si P s Cl ar 3 sodium magnesium aluminum sulfur argon 22.99 24.31 3B 4B 5B 6B 7B 8B 8B 8B 1B 2B 26.98 28.09 30.97 32.07 35.45 39.95

19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36

4 k Ca sc ti v Cr mn Fe Co ni Cu Zn Ga Ge as se Br kr 4 Potassium Calcium manganese Cobalt nickel Copper Zinc selenium Bromine krypton 39.10 40.08 44.96 47.88 50.94 52.00 54.94 55.85 58.93 58.69 63.55 65.38 69.72 72.59 74.92 78.96 79.90 83.80

37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54

5 rb sr y Zr nb mo tc ru rh Pd ag Cd in sn sb te i xe 5 strontium molybdenumtechnetium iodine xenon 85.47 87.62 88.91 91.22 92.91 95.94 (98) 101.1 102.9 106.4 107. 9 112.4 114.8 118.7 121.8 127. 6 126.9 131.3

55 56 57 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 6 Cs Ba La hf ta w re os ir Pt au hg tl Pb Bi Po at rn 6 Cesium Barium Platinium Gold Polonium astatine radon 132.90 137. 3 138.9 178.5 180.9 183.9 186.2 190.2 192.2 195.1 197. 0 200.6 204.4 207.2 209.0 (209) (210) (222) 87 88 89 104 105 106 107 108 109 110 111 112 114 116

7 Fr ra ac rf db sg Bh hs mt ds – – – – 7 Francium radium rutherfordium dubnium seaborgium Bohrium hassium meitneriumdarmstadtium — — — — (223) 226 (227) (261) (262) (263) (262) (265) (266) (269) (272) (277) (285) (289)

58 59 60 61 62 63 64 65 66 67 68 69 70 71

Lanthanides 6 Ce Pr nd Pm sm eu Gd tb dy ho er tm yb Lu 6 Praseodymiumneodymium Gadolium holmium 140.115 140.9076 144.24 (145) 150.36 151.965 157.25 158.9253 162.50 164.9303 167.26 168.9342 173.04 174.967 7/27/16 1:32 PM 90 91 92 93 94 95 96 97 98 99 100 101 102 103

actinides 7 th Pa u np Pu am Cm Bk Cf es Fm md no Lr 7 Curium Berkelium Californium einsteinium Fermium mendelevium nobelium Lawrencium 232.0381 231.0359 238.0289 (237) (244) (243) (247) (247) (251) (252) (257) (258) (259) (260) Chem 101 Scratch Paper

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